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9-2      ENGINES                                                                                            ZJminutes). Th...
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ZJ                                                                                              ENGINES       9-7CYLINDER ...
9-8      ENGINES                                                                                            ZJ  filter run...
ZJ                                   ENGINES   9-9     SERVICE DIAGNOSIS—PERFORMANCE
9 - 10   ENGINES                                  ZJ                   SERVICE DIAGNOSIS—MECHANICAL
ZJ                                   ENGINES   9 - 11     SERVICE DIAGNOSIS—LUBRICATION
9 - 12        4.0L ENGINE                                                                                                 ...
ZJ                                                                                    4.0L ENGINE      9 - 13  (1) 1st Dig...
9 - 14     4.0L ENGINE                                                                                        ZJ          ...
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9 - 16   4.0L ENGINE                                                                                       ZJ             ...
ZJ                                                                                       4.0L ENGINE       9 - 17   (21) C...
9 - 18   4.0L ENGINE                                                                                      ZJ (3) Connect t...
ZJ                                                                                    4.0L ENGINE      9 - 19  (8) Tap the...
9 - 20    4.0L ENGINE                                                                                         ZJINSPECTION...
ZJ                                                                                      4.0L ENGINE       9 - 21  (6) Remo...
9 - 22    4.0L ENGINE                                                                                      ZJ• Bolts 1 thr...
ZJ                                                                                    4.0L ENGINE       9 - 23INSPECTION  ...
9 - 24   4.0L ENGINE                                                                                      ZJ              ...
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  1. 1. ZJ ENGINES 9-1 ENGINES CONTENTS page pageLUBRICATION SYSTEM . . . . . . . . . . . . . . . . . . . 32 5.2L ENGINE SERVICE PROCEDURES . . . . . . . 49LUBRICATION SYSTEM . . . . . . . . . . . . . . . . . . . 65 ENGINE DIAGNOSIS . . . . . . . . . . . . . . . . . . . . . . 64.0L ENGINE SERVICE PROCEDURES . . . . . . . 12 STANDARD SERVICE PROCEDURES . . . . . . . . . 1 STANDARD SERVICE PROCEDURES INDEX page pageEngine Performance . . . . . . . . . . . . . . . . . . . . . . . . 2 Measuring with Plastigage . . . . . . . . . . . . . . . . . . . . 3Form-In-Place Gaskets . . . . . . . . . . . . . . . . . . . . . . 1 Repair Damaged or Worn Threads . . . . . . . . . . . . . 4Honing Cylinder Bores . . . . . . . . . . . . . . . . . . . . . . 2 Service Engine Assembly (Short Block)—4.0LHydrostatic Lock . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4FORM-IN-PLACE GASKETS between smooth machined metallic surfaces. It will There are several places where form-in-place gas- not cure if left in the uncovered tube. DO NOT usekets are used on the engine. DO NOT use form-in- on flexible metal flanges.place gasket material unless specified. Caremust be taken when applying form-in-place gaskets. SURFACE PREPARATIONBead size, continuity and location are of great impor- Parts assembled with form-in-place gaskets may betance. Too thin a bead can result in leakage while too disassembled without unusual effort. In some in-much can result in spill-over. A continuous bead of stances, it may be necessary to lightly tap the partthe proper width is essential to obtain a leak-free with a mallet or other suitable tool to break the sealjoint. between the mating surfaces. A flat gasket scraper Two types of form-in-place gasket materials are may also be lightly tapped into the joint but careused in the engine area (Mopar௡ Silicone Rubber Ad- must be taken not to damage the mating surfaces.hesive Sealant and Mopar௡ Gasket Maker). Each Scrape or wire brush all gasket surfaces to removehave different properties and cannot be used inter- all loose material. Inspect stamped parts to ensurechangeably. gasket rails are flat. Flatten rails with a hammer on a flat plate, if required. Gasket surfaces must be freeMOPARா SILICONE RUBBER ADHESIVE of oil and dirt. Make sure the old gasket material isSEALANT removed from blind attaching holes. Mopar௡ Silicone Rubber Adhesive Sealant, nor-mally black in color, is available in 3 ounce tubes. GASKET APPLICATIONMoisture in the air causes the sealant material to Assembling parts using a form-in-place gasket re-cure. This material is normally used on flexible metal quires care.flanges. It has a shelf life of a year and will not prop- Mopar௡ Silicone Rubber Adhesive Sealant shoulderly cure if over aged. Always inspect the package for be applied in a continuous bead approximately 3 mmthe expiration date before use. (0.12 inch) in diameter. All mounting holes must be circled. For corner sealing, a 3 or 6 mm (1/8 or 1/4MOPARா GASKET MAKER inch) drop is placed in the center of the gasket con- Mopar௡ Gasket Maker, normally red in color, is tact area. Uncured sealant may be removed with aavailable in 6 cc tubes. This anaerobic type gasket shop towel. Components should be torqued in placematerial cures in the absence of air when squeezed while the sealant is still wet to the touch (within 10
  2. 2. 9-2 ENGINES ZJminutes). The use of a locating dowel is recom- (j) If cylinder(s) have abnormally low compres-mended during assembly to prevent smearing the sion pressures, repeat steps 4a through 4h.material off location. (k) If the same cylinder(s) repeat an abnormally Mopar௡ Gasket Maker should be applied sparingly low reading, it could indicate the existence of ato one gasket surface. The sealant diameter should problem in the cylinder.be 1.00 mm (0.04 inch) or less. Be certain the mate- The recommended compression pressures arerial surrounds each mounting hole. Excess material to be used only as a guide to diagnosing enginecan easily be wiped off. Components should be problems. An engine should NOT be disassem-torqued in place within 15 minutes. The use of a lo- bled to determine the cause of low compressioncating dowel is recommended during assembly to pre- unless some malfunction is present.vent smearing the material off location. (5) Clean or replace spark plugs as necessary. Ad- just gap (refer to Group 8D, Ignition System for gapENGINE PERFORMANCE adjustment and torque). To provide best vehicle performance and lowest ve- (6) Test resistance of spark plug cables (refer tohicle emissions, it is most important that the tune-up Group 8D, Ignition System).be done accurately. Use the specifications listed on (7) Inspect the primary wire. Test coil output volt-the Vehicle Emission Control Information label found age, primary and secondary resistance. Replace partson the engine compartment hood. as necessary (refer to Group 8D, Ignition System and (1) Test battery specific gravity. Add water, if nec- make necessary adjustment).essary. Clean and tighten battery connections. (2) Test cranking amperage draw (refer to Group (8) Set ignition timing to specifications (refer to8B, Battery/Starter Service for the proper proce- Specification Label on engine compartment hood).dures). (9) Perform a combustion analysis. (3) Tighten the intake manifold bolts (refer to (10) Test fuel pump for pressure (refer to GroupGroup 11, Exhaust System and Intake Manifold for 14, Fuel System for the proper specifications).the proper specifications). (11) Inspect air filter element (refer to Group 0, (4) Perform cylinder compression test: Lubrication and Maintenance for the proper proce- (a) Check engine oil level and add oil, if neces- dure). sary. (12) Inspect crankcase ventilation system (refer to (b) Drive the vehicle until engine reaches normal Group 0, Lubrication and Maintenance for the proper operating temperature. procedure). (c) Select a route free from traffic and other (13) For emission controls refer to Group 25, Emis- forms of congestion, observe all traffic laws and sion Controls System for service procedures. briskly accelerate through the gears several times. (14) Inspect and adjust accessory belt drives (refer The higher engine speed may help clean out valve to Group 7, Cooling System for the proper adjust- seat deposits which can prevent accurate compres- ments). sion readings. (15) Road test vehicle as a final test.CAUTION: DO NOT overspeed the engine. HONING CYLINDER BORES Before honing, stuff plenty of clean shop towels un- (d) Remove all spark plugs from engine. As spark der the bores and over the crankshaft to keep abra- plugs are being removed, check electrodes for ab- sive materials from entering the crankshaft area. normal firing indicators - fouled, hot, oily, etc. (1) Used carefully, the Cylinder Bore Sizing Hone Record cylinder number of spark plug for future C-823 equipped with 220 grit stones, is the best tool reference. for this job. In addition to deglazing, it will reduce (e) Disconnect coil wire from distributor and se- taper and out-of-round as well as removing light cure to good ground to prevent a spark from start- scuffing, scoring or scratches. Usually a few strokes ing a fire. will clean up a bore and maintain the required lim- (f) Be sure throttle blades are fully open during its. the compression check. (g) Insert compression gage adaptor into the CAUTION: DO NOT use rigid type hones to remove No.1 spark plug hole. Crank engine until maximum cylinder wall glaze. pressure is reached on gauge. Record this pressure as No.1 cylinder pressure. (2) Deglazing of the cylinder walls may be done if (h) Repeat Step 4 g for all remaining cylinders. the cylinder bore is straight and round. Use a cylin- (i) Compression should not be less than 689 kPa der surfacing hone, Honing Tool C-3501, equipped (100 psi) and not vary more than 172 kPa (25 psi) with 280 grit stones (C-3501-3810). 20-60 strokes, de- from cylinder to cylinder. pending on the bore condition, will be sufficient to
  3. 3. ZJ ENGINES 9-3provide a satisfactory surface. Using honing oil and the crankshaft. Place a minimum of 0.254 mmC-3501-3880 or a light honing oil available from ma- (0.010 inch) shim between the bearing shell and thejor oil distributors. adjacent bearing cap. Tighten the bolts to 18 N⅐m (13 ft. lbs.) torque.CAUTION: DO NOT use engine or transmission oil, • CHECK NO.1 BEARING: Shim No.2 main bear-mineral spirits or kerosene. ing. • CHECK NO.2 BEARING: Shim No.1 and No.3 (3) Honing should be done by moving the hone up main bearing.and down fast enough to get a crosshatch pattern. • CHECK NO.3 BEARING: Shim No.2 and No.4The hone marks should INTERSECT at 50° to 60° main bearing.for proper seating of rings (Fig. 1). • CHECK NO.4 BEARING: Shim No.3 and No.5 main bearing. • CHECK NO.5 BEARING: Shim No.4 main bear- ing (5.2L). Shim No.4 and No.6 main bearing (4.0L). • CHECK NO.6 BEARING: Shim No.5 and No.7 main bearing (4.0L). • CHECK NO.7 BEARING: Shim No.6 main bear- ing (4.0L). Remove all shims before assembling engine. METHOD - 2 (ALTERNATIVE)—The weight of the crankshaft is supported by a jack under the coun- terweight adjacent to the bearing being checked. (3) Place a piece of Plastigage across the entire width of the bearing cap shell (Fig. 2). Position the Plastigage approximately 6.35 mm (1/4 inch) off cen- ter and away from the oil holes. In addition, suspect Fig. 1 Cylinder Bore Crosshatch Pattern areas can be checked by placing the Plastigage in that area. Tighten the bearing cap bolts of the bear- (4) A controlled hone motor speed between 200 and ing being checked to 108 N⅐m (80 ft. lbs.) torque300 RPM is necessary to obtain the proper cross- (4.0L Engine). Tighten the bearing cap bolts of thehatch angle. The number of up and down strokes per bearing being checked to 115 N⅐m (85 ft. lbs.) torqueminute can be regulated to get the desired 50° to 60° (5.2L Engine). DO NOT rotate the crankshaft orangle. Faster up and down strokes increase the cross- the Plastigage may be smeared, giving inaccu-hatch angle. rate results. (5) After honing, it is necessary that the block becleaned to remove all traces of abrasive. Use a brushto wash parts with a solution of hot water and deter-gent. Dry parts thoroughly. Use a clean, white, lint-free cloth to check that the bore is clean. Oil thebores after cleaning to prevent rusting.MEASURING WITH PLASTIGAGECRANKSHAFT MAIN BEARING CLEARANCE Engine crankshaft bearing clearances can be deter-mined by use of Plastigage, or equivalent. The follow-ing is the recommended procedures for the use ofPlastigage: Fig. 2 Placement of Plastigage in Bearing Shell (1) Remove oil film from surface to be checked. (4) Remove the bearing cap and compare the widthPlastigage is soluble in oil. of the flattened Plastigage with the scale provided on (2) The total clearance of the main bearings can the package (Fig. 3). Plastigage generally comes in 2only be determined by removing the weight of the scales (one scale is in inches and the other is a met-crankshaft. This can be accomplished by either of two ric scale). Locate the band closest to the same width.methods: This band shows the amount of clearance. Differ- METHOD - 1 (PREFERRED)—Shim the bear- ences in readings between the ends indicate theings adjacent to the bearing to be checked. This will amount of taper present. Record all readings takenremove the clearance between upper bearing shell (refer to Engine Specifications).
  4. 4. 9-4 ENGINES ZJ • Tapping the hole with a special Heli-Coil Tap, or equivalent. • Installing an insert into the tapped hole. This brings the hole back to its original thread size. CAUTION: Be sure that the tapped holes maintain the original center line. Heli-Coil tools and inserts are readily available from automotive parts jobbers. Fig. 3 Clearance Measurement SERVICE ENGINE ASSEMBLY (SHORT BLOCK)— (5) Plastigage is available in a variety of clearance 4.0L ENGINEranges. The 0.025-0.076 mm (0.001-0.003 inch) range A service replacement engine assembly (shortis usually the most appropriate for checking engine block) may be installed whenever the original cylin-bearing clearances. der block is defective or damaged beyond repair. It consists of the cylinder block, crankshaft, piston andCONNECTING ROD BEARING CLEARANCE rod assemblies. If needed, the camshaft must be pro- Engine connecting rod bearing clearances can be cured separately and installed before the engine isdetermined by use of Plastigage, or equivalent. The installed in the vehicle.following is the recommended procedures for the use A short block is identified with the letter Sof Plastigage: stamped on the same machined surface where the (1) Remove oil film from surface to be checked. build date code is stamped for complete engine as-Plastigage is soluble in oil. semblies. (2) Place a piece of Plastigage across the entire Installation includes the transfer of componentswidth of the bearing cap shell (Fig. 2). Position the from the defective or damaged original engine. Fol-Plastigage approximately 6.35 mm (1/4 inch) off cen- low the appropriate procedures for cleaning, inspec-ter and away from the oil holes. In addition, suspect tion and torque tightening.areas can be checked by placing the Plastigage in thesuspect area. HYDROSTATIC LOCK (3) The crankshaft must be turned until the con- When an engine is suspected of hydrostatic locknecting rod to be checked starts moving toward the (regardless of what caused the problem), follow thetop of the engine. Only then should the rod cap with steps below.Plastigage in place be assembled. Tighten the 4.0L (1) Preform the Fuel Pressure Release Procedurerod cap nut to 45 N⅐m (33 ft. lbs.) torque. Tighten the (refer to Group 14, Fuel System).5.2L rod cap nut to 61 N⅐m (45 ft. lbs.) torque. DO (2) Disconnect the negative cable from the battery.NOT rotate the crankshaft or the Plastigage (3) Inspect air cleaner, induction system and in-may be smeared, giving inaccurate results. take manifold to ensure system is dry and clear of foreign material. (4) Remove the bearing cap and compare the width (4) Place a shop towel around the spark plugs toof the flattened Plastigage with the scale provided on catch any fluid that may possibly be under pressurethe package (Fig. 3). Plastigage generally comes in 2 in the cylinder head. Remove the plugs from the en-scales (one scale is in inches and the other is a met- gine.ric scale). Locate the band closest to the same width.This band shows the amount of clearance. Differ- CAUTION: DO NOT use the starter motor to rotateences in readings between the ends indicate the the crankshaft. Severe damage could occur.amount of taper present. Record all readings taken(refer to Engine Specifications). (5) With all spark plugs removed, rotate the crank- (5) Plastigage is available in a variety of clearance shaft using a breaker bar and socket.ranges. The 0.025-0.076 mm (0.001-0.003 inch) range (6) Identify the fluid in the cylinders (coolant, fuel,is usually the most appropriate for checking engine oil, etc.).bearing clearances. (7) Make sure all fluid has been removed from the cylinders.REPAIR DAMAGED OR WORN THREADS (8) Repair engine or components as necessary to Damaged or worn threads can be repaired. Essen- prevent this problem from occurring again.tially, this repair consists of: (9) Squirt engine oil into the cylinders to lubricate• Drilling out worn or damaged threads. the walls. This will prevent damage on restart.
  5. 5. ZJ ENGINES 9-5 (10) Install new spark plugs. Tighten the 4.0L en- (13) Install a new oil filter.gine spark plugs to 37 N⅐m (27 ft. lbs.) torque. (14) Fill engine crankcase with the specifiedTighten the 5.2L engine spark plugs to 41 N⅐m (30 ft. amount and grade of oil (refer to Group 0, Lubrica-lbs.) torque. tion and Maintenance). (11) Drain engine oil. Remove and discard the oil (15) Connect the negative cable to the battery.filter. (16) Start the engine and check for any leaks. (12) Install the drain plug. Tighten the drain plugto 34 N⅐m (25 ft. lbs.) torque.
  6. 6. 9-6 ENGINES ZJ ENGINE DIAGNOSIS Engine diagnosis is helpful in determining the (5) Insert a compression pressure gauge and rotatecauses of malfunctions not detected and remedied by the engine with the engine starter motor for threeroutine tune-ups. revolutions. These malfunctions may be classified as either per- (6) Record the compression pressure on the 3rdformance (engine idles rough and stalls) or mechani- revolution. Continue the test for the remaining cylin-cal (a strange noise). ders. Refer to the Service Diagnosis—Performance chart Refer to Engine Specifications for the correct en-and the Service Diagnosis—Mechanical chart for pos- gine compression pressures.sible causes and corrections of malfunctions. Refer toGroup 14, Fuel System for the fuel system diagnosis. ENGINE CYLINDER HEAD GASKET FAILURE DIAGNOSISGENERAL INFORMATION A leaking engine cylinder head gasket usually re- Additional tests and diagnostic procedures may be sults in loss of power, loss of coolant and engine mis-necessary for specific engine malfunctions that can firing.not be isolated with the Service Diagnosis charts. In- An engine cylinder head gasket leak can be locatedformation concerning additional tests and diagnosis between adjacent cylinders or between a cylinder andis provided within the following diagnosis: the adjacent water jacket.• Cylinder Compression Pressure Test. • An engine cylinder head gasket leaking between• Cylinder Combustion Pressure Leakage Test. adjacent cylinders is indicated by a loss of power or• Engine Cylinder Head Gasket Failure Diagnosis. engine misfire.• Intake Manifold Leakage Diagnosis. • An engine cylinder head gasket leaking between a cylinder and an adjacent water jacket is indicated byINTAKE MANIFOLD LEAKAGE DIAGNOSIS coolant foaming or overheating and loss of coolant. An intake manifold air leak is characterized bylower than normal manifold vacuum. Also, one or CYLINDER-TO-CYLINDER LEAKAGE TESTmore cylinders may not be functioning. To determine if an engine cylinder head gasket is leaking between adjacent cylinders; follow the proce-WARNING: USE EXTREME CAUTION WHEN THE dures outlined in Cylinder Compression PressureENGINE IS OPERATING. DO NOT STAND IN A DI- Test. An engine cylinder head gasket leaking betweenRECT LINE WITH THE FAN. DO NOT PUT YOUR adjacent cylinders will result in approximately a 50-HANDS NEAR THE PULLEYS, BELTS OR THE FAN. 70% reduction in compression pressure.DO NOT WEAR LOOSE CLOTHING. CYLINDER-TO-WATER JACKET LEAKAGE (1) Start the engine. TEST (2) Spray a small stream of water at the suspectedleak area. WARNING: USE EXTREME CAUTION WHEN THE (3) If a change in RPM’S, the area of the suspected ENGINE IS OPERATING. DO NOT STAND IN A DI-leak has been found. RECT LINE WITH THE FAN. DO NOT PUT YOUR (4) Repair as required. HANDS NEAR THE PULLEYS, BELTS OR THE FAN. DO NOT WEAR LOOSE CLOTHING.CYLINDER COMPRESSION PRESSURE TEST The results of a cylinder compression pressure test Remove the radiator cap.can be utilized to diagnose several engine malfunc- Start the engine and allow it to warm up until thetions. engine thermostat opens. Ensure the battery is completely charged and the If a large combustion/compression pressure leak ex-engine starter motor is in good operating condition. ists, bubbles will be visible in the coolant.Otherwise the indicated compression pressures may If bubbles are not visible, install a radiator pres-not be valid for diagnosis purposes. sure tester and pressurize the coolant system. (1) Clean the spark plug recesses with compressed If a cylinder is leaking combustion pressure intoair. the water jacket, the tester pointer will pulsate with (2) Remove the spark plugs. every combustion stroke of the cylinder. (3) Secure the throttle in the wide-open position. (4) Disconnect the ignition coil.
  7. 7. ZJ ENGINES 9-7CYLINDER COMBUSTION PRESSURE LEAKAGE (3) Using a black light, inspect the entire engineTEST for fluorescent dye, particularly at the suspected area The combustion pressure leakage test provides an of oil leak. If the oil leak is found and identified, re-accurate means for determining engine condition. pair per service manual instructions. Combustion pressure leakage testing will detect: (4) If dye is not observed, drive the vehicle at var-• Exhaust and intake valve leaks (improper seat- ious speeds for approximately 24km (15 miles), anding). repeat step (3).• Leaks between adjacent cylinders or into water If the oil leak source is not positively identi-jacket. fied at this time, proceed with the air leak detec-• Any causes for combustion/compression pressure tion test method as follows:loss. (1) Disconnect the breather cap to air cleaner hose at the breather cap end. Cap or plug breather capWARNING: DO NOT REMOVE THE RADIATOR CAP nipple.WITH THE SYSTEM HOT AND UNDER PRESSURE (2) Remove the PCV valve from the cylinder headBECAUSE SERIOUS BURNS FROM COOLANT CAN cover. Cap or plug the PCV valve grommet.OCCUR. (3) Attach an air hose with pressure gauge and regulator to the dipstick tube. Check the coolant level and fill as required. DO CAUTION: Do not subject the engine assembly toNOT install the radiator cap. more than 20.6 kpa (3 PSI) of test pressure. Start and operate the engine until it attains nor-mal operating temperature, then turn the engine (4) Gradually apply air pressure from 1 psi to 2.5OFF. psi maximum while applying soapy water at the sus- Remove the spark plugs. pected source. Adjust the regulator to the suitable Remove the oil filler cap. test pressure that provide the best bubbles which Remove the air cleaner. will pinpoint the leak source. If the oil leak is de- Calibrate the tester according to the manufactur- tected and identified, repair per service manual pro-er’s instructions. The shop air source for testing cedures.should maintain 483 kPa (70 psi) minimum, 1 379 (5) If the leakage occurs at the rear oil seal area,kPa (200 psi) maximum and 552 kPa (80 psi) recom- refer to the section, Inspection for Rear Seal Areamended. Leak. Perform the test procedures on each cylinder ac- (6) If no leaks are detected, turn off the air supplycording to the tester manufacturer’s instructions. and remove the air hose and all plugs and caps. In-While testing, listen for pressurized air escaping stall the PCV valve and breather cap hose. Proceedthrough the throttle body, tailpipe and oil filler cap to step 7.opening. Check for bubbles in the radiator coolant. (7) Clean the oil off the suspect oil leak area using All gauge pressure indications should be equal, a suitable solvent. Drive the vehicle at variouswith no more than 25% leakage. speeds approximately 24 km (15 miles). Inspect the engine for signs of an oil leak by using a black light. FOR EXAMPLE: At 552 kPa (80 psi) input pres-sure, a minimum of 414 kPa (60 psi) should be main- INSPECTION FOR REAR SEAL AREA LEAKStained in the cylinder. Since it is sometimes difficult to determine the Refer to the Cylinder Combustion Pressure Leak- source of an oil leak in the rear seal area of the en-age Test Diagnosis chart. gine, a more involved inspection is necessary. The fol- lowing steps should be followed to help pinpoint theINSPECTION (ENGINE OIL LEAKS IN GENERAL) source of the leak. Begin with a through visual inspection of the en- If the leakage occurs at the crankshaft rear oil sealgine, particularly at the area of the suspected leak. If area:an oil leak source is not readily identifiable, the fol- (1) Disconnect the battery.lowing steps should be followed: (2) Raise the vehicle. (1) Do not clean or degrease the engine at this (3) Remove torque converter or clutch housingtime because some solvents may cause rubber to cover and inspect rear of block for evidence of oil.swell, temporarily stopping the leak. Use a black light to check for the oil leak: (2) Add an oil soluble dye (use as recommended by (a) Circular spray pattern generally indicatesmanufacturer). Start the engine and let idle for ap- seal leakage or crankshaft damage.proximately 15 minutes. Check the oil dipstick to (b) Where leakage tends to run straight down,make sure the dye is thoroughly mixed as indicated possible causes are a porous block, distributor seal,with a bright yellow color under a black light. camshaft bore cup plugs oil galley pipe plugs, oil
  8. 8. 9-8 ENGINES ZJ filter runoff, and main bearing cap to cylinder (6) For bubbles that remain steady with shaft ro- block mating surfaces. See Group 9, Engines for tation, no further inspection can be done until disas- proper repair procedures of these items. sembled. Refer to the service Diagnosis—Mechanical, (4) If no leaks are detected, pressurized the crank- under the Oil Leak row for components inspectionscase as outlined in the, Inspection (Engine oil Leaks on possible causes and corrections.in general) (7) After the oil leak root cause and appropriate corrective action have been identified, Refer to GroupCAUTION: Do not exceed 20.6 kPa (3 psi). 9, Engines—Crankshaft Rear Oil Seals, for proper re- (5) If the leak is not detected, very slowly turn the placement procedures.crankshaft and watch for leakage. If a leak is de-tected between the crankshaft and seal while slowly ENGINE OIL PRESSUREturning the crankshaft, it is possible the crankshaft (1) Remove oil pressure sending unit.seal surface is damaged. The seal area on the crank- (2) Install Oil Pressure Line and Gauge Toolshaft could have minor nicks or scratches that can be C-3292. Start engine and record pressure. Refer topolished out with emery cloth. Oil Pressure in Engine Specifications for the proper pressures.CAUTION: Use extreme caution when crankshaftpolishing is necessary to remove minor nicks andscratches. The crankshaft seal flange is especiallymachined to complement the function of the rear oilseal.
  9. 9. ZJ ENGINES 9-9 SERVICE DIAGNOSIS—PERFORMANCE
  10. 10. 9 - 10 ENGINES ZJ SERVICE DIAGNOSIS—MECHANICAL
  11. 11. ZJ ENGINES 9 - 11 SERVICE DIAGNOSIS—LUBRICATION
  12. 12. 9 - 12 4.0L ENGINE ZJ 4.0L ENGINE SERVICE PROCEDURES INDEX page pageCamshaft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Rocker Arms and Push Rods . . . . . . . . . .... . . . 18Camshaft Pin Replacement . . . . . . . . . . . . . . . . . . 29 Timing Case Cover . . . . . . . . . . . . . . . . . .... . . . 25Engine Assembly . . . . . . . . . . . . . . . . . . . . . . . . . 14 Timing Case Cover Oil Seal Replacement .... . . . 26Engine Cylinder Head . . . . . . . . . . . . . . . . . . . . . . 20 Timing Chain and Sprockets . . . . . . . . . . .... . . . 26Engine Cylinder Head Cover . . . . . . . . . . . . . . . . . 17 Valve Component Replace—Cylinder Head NotEngine Mount—Rear . . . . . . . . . . . . . . . . . . . . . . . 14 Removed . . . . . . . . . . . . . . . . . . . . . . . .... . . . 18Engine Mounts—Front . . . . . . . . . . . . . . . . . . . . . 13 Valve Stem Seal and Spring Replacement .... . . . 18General Information . . . . . . . . . . . . . . . . . . . . . . . 12 Valve Timing . . . . . . . . . . . . . . . . . . . . . . .... . . . 24Hydraulic Tappets . . . . . . . . . . . . . . . . . . . . . . . . . 19 Valves and Valve Springs . . . . . . . . . . . . .... . . . 22Oil Pan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Vibration Damper . . . . . . . . . . . . . . . . . . .... . . . 25GENERAL INFORMATION The 4.0 Liter (242 CID) six-cylinder engine is anIn-line, lightweight, overhead valve engine (Fig. 1). Fig. 2 Engine Firing Order BUILD DATE CODE The engine Build Date Code is located on a ma- chined surface on the right side of the cylinder block between the No.2 and No.3 cylinders (Fig. 3). Fig. 1 Engine Description This engine is designed for unleaded fuel. The engine cylinder head has dual quench-typecombustion chambers that create turbulence and fastburning of the air/fuel mixture. This results in goodfuel economy. The cylinders are numbered 1 through 6 from frontto rear. The firing order is 1-5-3-6-2-4 (Fig. 2). The crankshaft rotation is clockwise, when viewedfrom the front of the engine. The crankshaft rotateswithin seven main bearings. The camshaft rotateswithin four bearings. Fig. 3 Build Date Code Location The digits of the code identify:
  13. 13. ZJ 4.0L ENGINE 9 - 13 (1) 1st Digit—The year (4 = 1994). (2) 2nd & 3rd Digits—The month (01 - 12). (3) 4th & 5th Digits—The engine type/fuel system/compression ratio (MX = A 4.0 Liter (242 CID) 8.8:1compression ratio engine with a multi-point fuel in-jection system). (4) 6th & 7th Digits—The day of engine build (01 -31). FOR EXAMPLE: Code * 401MX12 * Identifies a4.0 Liter (242 CID) engine with a multi-point fuel in-jection system, 8.7:1 compression ratio and built onJanuary 12, 1994.OVERSIZE AND UNDERSIZE COMPONENTCODES Some engines may be built with oversize or under-size components such as:• Oversize cylinder bores.• Oversize camshaft bearing bores.• Undersize crankshaft main bearing journals.• Undersize connecting rod journals. These engines are identified by a letter code (Fig. Fig. 5 Oversize and Undersize Component Code4) stamped on a boss between the ignition coil and Locationthe distributor (Fig. 5). REMOVAL (1) Disconnect the negative cable from the battery. (2) Support the engine. (3) Raise the vehicle. (4) Remove the insulator assembly-to-lower front sill bolts (Fig. 6 or 7). (5) Raise the engine slightly. (6) Remove the thru-bolt nut and thru-bolt (Fig. 6 or 7). Remove the insulator. Fig. 4 Oversize and Undersize Component CodesENGINE MOUNTS—FRONT The front mounts support the engine at each side. Fig. 6 Front Engine Mount—Right SideThese insulators are made of resilient rubber.
  14. 14. 9 - 14 4.0L ENGINE ZJ Fig. 8 Engine Mount—Rear Fig. 7 Front Engine Mount—Left Side (6) Remove the bolts holding the rear mount (7) If required, remove the engine bracket from the bracket to the transmission (Fig. 8). Remove theblock (Fig. 6 or 7). bracket from the exhaust pipe hanger. Remove theINSTALLATION bracket. (1) If removed, install the engine bracket to the INSTALLATIONblock (Fig. 6 or 7). Tighten the bolts to 61 N⅐m (45 ft. (1) Position the rear mount bracket onto the ex-lbs.) torque. haust hanger. Position the rear mount bracket as- (2) Install the insulator assembly to the lower sembly onto the transmission and install the boltsfront sill. Tighten the bolts to 65 N⅐m (48 ft. lbs.) (Fig. 8). Tighten the bolts to the proper torque:torque. • MANUAL TRANSMISSION—Tighten to 46 N⅐m (3) With the engine insulator assembly and engine (34 ft. lbs.) torque.bracket in position, install the thru-bolt and nut (Fig. • AUTOMATIC TRANSMISSION—Tighten to 756 or 7). Tighten the thru-bolt nut to 121 N⅐m (89 ft. N⅐m (55 ft. lbs.) torque.lbs.) torque. (2) Install the thru-bolt into the rear mount (4) Lower the vehicle. bracket and clevis (Fig. 8). Finger tighten the nut at (5) Remove the engine support. this time. (6) Connect the negative cable to the battery. (3) Lower the transmission until the clevis bracket studs are in position on the crossmember (Fig. 8). In-ENGINE MOUNT—REAR stall the clevis bracket stud nuts. Tighten the nuts to A resilient rubber cushion bracket assembly sup- 41 N⅐m (30 ft. lbs) torque.ports the transmission at the rear. This bracket is at- (4) Tighten the thru-bolt nut to 121 N⅐m (89 ft.tached to the crossmember (Fig. 8). lbs.) torque.REMOVAL (5) Remove the transmission support. (1) Disconnect the negative cable from the battery. (6) Lower the vehicle. (2) Raise the vehicle and support the transmission. (7) Connect the negative cable to the battery. (3) Remove the nuts holding the clevis bracket tothe crossmember (Fig. 8). ENGINE ASSEMBLY (4) Raise the transmission SLIGHTLY. REMOVAL (5) Remove the thru-bolt and nut (Fig. 8). Remove (1) Disconnect the battery cables. Remove the bat-the rear mount bracket clevis. tery.
  15. 15. ZJ 4.0L ENGINE 9 - 15 (2) Mark the hinge locations on the hood panel for (14) Disconnect the vehicle speed control cable (ifalignment reference during installation. Remove the equipped)—(Fig. 10).engine compartment lamp. Remove the hood. (15) Disconnect the line pressure cable (if equipped with automatic transmission).WARNING: THE COOLANT IN A RECENTLY OPER- (16) Disconnect injection system wire harness con-ATED ENGINE IS HOT AND PRESSURIZED. USE nector at each injector. Mark the wires for proper in-CARE TO PREVENT SCALDING BY HOT COOLANT. stallation.CAREFULLY RELEASE THE PRESSURE BEFORE (17) Disconnect the distributor electrical connec-REMOVING THE RADIATOR DRAIN COCK AND CAP. tion and the oil pressure switch connector. (3) Remove the radiator drain cock and radiator (18) Disconnect the quick-connect fuel lines at thecap to drain the coolant. DO NOT waste usable cool- fuel rail and return line by squeezing the two retain-ant. If the solution is clean, drain the coolant into a ing tabs against the fuel tube (Fig. 10). Pull the fuelclean container for reuse. tube and retainer from the quick-connect fitting (re- (4) Remove the upper radiator hose and coolant re- fer to Group 14, Fuel System for the proper proce-covery hose (Fig. 9). dure). (5) Remove the lower radiator hose. (6) Remove upper radiator support retaining boltsand remove radiator support. (7) Remove the fan assembly from the water pump. (8) Remove the fan shroud (Fig. 9). (9) Disconnect the transmission fluid cooler tubing(automatic transmission). (10) Vehicles with Air Conditioning: (a) Discharge the A/C system (refer to Group 24, Heating and Air Conditioning). (b) Remove the service valves and cap the com- pressor ports. (11) Remove the radiator or radiator/condenser (ifequipped with A/C). (12) Disconnect the heater hoses at the enginethermostat housing and water pump (Fig. 9). Fig. 10 Accelerator Cable, Vehicle Speed Control Cable, Automatic Transmission Control Cable & Quick-Connect Fuel Lines (19) Remove the fuel line bracket from the intake manifold. (20) Remove the air cleaner assembly (Fig. 11). (21) Remove the power brake vacuum check valve from the booster, if equipped. (22) Vehicles with Power Steering (Fig. 11): (a) Disconnect the hoses from the fittings at the steering gear. (b) Drain the pump reservoir. (c) Cap the fittings on the hoses and steering gear to prevent foreign objects from entering the system. (23) Identify, tag and disconnect all necessary wire connectors and vacuum hoses. Fig. 9 Upper Radiator Hose, Coolant Recovery (24) Raise and support the vehicle. Hose, Fan Shroud & Heater hoses (25) Disconnect the wires from the engine starter (13) Disconnect the throttle linkages (Fig. 10). motor solenoid.
  16. 16. 9 - 16 4.0L ENGINE ZJ (1) Attach a lifting device to the engine and lower the engine into the engine compartment. For easier installation, it may be necessary to remove the en- gine mount bracket as an aid in alignment of the en- gine to the transmission. (2) Vehicles with Manual Transmission: (a) Insert the transmission shaft into the clutch spline. (b) Align the engine flywheel housing with the engine. (c) Install and tighten the engine flywheel hous- ing lower bolts finger tight. (3) Vehicles with Automatic Transmission: (a) Align the transmission torque converter hous- ing with the engine. (b) Loosely install the converter housing lower bolts and install the next higher bolt and nut on each side. (c) Tighten all 4 bolts finger tight. (4) Install the engine mount brackets (if removed). (5) Lower the engine and engine mount brackets Fig. 11 Air Cleaner Assembly & Power Steering onto the engine compartment cushions. Install the Pump bolts and finger tighten the nuts. (26) Remove the engine starter motor. (6) Remove the engine lifting device. (27) Disconnect the oxygen sensor from the ex- (7) Raise and support the vehicle.haust pipe. (8) Install the remaining engine flywheel/converter (28) Disconnect the exhaust pipe from the mani- housing bolts. Tighten all bolts to 38 N⅐m (28 ft. lbs.)fold. torque. (29) Disconnect the vehicle speed sensor wire con- (9) Vehicles with Automatic Transmission:nection. (a) Install the converter-to-drive plate bolts. (30) Remove the exhaust pipe support. (b) Ensure the installation reference marks are (31) Remove the engine flywheel/converter housing aligned.access cover. (10) Install the engine flywheel/converter housing (32) Vehicles with Automatic Transmission: access cover. (a) Mark the converter and drive plate location. (11) Install the exhaust pipe support and tighten (b) Remove the converter-to-drive plate bolts. the screw. (33) Remove the upper engine flywheel/converter (12) Tighten the engine mount-to-bracket bolts.housing bolts and loosen the bottom bolts. (13) Connect the vehicle speed sensor wire connec- (34) Remove the engine mount cushion-to-engine tions and tighten the screws.compartment bracket bolts. (14) Connect the exhaust pipe to the manifold. (35) Lower the vehicle. (15) Install the engine starter motor and connect (36) Attach a lifting device to the engine. the cable. (37) Raise the engine off the front supports. (16) Connect the wires to the engine starter motor (38) Place a support or floor jack under the con- solenoid.verter (or engine flywheel) housing. (17) Lower the vehicle. (39) Remove the remaining converter (or engine (18) Connect all the vacuum hoses and wire con-flywheel) housing bolts. nectors identified during engine removal. (40) Lift the engine out of the engine compart- (19) Vehicles equipped with Power Steering:ment. (a) Remove the protective caps (b) Connect the hoses to the fittings at the steer-INSTALLATION ing gear. Tighten the nut to 52 N⅐m (38 ft. lbs.) torque.CAUTION: When installing the engine into a vehicle (c) Fill the pump reservoir with fluid.equipped with an automatic transmission, be care- (20) Install the power brake vacuum check valveful not to damage the trigger wheel on the engine from the booster, if equipped.flywheel.
  17. 17. ZJ 4.0L ENGINE 9 - 17 (21) Connect the fuel inlet and return hoses at the ENGINE CYLINDER HEAD COVERfuel rail. Verify that the quick-connect fitting assem- A cured gasket is part of the engine cylinder headbly fits securely over the fuel lines by giving the fuel cover.lines a firm tug. (22) Install the fuel line bracket to the intake man- REMOVALifold. (1) Disconnect negative cable from battery. (23) Connect the distributor electrical connector (2) Disconnect the Crankcase Ventilation (CCV)and oil pressure switch connector. vacuum hose from engine cylinder head cover (Fig. (24) Connect the injection system wires to the in- 1).jectors. (3) Disconnect the fresh air inlet hose from the en- gine cylinder head cover (Fig. 1). (25) Connect the line pressure cable (if equipped (4) Remove the engine cylinder head cover mount-with automatic transmission). ing bolts. (26) Connect the vehicle speed control cable, if (5) Remove the engine cylinder head cover.equipped. (27) Connect the throttle cable linkages. (28) Connect the heater hoses at the engine ther-mostat housing and water pump. (29) Install the fan assembly to the water pump. (30) Place the fan shroud in position over the fan. (31) Install the radiator or radiator/condenser (ifequipped with A/C). (32) Connect the service valves to the A/C compres-sor ports, if equipped with A/C. (33) Charge the air conditioner system (refer toGroup 24, Heating and Air Conditioning). (34) Connect the radiator hoses and automatictransmission fluid cooler pipes, if equipped. (35) Install the fan shroud to the radiator or radi-ator/condenser (if equipped with A/C). (36) Install upper radiator support. (37) Connect the upper radiator hose and tighten Fig. 1 Engine Cylinder Head Coverthe clamp. CLEANING (38) Connect the lower radiator hose and tighten Remove any original sealer from the cover sealingthe clamp. surface of the engine cylinder head and clean the (39) Fill the cooling system with reusable coolant surface using a fabric cleaner.or new coolant (refer to Group 7, Cooling System). Remove all residue from the sealing surface using (40) Align the hood to the scribe marks. Install the a clean, dry cloth.hood. INSPECTION (41) Connect the vacuum harness connector. Inspect the engine cylinder head cover for cracks. (a) Firmly push the connectors together ensuring Replace the cover, if cracked. that the retaining tabs are engaged. The original dark grey gasket material should NOT (b) Insert the vacuum connector assembly into be removed. If sections of the gasket material are the retaining bracket on the intake manifold. missing or are compressed, replace the engine cylin- (42) Install the air cleaner assembly. der head cover. However, sections with minor damage (43) Install the battery and connect the battery ca- such as small cracks, cuts or chips may be repairedble. with a hand held applicator. The new material must be smoothed over to maintain gasket height. AllowWARNING: USE EXTREME CAUTION WHEN THE the gasket material to cure prior to engine cylinderENGINE IS OPERATING. DO NOT STAND IN A DI- head cover installation.RECT LINE WITH THE FAN. DO NOT PUT YOURHANDS NEAR THE PULLEYS, BELTS OR FAN. DO INSTALLATIONNOT WEAR LOOSE CLOTHING. (1) If a replacement cover is installed, transfer the CCV valve grommet and oil filler cap from the origi- (44) Start the engine, inspect for leaks and correct nal cover to the replacement cover.the fluid levels, as necessary. (2) Install engine cylinder head cover. Tighten the mounting bolts to 10 N⅐m (85 in. lbs.) torque.
  18. 18. 9 - 18 4.0L ENGINE ZJ (3) Connect the CCV hoses (Fig. 1). Inspect each push rod end for excessive wear and (4) Connect negative cable to battery. replace as required. If any push rod is excessively worn because of lack of oil, replace it and inspect theVALVE COMPONENT REPLACE—CYLINDER HEAD corresponding hydraulic tappet for excessive wear.NOT REMOVED Inspect the push rods for straightness by rolling them on a flat surface or by shining a light betweenROCKER ARMS AND PUSH RODS the push rod and the flat surface. This procedure can be done with the engine in or A wear pattern along the length of the push rod isout of the vehicle. not normal. Inspect the engine cylinder head for ob- struction if this condition exists.REMOVAL (1) Remove the engine cylinder head cover. INSTALLATION (2) Remove the capscrews at each bridge and pivot (1) Lubricate the ball ends of the push rods withassembly (Fig. 2). Alternately loosen the capscrews Mopar௡ Engine Oil Supplement, or equivalent and install push rods in their original locations. Ensureone turn at a time to avoid damaging the bridges. that the bottom end of each push rod is centered in (3) Check for rocker arm bridges which are causing the tappet plunger cap seat.misalignment of the rocker arm to valve tip area. (2) Using Mopar௡ Engine Oil Supplement, or (4) Remove the bridges, pivots and corresponding equivalent, lubricate the area of the rocker arm thatpairs of rocker arms (Fig. 2). Place them on a bench the pivot contacts. Install rocker arms, pivots andin the same order as removed. bridge above each cylinder in their original position. (5) Remove the push rods and place them on a (3) Loosely install the capscrews through eachbench in the same order as removed. bridge. (4) At each bridge, tighten the capscrews alter- nately, one turn at a time, to avoid damaging the bridge. Tighten the capscrews to 28 N⅐m (21 ft. lbs.) torque. (5) Install the engine cylinder head cover. VALVE STEM SEAL AND SPRING REPLACEMENT This procedure can be done with the engine cylin- der head installed on the block. REMOVAL Each valve spring is held in place by a retainer and a set of conical valve locks. The locks can be removed only by compressing the valve spring. (1) Remove the engine cylinder head cover. (2) Remove capscrews, bridge and pivot assemblies and rocker arms for access to each valve spring to be removed. (3) Remove push rods. Retain the push rods, bridges, pivots and rocker arms in the same order and position as removed. (4) Inspect the springs and retainer for cracks and Fig. 2 Rocker Arm Assembly possible signs of weakening.CLEANING (5) Remove the spark plug(s) adjacent to the cylin- Clean all the components with cleaning solvent. der(s) below the valve springs to be removed. Use compressed air to blow out the oil passages in (6) Install a 14 mm (1/2 inch) (thread size) air hosethe rocker arms and push rods. adaptor in the spark plug hole. An adaptor can be constructed by welding an air hose connection to theINSPECTION body of a spark plug with the porcelain removed. Inspect the pivot surface area of each rocker arm. (7) Connect an air hose to the adapter and applyReplace any that are scuffed, pitted, cracked or ex- air pressure slowly. Maintain at least 621 kPa (90cessively worn. psi) of air pressure in the cylinder to hold the valves Inspect the valve stem tip contact surface of each against their seats. For vehicles equipped with an airrocker arm and replace any rocker arm that is deeply conditioner, use a flexible air adaptor when servicingpitted. the No.1 cylinder.
  19. 19. ZJ 4.0L ENGINE 9 - 19 (8) Tap the retainer or tip with a rawhide hammer (6) Install the push rods. Ensure the bottom end ofto loosen the lock from the retainer. Use Valve Spring each rod is centered in the plunger cap seat of theCompressor Tool MD-998772A to compress the spring hydraulic valve tappet.and remove the locks (Fig. 3). (7) Install the rocker arms, pivots and bridge at (9) Remove valve spring and retainer (Fig. 3). their original location. (10) Remove valve stem oil seals (Fig. 3). Note the (8) Tighten the bridge capscrews alternately, onevalve seals are different for intake and exhaust at a time, to avoid damaging the bridge. Tighten thevalves. The top of each seal is marked either INT (In- capscrews to 28 N⅐m (21 ft. lbs.) torque.take) or EXH (Exhaust). DO NOT mix the seals. (9) Install the engine cylinder head cover. HYDRAULIC TAPPETS Retain all the components in the same order as re- moved. REMOVAL (1) Remove the engine cylinder head cover. (2) Remove the bridge and pivot assemblies and rocker arms by removing the capscrews at each bridge. Alternately loosen each capscrew, one turn at a time, to avoid damaging the bridges. (3) Remove the push rods. (4) Remove the intake and engine exhaust mani- folds (refer to Group 11, Exhaust System and Intake Manifold for the proper procedure). (5) Remove the engine cylinder head and gasket. (6) Remove the tappets through the push rod open- ings in the cylinder block with Hydraulic Valve Tap- pet Removal/Installation Tool C-4129-A (Fig. 4). Fig. 3 Valve and Valve ComponentsINSPECTION Inspect the valve stems, especially the grooves. AnArkansas smooth stone should be used to removenicks and high spots.INSTALLATIONCAUTION: Install oil seals carefully to prevent dam-age from the sharp edges of the valve spring lockgrove. (1) Lightly push the valve seal over the valve stemand valve guide boss. Be sure the seal is completelyseated on the valve guide boss. (2) Install valve spring and retainer. (3) Compress the valve spring with Valve SpringCompressor Tool MD-988772A and insert the valvelocks. Release the spring tension and remove thetool. Tap the spring from side-to-side to ensure that Fig. 4 Hydraulic Valve Tappet Removal/Installationthe spring is seated properly on the engine cylinder Tool C-4129-Ahead. CLEANING (4) Disconnect the air hose. Remove the adaptor Clean each tappet assembly in cleaning solvent tofrom the spark plug hole and install the spark plug. remove all varnish, gum and sludge deposits. (5) Repeat the procedures for each remaining valvespring to be removed.
  20. 20. 9 - 20 4.0L ENGINE ZJINSPECTION Inspect for indications of scuffing on the side andbase of each tappet body. Inspect each tappet base for concave wear with astraightedge positioned across the base. If the base isconcave, the corresponding lobe on the camshaft isalso worn. Replace the camshaft and defective tap-pets.LEAK-DOWN TEST After cleaning and inspection, test each tappet forspecified leak-down rate tolerance to ensure zero-lashoperation (Fig. 5). Swing the weighted arm of the hydraulic valve tap-pet tester away from the ram of the Leak-DownTester 7980. (1) Place a 7.925-7.950 mm (0.312-0.313 inch) di- Fig. 5 Leak-Down Tester 7980ameter ball bearing on the plunger cap of the tappet. (2) Lift the ram and position the tappet (with the (5) Install the push rods in their original locations.ball bearing) inside the tester cup. (6) Install the rocker arms and bridge and pivot (3) Lower the ram, then adjust the nose of the ram assemblies at their original locations. Loosely installuntil it contacts the ball bearing. DO NOT tighten the capscrews at each bridge.the hex nut on the ram. (7) Tighten the capscrews alternately, one turn at (4) Fill the tester cup with hydraulic valve tappet a time, to avoid damaging the bridges. Tighten thetest oil until the tappet is completely submerged. capscrews to 28 N⅐m (21 ft. lbs.) torque. (5) Swing the weighted arm onto the push rod and (8) Pour the remaining Mopar௡ Engine Oil Supple-pump the tappet plunger up and down to remove air. ment, or equivalent over the entire valve actuatingWhen the air bubbles cease, swing the weighted arm assembly. The Mopar௡ Engine Oil Supplement, oraway and allow the plunger to rise to the normal po- equivalent must remain with the engine oil for atsition. least 1 609 km (1,000 miles). The oil supplement (6) Adjust the nose of the ram to align the pointer need not be drained until the next scheduled oilwith the SET mark on the scale of the tester and change.tighten the hex nut. (9) Install the engine cylinder head cover. (7) Slowly swing the weighted arm onto the pushrod. ENGINE CYLINDER HEAD (8) Rotate the cup by turning the handle at the This procedure can be done with the engine in orbase of the tester clockwise one revolution every 2 out of the vehicle.seconds. (9) Observe the leak-down time interval from the REMOVALinstant the pointer aligns with the START mark on (1) Disconnect negative cable from battery.the scale until the pointer aligns with the 0.125mark. A normally functioning tappet will require 20- WARNING: DO NOT REMOVE THE CYLINDER110 seconds to leak-down. Discard tappets with leak- BLOCK DRAIN PLUGS OR LOOSEN THE RADIATORdown time interval not within this specification. DRAIN COCK WITH THE SYSTEM HOT AND PRES- SURIZED BECAUSE SERIOUS BURNS FROM THEINSTALLATION COOLANT CAN OCCUR. It is not necessary to charge the tappets with en-gine oil. They will charge themselves within a very (2) Drain the coolant and disconnect the hoses atshort period of engine operation. the engine thermostat housing. DO NOT waste reus- (1) Dip each tappet in Mopar௡ Engine Oil Supple- able coolant. If the solution is clean and is beingment, or equivalent. drained only to service the engine or cooling system, (2) Use Hydraulic Valve Tappet Removal/Installa- drain the coolant into a clean container for reuse.tion Tool C-4129-A to install each tappet in the same (3) Remove the air cleaner assembly.bore from where it was originally removed. (4) Remove the engine cylinder head cover. (3) Install the exhaust and intake manifolds (referto Group 11, Exhaust System and Intake Manifold (5) Remove the capscrews, bridge and pivot assem-for the proper procedure). blies and rocker arms (Fig. 2). (4) Install the engine cylinder head and gasket.
  21. 21. ZJ 4.0L ENGINE 9 - 21 (6) Remove the push rods (Fig. 2). Retain thepush rods, bridges, pivots and rocker arms inthe same order as removed. (7) Loosen the serpentine drive belt at the powersteering pump, if equipped or at the idler pulley (re-fer to Group 7, Cooling System for the proper proce-dure). (8) If equipped with air conditioning, perform thefollowing: (a) Remove the bolts from the A/C compressor mounting bracket and set the compressor aside. (b) Remove the air conditioner compressor bracket bolts from the engine cylinder head. (c) Loosen the thru-bolt at the bottom of the bracket. (9) If equipped, disconnect the power steeringpump bracket. Set the pump and bracket aside. DO Fig. 6 Engine Cylinder Head AssemblyNOT disconnect the hoses. INSPECTION (10) Perform the Fuel System Pressure Release Use a straightedge and feeler gauge to check theprocedure (refer to Group 14, Fuel System). Remove flatness of the engine cylinder head and block matingthe fuel lines and vacuum advance hose. surfaces. (11) Remove the intake and engine exhaust mani-folds from the engine cylinder head (refer to Group INSTALLATION11, Exhaust System and Intake Manifold for the The engine cylinder head gasket is a compositionproper procedures). gasket. The gasket is to be installed DRY. DO NOT (12) Disconnect the ignition wires and remove the use a gasket sealing compound on the gasket.spark plugs. If the engine cylinder head is to be replaced and (13) Disconnect the temperature sending unit wire the original valves used, measure the valve stem di-connector. ameter. Only standard size valves can be used with a (14) Remove the ignition coil and bracket assem- service replacement engine cylinder head unless thebly. replacement head valve stem guide bores are reamed (15) Remove the engine cylinder head bolts. Bolt to accommodate oversize valve stems. Remove allNo.14 cannot be removed until the head is moved for- carbon buildup and reface the valves.ward. Pull bolt No.14 out as far as it will go and then (1) Remove the shop towels from the cylindersuspend the bolt in this position (tape around the bores. Coat the bores with clean engine oil.bolt). (2) Position the engine cylinder head gasket (with (16) Remove the engine cylinder head and gasket the numbers facing up) onto the cylinder block.(Fig. 6). CAUTION: Engine cylinder head bolts should be re- (17) If this was the first time the bolts were re- used only once. Replace the head bolts if they weremoved, put a paint dab on the top of the bolt. If the used before or if they have a paint dab on the topbolts have a paint dab on the top of the bolt or it of the bolt.isn’t known if they were used before, discard thebolts. (3) With bolt No.14 held in place (tape around (18) Stuff clean lint free shop towels into the cylin- bolt), install the engine cylinder head. Remove theder bores. tape from bolt No.14. (4) Coat the threads of stud bolt No.11 with LoctiteCLEANING 592 sealant, or equivalent. Thoroughly clean the engine cylinder head and cyl- (5) Tighten the engine cylinder head bolts in se-inder block mating surfaces. Clean the intake and quence according to the following procedure (Fig. 7):engine exhaust manifold and engine cylinder head (a) Tighten all bolts in sequence (1 through 14)mating surfaces. Remove all gasket material and car- to 30 N⅐m (22 ft. lbs.) torque.bon. (b) Tighten all bolts in sequence (1 through 14) Check to ensure that no coolant or foreign material to 61 N⅐m (45 ft. lbs.) torque.has fallen into the tappet bore area. (c) Check all bolts to verify they are set to 61 Remove the carbon deposits from the combustion N⅐m (45 ft. lbs.) torque.chambers and top of the pistons. (d) Tighten bolts (in sequence):
  22. 22. 9 - 22 4.0L ENGINE ZJ• Bolts 1 through 10 to 149 N⅐m (110 ft. lbs.) torque. (16) Install the serpentine drive belt and correctly• Bolt 11 to 136 N⅐m (100 ft. lbs.) torque. tension the belt (refer to Group 7, Cooling System for• Bolts 12 through 14 to 149 N⅐m (110 ft. lbs.) the proper procedure).torque. (17) Install the air cleaner and ducting. (18) Install the engine cylinder head cover.CAUTION: During the final tightening sequence, (19) Connect the hoses to the engine thermostatbolt No.11 will be tightened to a lower torque than housing and fill the cooling system to the specifiedthe rest of the bolts. DO NOT overtighten bolt level (refer to Group 7, Cooling Systems for theNo.11. proper procedure). (20) The automatic transmission throttle linkage (e) Check all bolts in sequence to verify the cor- and cable must be adjusted after completing the en- rect torque. gine cylinder head installation (refer to Group 21, (f) If not already done, clean and mark each bolt Transmissions for the proper procedures). with a dab of paint after tightening. Should you en- (21) Install the temperature sending unit and con- counter bolts which were painted in an earlier ser- nect the wire connector. vice operation, replace them. (22) Connect the fuel pipe and vacuum advance hose. (23) Connect negative cable to battery. (24) Connect the upper radiator hose and heater hose at the engine thermostat housing. (25) Fill the cooling system. Check for leaks. WARNING: USE EXTREME CAUTION WHEN THE ENGINE IS OPERATING. DO NOT STAND IN DIRECT LINE WITH THE FAN. DO NOT PUT HANDS NEAR THE PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING. Fig. 7 Engine Cylinder Head Bolt Tightening Sequence (26) Operate the engine with the radiator cap off. (6) Install the ignition coil and bracket assembly. Inspect for leaks and continue operating the engine (7) Connect the temperature sending unit wire until the engine thermostat opens. Add coolant, if re-connector. quired. (8) Install the spark plugs and tighten to 37 N⅐m(27 ft. lbs.) torque. Connect the ignition wires. VALVES AND VALVE SPRINGS (9) Install the intake and engine exhaust mani- This procedure is done with the engine cylinderfolds (refer to Group 11, Exhaust System and Intake head removed from the block.Manifold for the proper procedures). REMOVAL (10) Install the fuel lines and the vacuum advance (1) Remove the engine cylinder head from the cyl-hose. inder block. (11) If equipped, attach the power steering pump (2) Use Valve Spring Compressor Tooland bracket. MD-998772A and compress each valve spring. (12) Install the push rods, rocker arms, pivots and (3) Remove the valve locks, retainers, springs andbridges in the order they were removed. valve stem oil seals. Discard the oil seals. (13) Install the engine cylinder head cover. (4) Use an Arkansas smooth stone or a jewelers (14) Attach the air conditioner compressor mount- file to remove any burrs on the top of the valve stem,ing bracket to the engine cylinder head and block. especially around the groove for the locks.Tighten the bolts to 40 N⅐m (30 ft. lbs.) torque. (5) Remove the valves, and place them in a rack in (15) Attach the air conditioning compressor to the the same order as removed.bracket. Tighten the bolts to 27 N⅐m (20 ft. lbs.)torque. VALVE CLEANING Clean all carbon deposits from the combustionCAUTION: The serpentine drive belt must be routed chambers, valve ports, valve stems, valve stemcorrectly. Incorrect routing can cause the water guides and head.pump to turn in the opposite direction causing the Clean all grime and gasket material from the en-engine to overheat. gine cylinder head machined gasket surface.
  23. 23. ZJ 4.0L ENGINE 9 - 23INSPECTION Inspect for cracks in the combustion chambers andvalve ports. Inspect for cracks on the exhaust seat. Inspect for cracks in the gasket surface at eachcoolant passage. Inspect valves for burned, cracked or warpedheads. Inspect for scuffed or bent valve stems. Replace valves displaying any damage.VALVE REFACING (1) Use a valve refacing machine to reface the in-take and exhaust valves to the specified angle. (2) After refacing, a margin of at least 0.787 mm(0.031 inch) must remain (Fig. 8). If the margin isless than 0.787 mm (0.031 inch), the valve must be Fig. 9 Measurement of Valve Seat Runoutreplaced. When the valve stem guide clearance is excessive, the valve guide bores must be reamed oversize. Ser- vice valves with oversize stems are available in 0.076 mm (0.003 inch) and 0.381 mm (0.015 inch) incre- ments. Corresponding oversize valve stem seals are also available and must be used with valves having 0.381 mm (0.015 inch) oversize stems, 0.076mm (.003in.) oversize stems do not require oversize seals. If the valve guides are reamed oversize, the valve seats must be ground to ensure that the valve seat is concentric to the valve guide. VALVE STEM-TO-GUIDE CLEARANCE MEASUREMENT Valve stem-to-guide clearance may be measured by either of the following two methods. Fig. 8 Valve Facing MarginVALVE SEAT REFACING PREFERRED METHOD: (1) Install a pilot of the correct size in the valve (1) Remove the valve from the head.guide bore. Reface the valve seat to the specified an- (2) Clean the valve stem guide bore with solventgle with a good dressing stone. Remove only enough and a bristle brush.metal to provide a smooth finish. (3) Insert a telescoping gauge into the valve stem (2) Use tapered stones to obtain the specified seat guide bore approximately 9.525 mm (.375 inch) fromwidth when required. the valve spring side of the head (Fig. 10). (3) Control valve seat runout to a maximum of (4) Remove and measure telescoping gauge with a0.0635 mm (0.0025 in.)—(Fig. 9). micrometer.VALVE STEM OIL SEAL REPLACEMENT (5) Repeat the measurement with contacts length- Valve stem oil seals are installed on each valve wise to engine cylinder head.stem to prevent rocker arm lubricating oil from en- (6) Compare the crosswise to lengthwise measure-tering the combustion chamber through the valve ments to determine out-of-roundness. If the measure-guide bores. One seal is marked INT (intake valve) ments differ by more than 0.0635 mm (0.0025 in.),and the other is marked EXH (exhaust valve). ream the guide bore to accommodate an oversize Replace the oil seals whenever valve service is per- valve stem.formed or if the seals have deteriorated. (7) Compare the measured valve guide bore diam- eter with specifications (7.95-7.97 mm or 0.313-0.314VALVE GUIDES inch). If the measurement differs from specification The valve guides are an integral part of the engine by more than 0.076 mm (0.003 inch), ream the guidecylinder head and are not replaceable. bore to accommodate an oversize valve stem.
  24. 24. 9 - 24 4.0L ENGINE ZJ VALVE SPRING TENSION TEST Use Universal Valve Spring Tester and a torque wrench to test each valve spring for the specified ten- sion value (Fig. 12). Replace valve springs that are not within specifica- tions.Fig. 10 Measurement of Valve Guide Bore Diameter Fig. 12 Valve Spring TesterALTERNATIVE METHOD: INSTALLATION (1) Use a dial indicator to measure the lateral (1) Thoroughly clean the valve stems and the valvemovement of the valve stem (stem-to-guide clear- guide bores.ance). This must be done with the valve installed in (2) Lightly lubricate the stem.its guide and just off the valve seat (Fig. 11). (3) Install the valve in the original valve guide (2) Correct clearance is 0.025-0.0762 mm (0.001- bore.0.003 inch). If indicated movement exceeds the spec- (4) Install the replacement valve stem oil seals onification ream the valve guide to accommodate an the valve stems. If the 0.381 mm (0.015 inch) over-oversize valve stem. size valve stems are used, oversize oil seals are re- Valve seats must be ground after reaming the quired.valve guides to ensure that the valve seat is (5) Position the valve spring and retainer on theconcentric to the valve guide. engine cylinder head and compress the valve spring with Valve Spring Compressor Tool MD-998772A. (6) Install the valve locks and release the tool. (7) Tap the valve spring from side to side with a hammer to ensure that the spring is properly seated at the engine cylinder head. Also tap the top of the retainer to seat the valve locks. (8) Install the engine cylinder head. VALVE TIMING Disconnect the spark plug wires and remove the spark plugs. Remove the engine cylinder head cover. Remove the capscrews, bridge and pivot assembly, and rocker arms from above the No.1 cylinder. Alternately loosen each capscrew, one turn at aFig. 11 Measurement of Lateral Movement of Valve time, to avoid damaging the bridge. Stem Rotate the crankshaft until the No.6 piston is at top dead center (TDC) on the compression stroke. Rotate the crankshaft counterclockwise (viewed from the front of the engine) 90°.

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