service repair manual

1. Original InstructionsCopyright DOOSAN 2015
Serial Number 1001 and Up
Shop Manual
DX235NLC-5 Excavator
950106-01115E
January 2015
DOOSAN and the DOOSAN logo are registered
trademarks of DOOSAN Corporation in the United
States and various other countries around the
world.

2. Table of Contents
Page I
1Table of Contents
1 Safety 1 Track Excavator Maintenance Safety
2 Specifications 1 Specifications
3 General Maintenance 1 General Maintenance Instructions
2 Standard Torques
4 Engine 1 Engine
5 Upper Structure 1 Cabin
2 Counterweight
3 Hydraulic Oil Tank
4 Fuel Tank
5 Main Pump
6 Drive Coupling (Main Pump)
7 Main Control Valve
8 Swing Device
9 Joystick Valve (Work Lever)
10 Travel Control Valve (with Damper)
11 Solenoid Valve
12 EPPR Valve (One or Two-way)
13 Accumulator
14 Gear Pump (Rotating)
15 One Spool Valve (Rotating)

3. Table of Contents
Page II
6 Lower Structure and Chassis 1 Swing Bearing
2 Center Joint
3 Travel Device
4 Track Assembly
7 Front 1 Boom and Arm
2 Bucket
3 Cylinders
8 Hydraulic System 1 Hydraulic System
2 Hydraulic System Testing and Adjustment
3 Hydraulic System Troubleshooting
9 Electrical System 1 Electrical System
10 Options 1 One Way
2 Two-way
3 Rotating
4 Quick Coupler
5 Two Pump
11 Schematic 1 Hydraulic Schematic/Electrical Schematic

4. Track Excavator Maintenance Safety
1-1-1
DX235NLC-5
Track Excavator
Maintenance
Safety
Edition 1

5. Track Excavator Maintenance Safety
1-1-5
DX235NLC-5
SAFETY INSTRUCTIONS
SAFETY MESSAGES
Replace with Safety Messages Section on pages III and IV in
the Doosan Operation & Maintenance Manual.
WARNING
AVOID DEATH OR SERIOUS INJURY
Instructions are necessary before operating or servicing
machine. Read and understand the Operation &
Maintenance Manual and signs (decals) on machine. Follow
warnings and instructions in the manuals when making
repairs, adjustments or servicing. Check for correct
function after adjustments repairs or service. Untrained
operators and failure to follow instructions can cause death
or serious injury.

6. DX235NLC-5Track Excavator Maintenance Safety
1-1-6
GENERAL
Safe Operation is Operator's
Responsibility
Only trained and authorized personnel should operate and
maintain the machine.
Follow all safety rules, regulations and instructions when
operating or performing maintenance on machine.
• Do not operate machine if you are under the influence of
drugs or alcohol. An operator who is taking prescription
drugs must get medical advice to determine if he or she
can safely operate a machine.
• When working with other personnel on a work site, be sure
that all personnel know nature of work and understand all
hand signals that are to be used.
• Be sure that all guards and shields are installed in their
proper location. Have guards and shields repaired or
replaced immediately if damaged.
• Be sure that you understand the use and maintenance of
all safety features such as safety lever and seat belt. Use
them properly.
• Never remove, modify or disable any safety features.
Always keep them in good operating condition.
• Always check for and know the location of underground
and overhead utility lines before excavating.
• Failure to use and maintain safety features according to
instructions in this manual, Safety Manual and Shop
Manual can result in death or serious injury.
Know Your Machine
Know how to operate your machine. Know the purpose of all
controls, gauges, signals, indicators and monitor displays. Know
the rated load capacity, speed range, braking and steering
characteristics, turning radius and operating clearances. Keep in
mind that rain, snow, ice, loose gravel, soft ground, slopes etc.,
can change operating capabilities of your machine.

7. Track Excavator Maintenance Safety
1-1-7
DX235NLC-5
Proper Work Tools and Attachments
Only use work tools and attachments that are recommended by
DOOSAN for use on DOOSAN machines. When installing and
using optional attachments, read instruction manual for
attachment, and general information related to attachments in this
manual. Because DOOSAN cannot anticipate, identify or test all
attachments that owners may want to install on their machines,
contact DOOSAN for written authorization and approval of
attachments, and their compatibility with optional kits.
Attachments and attachment control systems that are
compatible with the machine are required for safe and reliable
machine operation. Do not exceed maximum operating weight
(machine weight plus attachment) that is listed on ROPS
certification plate.
Make sure that all guards and shields are in place on machine
and on work tool. Depending on type or combination of work
equipment, there is a potential that work equipment could
interfere with the cabin or other parts of machine. Before using
unfamiliar work equipment, check if there is any potential of
interference, and operate with caution.
While you are performing any maintenance, testing, or
adjustments to attachments, stay clear of the following areas:
cutting edges, pinch points, and crushing surfaces.
Never use attachment as a work platform or manlift.
Contact your DOOSAN distributor about auxiliary hydraulic kits
for attachments installation. If you are in doubt about
compatibility of a particular attachment with a machine, consult
your DOOSAN distributor.
Pressurized Fluids
Pressurized air or fluids can cause debris and/or fluids to be
blown out. This could result in death or serious injury.
Immediately after operations are stopped, coolant, engine oil,
and hydraulic oil are at their highest temperatures and the
radiator and hydraulic tank are still under pressure. Always wait
for temperature to cool down. Follow specified procedures when
attempting to remove caps, drain oil or coolant, or replacing
filters. Always wait for temperature to cool down, and follow
specified procedures when performing these operations. Failure
to do so can result in death or serious injury.
When pressurized air and/or pressurized water is used for
cleaning, wear protective clothing, protective shoes, and eye
protection. Eye protection includes goggles or a protective face
shield.
Pressure can be trapped in a hydraulic system and must be
relieved before maintenance is started.
Releasing trapped pressure can cause sudden machine
movement or attachment movement. Use caution if you
disconnect hydraulic lines or fittings.
FG018457
Figure 1

8. DX235NLC-5Track Excavator Maintenance Safety
1-1-8
High-pressure oil that is released can cause a hose to whip or oil
to spray. Fluid penetration can result in death or serious injury. If
fluid enters skin or eyes, get immediate medical attention from a
physician familiar with this injury.
Obey all local laws and regulations for disposal of liquids.
To prevent hot coolant from spraying out, stop engine and wait
for coolant to cool. Using gloves, slowly loosen cap to relieve
pressure.
Flying or Falling Objects
On work sites where there is a potential hazard that flying or
falling objects can hit operator's cabin, select and use a guard to
match operating conditions for additional operator protection.
Working in mines, tunnels, deep pits, and loose or wet surfaces,
could produce hazard of falling rocks or flying objects. Additional
protection for operator's cabin could be required such as an
Operator Protection Guard (OPG) or window guards. Contact
your DOOSAN distributor for information on available protective
guards.
To prevent personnel from being struck by flying objects, keep
personnel out of work area.
HAOA110L
Figure 2
HAOA100L
Figure 3

9. DX235NLC-5Engine
4-1-1
Engine
Edition 1

10. Engine
4-1-5
DX235NLC-5
SAFETY INSTRUCTIONS
WARNING
AVOID DEATH OR SERIOUS INJURY
Instructions are necessary before operating or servicing
machine. Read and understand the Operation &
Maintenance Manual and signs (decals) on machine. Follow
warnings and instructions in the manuals when making
repairs, adjustments or servicing. Check for correct
function after adjustments repairs or service. Untrained
operators and failure to follow instructions can cause death
or serious injury.

11. DX235NLC-5Engine
4-1-6
OVERVIEW
FRONT
EX1403491
Figure 1

12. Engine
4-1-7
DX235NLC-5
GENERAL INFORMATION
General Description
This manual provides the most efficient methods for engine
maintenance as well as quick, efficient methods to determine
the cause of engine faults to ensure that any actions taken by
professionally certified maintenance technicians are done in the
most efficient and efficient way possible. If maintenance is
performed by unskilled technicians, or maintenance without the
specified tools and facilities, serious bodily injury or critical faults
in engine performance may occur. Regular inspection and
maintenance are required to maintain long-term optimal engine
conditions and best performance. In the event that a part must
be replaced, only genuine parts as defined by the parts the list
(Parts Book) should be used. Doosan shall not be held liable for
any critical damage or faults which may be caused by the use of
unauthorized or remanufactured parts. The maintenance
methods stated in this Operation and Maintenance Manual are
the most efficient and safest work procedures. Some work
procedures require special tools.
For questions about genuine parts and special tools, please
contact us.
This manual includes 'Danger', 'Warning', and 'Caution' in order
to reduce possible injuries and engine faults which may occur
while performing maintenance. If workers do not follow the
instructions, critical faults in engine performance and operation
or serious bodily injury may occurred. 'Danger', 'Warning', and
'Caution' instructions must be followed. However, we inform you
that it is not possible to describe all possible and unexpected
dangers which may arise while performing engine maintenance.
Cautions for Starting the Engine
1. Before starting the engine, please read this manual
carefully and fully understand 'Danger', 'Warning', and
'Caution'. If you cannot fully understand it or have any
question, please contact us.
2. For safety reasons, attach "Warning" signs around engines
in operation to keep people other than workers from
accessing the engines. Let engine operators know that
they are responsible for the safety of the engine room.
3. Only authorized people may start and operate engines.
Unauthorized people should not be allowed to handle
engines.
4. Do not access running or rotating parts while the engine is
in operation.
5. Be careful not to touch or contact the engine during
operation since it becomes hot during operation.
6. Exhaust gas is poisonous. Fully ventilate before starting
engine. If the space is airtight, ensure that it is well ventilated.

13. DX235NLC-5Engine
4-1-8
Cautions for Inspection and Repair
1. Inspection and repair of engine should be performed only
when the engine is stopped. Otherwise, burns or safety
accidents may occur, so do not perform inspection or
repair while the engine is running.
2. If it is absolutely necessary to perform inspection or repair
on the operating engine, do not get close to the rotating
parts.
3. Use an engine oil drain container that is large enough to
prevent the overflow of engine oil while draining engine oil.
4. Open the engine coolant cap after fully cooling the engine
to exchange or replenish coolant.
5. Fuel is highly flammable. Smoking or use of fire around an
engine may cause fire.
DANGER
AVOID DEATH
When accessories such as necklaces, rings, watches,
or gloves become stuck in rotating parts while the
engine is running, serious bodily injury may occur.
WARNING
AVOID DEATH OR SERIOUS INJURY
Do not exchange or disassemble a pipe or horse (from
the engine fuel circuit, engine oil circuit, coolant
circuit, or compressed air circuit) while the engine is
running. The leaked liquid may cause bodily injuries.
WARNING
AVOID DEATH OR SERIOUS INJURY
If the coolant cap is opened while the engine is still hot,
hot water will spurt out and may cause burns. Open the
engine coolant cap after fully cooling the engine.
WARNING
AVOID DEATH OR SERIOUS INJURY
Only refuel when the engine is stopped.

14. Engine
4-1-9
DX235NLC-5
6. Mark and separately manage the containers for storing
coolant from beverage containers for avoiding confusion.
See a doctor immediately in case of drinking coolant.
7. Follow the instructions provided by the battery
manufacturer when checking or handling batteries.
8. Only certified professional technicians should repair and
maintain engines.
9. Only appropriate tools should be used. If the jaws of a
wrench are worn out, the wrench might slip during use,
causing safety accidents.
10. Do not allow other persons to stay or pass under an engine
when lifting the engine with a crane. Before lifting the
engine, ensure that there is no one around the engine and
reserve enough safety space.
11. Before inspecting or replacing the electrical apparatus,
disconnect the battery ground wire first. Connect the
battery ground wire after completing all required work for
checking or replacing the electrical apparatus in order to
prevent a short circuit.
12. Before performing electric welding works, turn off engine,
block the power supply to the engine, and remove the wire
harness connector connected to the engine control unit
(ECU).
13. Do not give any electric or mechanical shocks or perform
welding works on the electrical apparatus or the ECU.
General Repair
1. Wait until the engine is properly cooled down before starting
work, since you may get burned by the heated engine.
Before performing fuel line work, check the common rail
pressure and engine temperature by using the failure
diagnosis device.
2. Disconnect the battery ground wire from to prevent
damage of wires and sensors caused by a short circuit.
3. Engine oil and coolant may damage paint and should be
stored in a separate container and marked for safe
management.
4. Store the disassembled parts in a specified space to avoid
damage or pollution.
WARNING
AVOID DEATH OR SERIOUS INJURY
Battery fluid is corrosive and dangerous because of its
explosiveness and toxicity. Therefore, it should only
be handled by a skilled technician who specializes in
battery fluid.

15. DX235NLC-5Engine
4-1-28
ENGINE DISASSEMBLY
Engine Disassembly
Disassemble the engine according to the following procedure:
1. Drain coolant.
A. Check that the engine and radiator is sufficiently
cooled down.
B. Place a container in front of the coolant drain plug.
C. Remove the radiator cap.
D. Open the drain valve on the bottom of the radiator to
drain coolant.
E. Remove the coolant drain plugs from the cylinder
block and oil cooler.
F. Drain coolant into the prepared container.
G. After draining coolant, install the drain plug.
CAUTION
AVOID INJURY
• Prepare the necessary tools and genuine parts before
engine disassembly.
• Prepare a shelf to keep removed parts.
• Keep the working area well lighted and clean.
• Keep your hands clean at all times during service.
• Keep parts removed from the engine in the removal
order.
• Make sure that removed parts are not mixed and do
not touch each other.
EX1404285Figure 10
EX1404306
Figure 11
DANGER
AVOID DEATH
• Never open the radiator cap while the engine is hot.
If opening the radiator cap while the engine is still
hot, hot coolant may spurt, resulting in a severe
burn. Open the radiator cap after confirming that
the engine is sufficiently cooled down.
• Put a label on the coolant container not to get
mixed with other containers. If you swallow coolant,
seek professional medical help immediately.

16. Engine
4-1-29
DX235NLC-5
2. Separate the dipstick.
A. Pull out the dipstick.
3. Drain engine oil.
A. Place a container under the engine to collect drained
engine oil.
B. Remove the drain plug from the oil pan and drain
engine oil into the prepared container.
C. Remove the oil filler cap.
D. Remove the engine oil filter.
E. After draining engine oil, install the engine oil filter
and drain plug.
WARNING
AVOID DEATH OR SERIOUS INJURY
Used coolant should be discarded according to the
local regulations. Never discard used engine oil to the
ground, ditch, sewer, river, sea, etc. Such action can
pollute the environment. Discarding used engine oil
improperly can result in punishment due to violation of
the corresponding regulation.
CAUTION
AVOID INJURY
When changing coolant, make sure that it is not left on
any belt or electric part.
Drain Valve EX1403623
Figure 12
WARNING
AVOID DEATH OR SERIOUS INJURY
Used oil should be discarded according to the local
regulations. Never discard used engine oil to the
ground, ditch, sewer, river, sea, etc. Such action can
pollute the environment. Discarding used engine oil
improperly can result in punishment due to violation of
the corresponding regulation.

17. DX235NLC-5Engine
4-1-30
4. Remove the intercooler.
A. Remove all the hoses and air pipes from the
intercooler.
B. Unscrew the intercooler mounting bolts to remove the
intercooler.
5. Remove the cooling fan.
A. Remove the fan guide and bracket.
B. Unscrew the flange mounting bolt to remove the
flange and cooling fan.
6. Remove the belt.
A. Unscrew the tension adjusting bolts and mounting
bolts of the A/C compressor, air compressor and
alternator.
B. Remove the belt.
7. Remove the engine from the machine.
8. Disconnect the cables and harnesses of the engine from
each sensor.
9. Remove the alternator and A/C compressor.
A. Unscrew the mounting bolt to remove the alternator.
B. Unscrew the idle puller mounting bolt to remove the
A/C compressor.
Hot Air by
Turbo Charger
Compressor
Air Flow by
Cooling Fan
Cooled Air to
Intake Stake
EX1404312
Figure 13
EX1403625
Electronic
Clutch
Cooling Fan
Figure 14
EX1403626
Figure 15
Aircon Compressor
Alternator
EX1403627
Figure 16

18. Engine
4-1-31
DX235NLC-5
10. Remove the breather.
A. Unscrew the mounting clamp screw to disconnect the
rubber hose.
B. Remove the breather valve assembly.
11. Disconnect the air pipe and remove the air heater.
A. Unscrew the mounting bolt to disconnect the air pipe
and remove the air heater.
12. Remove the fuel filter.
A. Unscrew the hollow screw from the fuel filter and
disconnect the fuel hose.
B. Unscrew the fuel filter mounting bolt to remove the
fuel filter.
13. Disconnect the intake stake.
A. Unscrew the mounting bolt to disconnect the air
hose.
EX1403628
Figure 17
EX1403629
Figure 18
CAUTION
AVOID INJURY
Never let foreign materials enter the turbocharger.
EX1403630
Figure 19
EX1403631
Figure 20

19. DX235NLC-5Engine
4-1-32
14. Separate the intake manifold.
A. Unscrew the intake manifold mounting bolts to
remove the intake manifold from the cylinder block.
B. Remove the gasket and clean the gasket mounting
surface thoroughly with a scraper.
15. Remove the common rail and high-pressure pipe.
A. Disconnect the high-pressure pipe between the fuel
high-pressure connector and common rail.
B. Unscrew the common rail mounting bolts to remove
the common rail.
16. Remove the fuel high-pressure pump.
A. Unscrew the fuel high-pressure pump mounting bolts
to remove the fuel high-pressure pump.
EX1403632
Figure 21
EX1403633
Figure 22
CAUTION
AVOID INJURY
• Seal the common rail thoroughly after removing it
to prevent foreign materials from entering it.
• Once the fuel high-pressure pipe is
disconnected, it cannot be reused.
EX1403634
Figure 23

20. Engine
4-1-33
DX235NLC-5
17. Remove the EGR valve.
A. Unscrew the EGR valve mounting bolts to remove
the EGR valve and exhaust manifold.
B. Unscrew the mounting bolts to remove the exhaust
pipe from the EGR cooler.
C. Disconnect the coolant pipe from the EGR valve.
18. Remove the EGR cooler.
A. Unscrew the EGR cooler and bracket connecting bolt
to separate the EGR cooler.
B. Disconnect the pipe and hose from the EGR cooler.
19. Remove dosing module.
Unscrew the mounting bolt of the dosing module to remove
it from the UREA tank.
EX1403635
Figure 24
CAUTION
AVOID INJURY
Seal the EGR valve and exhaust pipe thoroughly after
removing them to prevent foreign materials from
entering them.
EX1403636
Figure 25
EX1403637
Figure 26
CAUTION
AVOID INJURY
Seal the EGR cooler thoroughly after removing it to
prevent foreign materials from entering it.
EX1404191
Figure 27

21. DX235NLC-5Engine
4-1-34
20. Remove the turbocharger.
A. Disconnect the intake stake from the turbocharger.
B. Disconnect the coolant hose from the turbocharger.
C. Disconnect the oil feed pipe and oil drain pipe
between the cylinder block and turbocharger.
D. Unscrew the turbocharger mounting bolts to separate
the turbocharger from the exhaust manifold.
21. Remove the exhaust manifold.
A. Unscrew the exhaust manifold mounting bolts to
remove the exhaust manifold.
22. Disconnect the coolant pipe and thermostat.
A. Unscrew the coolant pipe mounting bolt to disconnect
the coolant pipe from the thermostat housing.
B. Remove the coolant thermostat and O-ring.
C. Clean the gasket mounting surface of the coolant
pipe with a scraper thoroughly.
EX1404192
Figure 28
EX1403642
Figure 29
CAUTION
AVOID INJURY
Do not reuse the removed gasket.
EX1403643
Figure 30
CAUTION
AVOID INJURY
Make sure that the gasket residual does not enter the
coolant passage.

22. Engine
4-1-35
DX235NLC-5
23. Remove the coolant pump.
A. Unscrew the bracket mounting bolts for the coolant
pump and oil cooler.
B. Unscrew the bolt (1 ea) for the oil cooler.
C. Unscrew the coolant pump mounting bolts to remove
the coolant pump.
D. Remove the O-ring for the coolant pump.
24. Remove the start motor.
A. Unscrew the start motor mounting nut and remove
the start motor with care. Be careful not to damage its
gear.
25. Remove the oil filter.
A. Remove the oil filter cartridge using a special service
tool.
EX1403644
Figure 31CAUTION
AVOID INJURY
Do not reuse the O-ring.
EX1403645
Figure 32
EX1403646
Figure 33
Oil Cooler
Oil Filter
EX1403647
Figure 34

23. DX235NLC-5Engine
4-1-36
26. Remove the vibration damper.
A. Unscrew the mounting bolts of the vibration damper
and crank pulley in the reverse order to remove the
vibration damper assembly.
27. Remove the cylinder head cover.
A. Unscrew the cylinder head cover mounting bolts to
remove the cylinder head cover.
B. Unscrew the intermediate cover mounting bolts to
remove the intermediate cover.
28. Remove the rocker arm.
A. Unscrew the rocker arm bracket mounting bolts in the
reverse order to remove the rocker arm assembly.
29. Remove the push rod.
A. Remove the push rod.
EX1403648
Figure 35
EX1403649
Figure 36
EX1403650
Figure 37
EX1403651
Figure 38

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25. Engine
4-1-37
DX235NLC-5
30. Remove the fuel injector.
A. Unscrew the fuel high-pressure connector mounting
bolts to disconnect the fuel high-pressure connector.
B. Remove the harness from the injector.
C. Unscrew the injector mounting bracket bolts to
remove the injector.
D. Remove the seal ring from the nozzle hole from the
cylinder head.
31. Remove the cylinder head.
A. Unscrew the cylinder head bolts in the reverse order
of tightening to remove the cylinder head.
– Step 1: Unscrew the bolt for 1 to 2 threads.
– Step 2: Unscrew the bolt completely to remove it.
B. Remove the cylinder head bolts in these two steps.
C. Keep the removed bolts in order with care, being
careful not to damage their threads.
D. Remove the cylinder head gasket.
E. Remove foreign materials from the surface of the
cylinder head and block.
Fixing Bracket
BoltsInjector Type
O-ring
Seal Ring
EX1403652
Figure 39
CAUTION
AVOID INJURY
Be careful not to damage the nozzle during removing
the injector.
CAUTION
AVOID INJURY
To remove the injector, unscrew the fuel high-pressure
connector mounting nut to disconnect the fuel high-
pressure connector completely. Then, unscrew the
caliper mounting bolt to remove the injector.
Head Bolt
Lifting Hook
EX1403741
Figure 40
CAUTION
AVOID INJURY
Make sure that the bolts are not hit by each other.

26. DX235NLC-5Engine
4-1-38
F. Unscrew the mounting bolt of the lifting hook from the
cylinder head to remove the lifting hook.
32. Remove the valve and valve stem seal.
A. Press the valve spring and retainer with the valve
spring compressor to remove the valve cotter.
B. Remove the valve spring and retainer.
C. Remove the calipers.
D. Use a general service tool to remove the valve stem
seal.
E. Remove valve.
F. Unscrew the mounting bolt of the lifting hook from the
cylinder block to remove the lifting hook.
33. Remove the oil cooler.
A. Unscrew the oil cooler mounting bolts to remove the
oil cooler.
CAUTION
AVOID INJURY
Be careful not to damage the mating surface.
Valve Spring
Copression Jig
EX1403742
Figure 41
CAUTION
AVOID INJURY
Do not reuse the valve stem seal.
EX1403743
Figure 42
EX1403653
Figure 43

27. Engine
4-1-39
DX235NLC-5
34. Remove the oil pan.
A. Unscrew the oil pan mounting bolts to remove the oil
pan.
B. Remove the oil pan gasket.
35. Remove the front oil seal and cover.
A. Remove the oil seal using a oil seal removing tool.
B. Unscrew the gear case cover mounting bolt to
remove the oil seal cover.
36. Remove the oil pump and disconnect the pipe.
A. Unscrew the oil suction pipe mounting bolt to remove
the bracket.
B. Unscrew the oil pump pipe mounting bolts to
disconnect the suction pipe and feed pipe.
C. Unscrew the oil pump mounting bolts to remove the
oil pump.
37. Remove the flywheel.
A. Unscrew the flywheel mounting bolts and install the
guide bolt to remove the flywheel.
B. Unscrew the bolts in the reverse order of their
tightening to remove the flywheel.
Oil Pan Fixing Bolt
EX1403654
Figure 44
EX1403655
Figure 45
EX1403656
Figure 46
EX1403657
Figure 47