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1. © 2012 Delmar, Cengage Learning
Automotive Hoses
Chapter 23

2. © 2012 Delmar, Cengage Learning
Objectives
• Correctly identify automotive hose sizes
• Explain the different types of hose materials,
clamps, and their applications
• Inspect all types of hoses for damage
• Correctly remove and replace all types of hoses

3. © 2012 Delmar, Cengage Learning
Introduction
• More than ten different types of hoses
– Hoses are found on the:
• Radiator
• Heater
• Automatic transmission
• Fuel and emission systems
• Brake system
• Lubrication system
• Air-conditioning system

4. © 2012 Delmar, Cengage Learning
Hose Construction
• Hoses consist of an inner rubber tube,
reinforcement, and outer rubber cover
– Bonded with adhesives
• Different tubes and covers
– Different reinforcement
• Withstand different amounts of pressure
• Incorrect hose can result in a fire or damage
– Use caution around refrigerant lines

5. © 2012 Delmar, Cengage Learning
Hose Size
• Hoses are sized according to inside diameter
– Common heater hose sizes
• 5/8 and 3/4 inch
– Common fuel hose and line sizes
• 5/16 and 3/8 inch for pressure hoses
• 1/4 inch for return lines

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Unreinforced Hose
• Unreinforced rubber
– Used for vacuum hose, windshield washer hose,
and drain hose
• These hoses are under little strain
• Can still present safety problems if they fail
• Harden with age and are routinely replaced

7. © 2012 Delmar, Cengage Learning
Radiator Hose
• Radiator hoses designed to have a burst
strength
– Five to six times working pressure of the cooling
system

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Hose Types
• Straight: used for fuel hose, vacuum hose, or
heater hose
– Kinks when bent too much
• Curved: preformed with required bends
– Vulcanizing cures rubber and sets it in a given
shape
• Universal: clamped on one end and bent until it
assumes the desired shape
– Reinforced with wire

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Hose Types (cont'd.)
• Formable: has metal wires inside
– Allow it to be bent without kinking
• By-pass: molded to the correct curves
– Must be cut to length, depending on the
application
• Fuel hose: fuel delivery systems use metal
tubing
– Connected to tank and engine by rubber hoses
• Must resist abrasion, oil, temperature

10. © 2012 Delmar, Cengage Learning
Hose Types (cont'd.)
• Carburetor fuel hose: braided reinforcement
with synthetic rubber cover and inner tube
– Does not react to gasoline or alcohols
• Fuel injection hose: designed for higher
pressure
– Burst strength more than 900 psi
• Transmission oil cooler hose: withstand
constant temperature of 300°F and 450 psi
• Power steering hose: pressure and return line

11. © 2012 Delmar, Cengage Learning
Hose Types (cont'd.)
• Power brake booster hose: must be reinforced
and fuel-resistant
• Brake hose: must be flexible and able to
withstand high pressure
– Burst strength of 5,000 psi
– Rubber reinforced
– Brake tubing has male fittings on both ends
• Air-conditioning hose: reinforced and have
crimped connectors
– Must withstand high pressures

12. © 2012 Delmar, Cengage Learning

13. © 2012 Delmar, Cengage Learning

14. © 2012 Delmar, Cengage Learning
Hose Clamps
• Tighten hoses to their connections
– Worm gear clamps: reusable and easy to install
– Twin wire clamps: strong but may cut into the
hose if over-tightened
– Rolled edge clamps: designed not to cut into the
hose
– Screw tower clamps: strong but difficult to
remove
– Spring clamps: can cut into a hose and do not
provide a strong enough clamping force

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16. © 2012 Delmar, Cengage Learning

17. © 2012 Delmar, Cengage Learning
Hose Inspection
• Considerations
– Check hoses for hardness by bending them
– Oil causes hoses to swell and deteriorate
• Check rubber on the inside for deterioration
– Electrochemical degradation (ECD) occurs when
the hose and fittings form a galvanic cell
• Causes small cracks inside hose
• To check for ECD squeeze the hose in several
places to see if rubber feels consistent
– Any questionable hose should be replaced

18. © 2012 Delmar, Cengage Learning
Replacing Hoses
• Considerations
– Drain off coolant to replace a coolant hose
– Do not force hose if it does not come loose from
its fitting
– Ensure clamps are in good condition and tight
– Heater hoses on a car may be two diameters
• Hose should not interfere with manifolds, belts,
spark plug cables
• Hose should not be damaged by engine or
accessories
– Compare new power steering hose to old one

19. © 2012 Delmar, Cengage Learning

20. © 2012 Delmar, Cengage Learning
Replacing Hoses (cont'd.)
– Use the correct fluid when refilling the power
steering system
– Bleed air from power steering by turning the
steering wheel back and forth
– Replace fuel injector hoses before failure
• Use hoses with crimped ends
– Special hose is required for the in-tank fuel pump
– Fuel injection lines maintain pressure even when
the engine is off
– Factory-installed air-conditioning systems come
with a very wide variety of styles

21. © 2012 Delmar, Cengage Learning

22. © 2012 Delmar, Cengage Learning
Replacing Hoses (cont'd.)
• Worm gear hose clamps with 3-barb fitting is not
recommended
– Avoided with R-134A beadlock fittings