© 2012 Delmar, Cengage Learning

Automotive Hoses

Chapter 23

© 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

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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

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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

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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

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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

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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

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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

© 2012 Delmar, Cengage Learning

© 2012 Delmar, Cengage Learning

© 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

© 2012 Delmar, Cengage Learning

© 2012 Delmar, Cengage Learning

© 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

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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

© 2012 Delmar, Cengage Learning

© 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

© 2012 Delmar, Cengage Learning

© 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