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Automotive Belts

Chapter 22

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Objectives• Explain the differences between V-belts, V-

ribbed belts, and timing belts• Inspect and evaluate the condition of all types of

belts• Correctly remove and replace all types of belts

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Introduction• Accessories are usually driven with a belt from

the crankshaft– Pumps and air-conditioning compressors driven

by V-belt or V-ribbed serpentine belt– On some engines, the camshaft is also driven by

a timing belt

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Belt Material• Belts are strong and flexible with tensile cords

– Overcord material on top of belt– Undercord supports the cord and transfers load

to pulleys– Tensile cords prevent the belt from sagging in

the middle– Some belts are made of neoprene or chloropene

• Oil-resistant, artificial rubber

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V-Belt• More surface area contact than the same width

flat belt– Must be the correct size

• V-belt cords– Strength: determined by tensile cord placement– High cordline belts are stronger

• Require more material to manufacture– Center cord belts are cheaper

• Do not last as long– Some use dual belts to drive accessories

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V-Ribbed Belts• Ribbed on one side

– Thinness of the belt makes it more flexible– Usually the ribbed side matches the pulley

grooves of accessories– Flat side goes against a spring-loaded tensioning

roller

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Serpentine Belt Drive• Serpentine belt drive systems

– Belt follows a snake-like path– One belt operates all accessories– Easier to install than V-belts– Take up less space – Transmit power more efficiently – Last longer

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Stretch Belts• Do not require a belt

tensioner– Used to drive the air-

conditioning compressor from the crankshaft pulley

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Timing Belts• On some overhead cam engines, a timing belt

drives the camshaft– Quieter than a timing chain– Do not require lubrication– More efficient– Resist stretching

• Timing belts – Have very strong fiberglass cordline and rubber-

impregnated molded teeth

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Drive Belt Service• Considerations

– Replace at reasonable intervals• Keep them strong and dependable

– Change them before they fail• Failed water pump drive belt can cause engine

failure– Failures rise significantly after four years of use

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Belt Inspection and Adjustment• Serpentine belt fails

– Cooling system, electrical systems, and power steering cease

• Inspecting belts– Cracking– Pulley grooves for oil, rust, or wear

• Belt alignment – Misalignment: parallel and angular

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Replacing Belts• Considerations

– Disconnect the battery– Be sure the new belt is the right size

• Use string in the pulley groove to estimate the size• Belt sizes change in ½ inch increments

• V-ribbed pulley grooves– Count the number of grooves on a pulley being

replaced

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Belt Tension• Important for long belt life

– Belts stretch slightly in the first few minutes of operation

• If overtightened, parts can be overloaded– Slipping belt can result in

several problems

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Belt Tension (cont'd.)• Spring-loaded tensioner inspection

– Inspect turning for resistance– Check tensioner arm for looseness

• Spring-loaded tensioner internal damper– Acts like a brake on the tensioner arm– Minimizes pulsations on the belt drive system

• V-ribbed belt replacement– Make a sketch before removal

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Belt Tension (cont'd.)• V-belt tension

– Set new V-belt tension to 15 pounds higher than recommended

– Recheck and adjust• V-ribbed belt tension

– Use a click-type tension gauge

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© 2012 Delmar, Cengage Learning© 2012 Delmar, Cengage Learning