© 2012 Delmar, Cengage Learning Automotive Belts Chapter 22

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

Automotive Belts

Chapter 22


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


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


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


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


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


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



Stretch Belts• Do not require a belt

tensioner– Used to drive the air-

conditioning compressor from the crankshaft pulley


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


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


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


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


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


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



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 Automotive Belts Chapter 22