1. © 2012 Delmar, Cengage Learning Automotive Belts Chapter 22

2. © 2012 Delmar, Cengage Learning 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

3. © 2012 Delmar, Cengage Learning 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

4. © 2012 Delmar, Cengage Learning 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

5. © 2012 Delmar, Cengage Learning 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

6. © 2012 Delmar, Cengage Learning 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

7. © 2012 Delmar, Cengage Learning 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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9. Stretch Belts Do not require a belt tensioner –Used to drive the air-conditioning compressor from the crankshaft pulley

10. © 2012 Delmar, Cengage Learning 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

11. © 2012 Delmar, Cengage Learning 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

12. © 2012 Delmar, Cengage Learning 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

13. © 2012 Delmar, Cengage Learning 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

14. © 2012 Delmar, Cengage Learning 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

15. © 2012 Delmar, Cengage Learning 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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17. 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

18. © 2012 Delmar, Cengage Learning