Timing Belt: Testing and Inspection

Inspection
1. Inspect the belt closely. If the following problems are evident, replace the belt with a new one.






1) Hardened back surface of rubber Back surface is glossy, non-elastic and so hard that when the nail of your finger is pressed into it, no mark is produced.






2) Cracked back surface of rubber.






3) Side of belt is badly worn.

Note: A belt in good condition should have clear-cut sides as if it were cut with a sharp knife.

4) Teeth are badly worn out.
Initial stage: Canvas on load side of the tooth flank worn (fluffy canvas fibers, rubber gone, color changed to white, and unclear canvas texture)
Last stage: Canvas on the load side of the tooth flank worn down and rubber exposed (tooth width reduced).






5) Missing tooth






2. If backlash or an irregular noise is observed when rotating the pulley, replace the timing belt tensioner and idler pulley.