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I've heard people say if you don't know when the belt was last changed sometimes you can look at the belt and tell what condition it is in and whether it should be able to last longer. However I've also been told that you cannot know whether it's in good condition because the belt can be worn or damaged internally and this wont be visible outwardly so it can still snap. Which is true?

James Wilson
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  • Just change it - the cost of the new belt plus labor is much less than the cost of damage... and both can be true... – Solar Mike Jan 03 '19 at 07:22

4 Answers4

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Once a belt has been on for a short period you can't really tell its age, as the ID and manufacturer lettering is wearing away as soon as the belt is in operation.

If you don't know or have no history on a cambelts replacement date, it's best to change it. As you just can't tell what condition structurally they are in.

Orb
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While some forms of extreme wear can be visible in the form of cracking the majority can't be seen while the belt is in situ and if the wear gets to the point where it is visible it's way, say overdue. If there's any doubt as to whether it was last changed at the appropriate interval then just get it changed ASAP.

While usually not a cheap service to have done the cost of a failure dwarfs it.

motosubatsu
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The belt itself may not be the life limiting feature anyway.

I once had a car where the manufacturers reduced the recommended timing belt change interval, because some "clever" engineer had decided to use plastic pulleys for tensioning, and they started to crack before the belt reached the end of its life.

Of course they didn't change the pulleys to something more durable to fix the problem - they just made the customers pay for more frequent servicing!

alephzero
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It is possible to visually see damage to the timing belt that would indicate it is liable to fail soon and ought to be replaced ahead of the recommended schedule. This type of damage would include cuts to the belt, wear so that the "teeth" can be seen through the back-side of the belt as it crosses the pulleys, fraying at the edges of the belt or cracking of the rubber.

If you observe any of these signs on a timing belt, order a replacement and fit it immediately. Do not wait until the vehicle reaches it's suggested interval for replacement. If you do not know how far into the current interval the vehicle is, assuming it's mileage and age exceeds the first replacement interval; replace it.

It is not an acceptable assumption that if the belt "looks okay" that it can be left. In summary, replace a visually damaged belt, replace a belt when it hits it's service interval and replace a belt that is of an unknown vintage or mileage.

Steve Matthews
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