Ok, so we know that the belt/tensioner life is 40,000 miles or 4 years - whichever comes first.

I can understand why the mileage limit as that roughly equates to an amount of wear.

So, why is there a time limit as well? What is there in the belt/tensioners that is time critical and could decay to the point of causing a major failure? The 2 cambelts that I changed seemed to be in perfect condition and the tensioners/rollers felt as good as the brand new ones.

I'm thinking about cars that do low miles, why a 4 year limit and not 5 or 6?

I'm not condoning pushing ones luck - just curious as to what actually fails and why.

Thanks - Rob

From a manufacturer's point of view, a time limit has to be on the warranty anyway. Thats why everything has a time limit, as well as mileage.

In case of this, does the belt age? Grease in the bearings? Tensioner ages?

Vauxhall are just covering their backsides. It used to be 8 yrs/80 000 miles but had some tensioner failures so bottled it & halved the time/distance they should be changed.

Andy B wrote on 08. May 2011 at 22:35:


Or realised that the revised interval was too long because of failures

You fancy trying your luck going 8 yrs/80k?

IIRC Vauxhall tried the plastic tensioner route with the earlier C series engines and got burnt there too yet the Ford Zetec has them and the belt on those is pretty reliable at 100k/7 years, IIRC.

The bottom line is that different engines put these bearings through different levels of punishment as they run at different speeds, tensions and different levels of vibration being transmitted to them through both the mounting to the engine and the running of the belt.

As said, Vauxhall would have dearly loved to halve the frequency of this expensive maintenance task, and they tried twice, so the 40k/4 years rule has been tested well in real life and found to be appropriate.

The V6 never had plastic idlers.

The 4 pot Ecotec does, the early ones suffered failures due to the use of to much glass in the glass loaded nylon so they were brittle.

You will note that they are still plastic but the 'mix' has been changed.

"Cam belt/tensioner life of 4 years. Why?"

Because they are/were a bit crap underengineered.

I always assumed the grease in the bearings dried out after a certain time, usually there is grease evident escaping from the seals, and the bearings themselves only lasted so many revolutions....?

But until we can examine a failure who knows.