Alternator/serpentine
 

Wife’s XC70 had this belt snap/ shredded yesterday. It’s been recovered to he local Volvo specialist- Sheffield and Meredith. We had this changed two and a half years ago and a new tensioner fitted as part of its regular maintenance programme. The car does around twenty thousand miles a year on the motorway mostly. We need it to be reliable in spite,of its 180,000 plus miles. It’s a 2010 vintage. Am I right to be disappointed at this failure? It doesn’t seem a long time? Are these a more regular requirement? It’s probably 50,000 miles it’s run.

As I understand it[could well be thinking of a different engine though]while the timing belt will go for something like 8yrs/100,000mls or so the auxiliary/alternator/serpentine belt is more like 4yrs/45,000mls.If I'm correct then yours would have been due on mileage.

50k is the service interval for the serpentine belt if I'm not wrong

That said it shouldn't have failed on its interval, and there should be a safety margin that would see you far beyond 50k (possibly 100k, but that’s a finger in the air guess, not based on anything but the idea that a 2x safety factor seemed reasonable, and should not be taken as a recommendation but more to reassure that Volvo engineer these things with this in mind and recommend replacement as appropriate) prior to failure,
The most likely explanation from experience is one of the pulleys is providing some extra resistance,
Possibly a clutch or bearing on the way out, enabling the belt to slip, id get every pulley and the attached rotating component's checked and tested prior to refitting a new belt,
Was the replacement belt and tensioner Volvo, I know its cliché but some things that don’t seem to wear well with Patten parts.

TLDR,
More than likely something else is up, the belt failing was a symptom and a straight replacement many not last too long
Rob

I agree, the belt failing was possibly a symptom of a worn bearing after that mileage.

Assuming it is a 5 cylinder diesel it is a complex story . Being 2010 it is right in the middle of a series of recalls and upgrades on the Aux.belt and tensioner .. Yours might have been a hydraulic tensioner which was a recall from Volvo to replace it with a mechanical tensioner .. If you have not seen a dealer since 2010 then it might still be applicable . At the end of all this the Aux belt should be changed every 54000 MILES rather than time .. so it should have been changed at 164000 miles as long as the car has been serviced properly . The cambelt and tensioners are changed every 108000 miles when the Aux belt and tensioner are changed too . Hopefully your engine isn't wrecked , It could well be if the broken belt has tangled with the cambelt ....

Collected the car this morning from Sheffield and Meredith.
He said I was lucky it hadn’t taken out the cam belt or anything else when it went. Simply snapped/ shredded itself.
The car had new belt and tensioner two and a half years ago. They told me that Volvo have now apparently recognised a problem with the belts being prone to weakness and had developed a new stronger belt they now supply.They only buy these belts to fit now as the car supply places don’t guarantee a new stronger belt. Just under ninety quid fitted and back on the road before lunch and I’m ok with it.
So be aware there is a newer stronger belt available from Volvo and the old ones must now be considered prone to failure.

I have read many times about the tensioner problems, belts breaking and so on. Did a lot of research on just this subject after I bought my car as it supposedly came with a timing belt change. A little digging showed the belt was the only thing that could be verifiably judged as being new. So I had the whole lot done again, belts and tensioners. In all the reading I have done on this forum and others I have never heard of a stronger belt. Maybe I just missed this info or maybe it is because my car is 2008.

It's longer not stronger due to the conversion from Hydraulic tensioner to the original Mechanical tensioner., The service interval was reduced to 54000 miles from 108000 miles as it gets a lot of sharp tugs when the engine initially fires , that is when it can break around 70000 miles . It is nowhere near as strong as the earlier Aux belts used on Volvo engines which could go the full 108000 +++++ miles . .

I know the belt has to be changed every 54,000 miles, but if the belt and tensioner were changed to the new mechanical type, does the tensioner then need to be changed at every 54k belt change or does the mechanical one last longer?

Only the Aux.belt is on the schedule to be changed at 54000 miles , The tensioner is changed with the cambelt every 108000 miles ..