A while ago I asked for any actual experiences of belt/tensioner failure on these cars. Here's a reminder of one reply....
"Author: Neil (---.sunderland.ac.uk) Date: 14-06-01 15:45
My wife and I drove a Fiat Bravo for three years (80000 miles). The belt and tensioners are designed to last 72000 miles.
The original belt was replaced under warranty due to worrying noises from the engine bay at 36000 miles.
The second belt snapped at 70000 miles (after 34000 miles of use) resulting in a bill for almost £1000."
On the Car by Car breakdown HJ mentions...
"Plastic timing belt tensioner pulley can shatter without warning. Best to change timing belt and tensioner every 3 years/35,000 miles."
Well finally I have pushed the customer into a timing belt and tensioner pulley change at 44,000 miles. Doing the job yesterday I had real concerns about the design of this setup.
As expected the old tensioner/pulley had a plastic gear, which was in OK condition (that doesn't mean it wasn't going to shatter tomorrow), but I was amazed the new one from Fiat was the same with no change of design/part no./materials. Odd if it has given trouble.
Many belt tensioners are moved to the correct tension position by whatever method and then the mounting nut is tightened. This means the tension is set for the life of the belt. The reality is that, as the belt wears with age, the tension gets less over the life of the belt. Some belts at/over the due mileage have a frightening amount of slack.
Now this Fiat has a tensioner that is moved to a set position then has a spring to take up the last bit. In running this spring allows the tensioner pulley to move a fair bit with an alarming whip to the belt. The result of this on the car I have here is that the old belt has already worn halfway through the plastic lower timing belt cover (where the whipping has thrown it out of line) and the back of the belt is damaged from this constant rubbing.
I do wonder if it isn't just the plastic pulley breaking but also this whipping movement that is leading to failure. If it was my own car I would modify the tensioner pulley mounting to give a rigid tensioned setting. But with the customers all I can do is fit the correct Fiat parts to the Fiat methods and not worry further.
David
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Share your concerns, David. The best solution should be a spring or oil-pressure tensioned jockey pulley. Timing chains are often so arranged. An oil-pressured tensioner in a non oil-selaed area would be trickey, but a spring arrangement should not be difficult, but it would seem that on the car in question the spring tension is poor.
I try to encourage my customers to call me back after 1,000 to check & adjust belt tension, but all too often I never get the call !
Time and again I comment on the classic sound of a belt slapping the inside of the cover, only to be told that it has "only just been replaced". The noise often dissappears once warm, so the owner ignores it. AT THEIR PERIL !!
Regards, Adam
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Surely some sort of spring adjusting mechanism to aid initial tensioning when replacing the belt would be sensible. See the setup on the Rover K series engine. Simple and reliable.
If a belt relies upon spring tension to keep it 'on track' whilst running, I would be worried about durabilty.
Adam, surely, you're not going to go to all the trouble of checking/adjusting the belt tension after 1K? Getting to the tensioner on some engines is a nightmare!
Rgds
David
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David,
I know what you are saying, and certainly I don't find it necessary on all engines, but CVH Fords and single-cam Vauxhalls (using manufacturer's or Gates belts) do seem to go slack very quickly sometimes. I always run the engine for at least 15mins with the covers off and re-check the tension before re-assembly, but even then when an owner does let me go back after a few weeks there is often scope for re-tensioning again.
Regards, Adam
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Yes, Adam I agree - running the engine for 20 mins or so with the covers off to bed the belt in is a good idea - and have done so many a time before. I certainally would do this with my own motor, without fail.
Perhaps this could be the reason we see so many belt failures - incorrect tensioning - and not always the fitters fault, either.
The worst offender for shredding their belt(s) has to be the 1.8 dog-of-a-diesel Ford motor and the Ecotec 16V Vauxhall engine, agree?
Rgds
David
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The other belts that need to be re-tensioned after 1,000 miles or so are the pair that drive the cam shafts and balancer shaft in the Porsche 944 engine. There was a cambelt failure on 'Deals on Wheels' tonight. On an Escort RS2000. They showed us the broken belt. Looked very much like a chain to me, as fitted to the old twin-cam 2.0 litre Ford engine. Rest of the programme was really good though. Especially the bt where Mike tried to trick a couple of amateur 'experts' and they sussed every single one.
HJ
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