Technical Timing Belt/Tension Wheel Query

[mckens02]

Fiat Bravo 1.9 Multi-Jet 150 (2008) Diesel

I'm looking for some opinions on what might have caused my tension wheel to melt/wear down, resulting in timing belt flying off.

The timing belt was replaced three months ago. Car broke down because tension wheel on timing belt melted/wore away, timing belt flew off, wrapping plastic casing of engine. This resulted in the pistons breaking in the cylinder head (due to being out of time).

The mechanic who replaced the timing belt three months ago, sent damaged tension wheel and timing belt to suppliers to investigate. They do not know what might have caused this and take no responsibility. Does anyone know what might be the cause of this happening.

 

[F123C]

Possibly belt tension was set too tight? was there any whining type noise after the last belt change? If belt tension was set too loose, belt could possibly slip on plastic tensioner wheel causing overheating of the plastic but I would expect the belt to jump teeth on the drive gears causing valves to collide with pistons as has happened. After the engine failure was the bearing inside the tensioner wheel seized? Was there any unusual noises from the engine before the timing belt failed?

Regardless of the cause of the failure and damage caused, don't let the mechanic fob you off with excuses - in law, I believe he is responsible for repairing or replacing the engine.The issue of why the tensioner failed is for the mechanic to argue out with his parts suplier or parts manufacturer, its not your problem.

I would suggest you contact the U.K. equivalent of Citizen's Advice or possibly Office of Fair Trading to check what your rights are in the above matter. There's always the option of Small Claims Court once you're sure of your rights.

This is the main reason why I don't do timing belt changes for friends/
family , too easy for things to go disastrously wrong and I would be morally and legally responsible for the necessary repair/replacement of the engine.

Best of luck,
Al.

 

[F123C]

Possibly belt tension was set too tight? was there any whining type noise after the last belt change? If belt tension was set too loose, belt could possibly slip on plastic tensioner wheel causing overheating of the plastic but I would expect the belt to jump teeth on the drive gears causing valves to collide with pistons as has happened. After the engine failure was the bearing inside the tensioner wheel seized? Was there any unusual noises from the engine before the timing belt failed?

Regardless of the cause of the failure and damage caused, don't let the mechanic fob you off with excuses - in law, I believe he is responsible for repairing or replacing the engine.The issue of why the tensioner failed is for the mechanic to argue out with his parts suplier or parts manufacturer, its not your problem.

I would suggest you contact the U.K. equivalent of Citizen's Advice or possibly Office of Fair Trading to check what your rights are in the above matter. There's always the option of Small Claims Court once you're sure of your rights.

This is the main reason why I don't do timing belt changes for friends/
family , too easy for things to go disastrously wrong and I would be morally and legally responsible for the necessary repair/replacement of the engine.

Best of luck,
Al.

Two further thoughts (1): I wonder if the tensioner was renewed when the belt was changed and if a genuine part was used.
(2): You could see if the garage in question is a member of any trade body such as Institute of the Motor Industry (IMI) or SMMT as I think it's called in the U.K. These bodies usually have some sort of an arbitration scheme for customers who fail to get satisfaction when a problem arises and their adjudication is binding on the garage afaik ( I'm not a legal expert!). Of course if the mechanic is a sole trader/someone doing a side job('nixer') or a friend then you probably have no comeback. Best of luck anyway.

Al.

 

[mckens02]

Thanks for quick reply. There was no noise that I noticed coming from engine prior to it breaking.

The mechanic that is fixing it now is the one who put the belt and tension wheel in 3 months ago. He says the tension wheel was at correct tension. He checked the bolt and it was fine.

He did say however that the water pump wasn't working to its full capacity. Could that have caused the tension wheel to melt?

Thanks again

 

[mckens02]

No the bearing was still free/moving afterwards

 

[Freebo]

Did you have the tensioner and waterpump replaces when you had thecambelt done? If so did you use official parts?

Ive known non official parts cause issues in the past, saw someone use a non official waterpump which seized after 2-3 months causing the cambelt to snap and melt causing the catastrophic engine damage.

 

[portland_bill]

What F123C says is all good.

Mechanic is responsible for repairing it. His problem to argue with his supplier.

Tension wheel melting is too much heat, so as F123C says is too tight, slipping, or its bearing seized. Whilst a tight water pump will cause belt shredding and engine failure, it will not cause the tensioner to melt.

Good luck.

 

[mckens02]

Thanks for all your advice and help. Just to be sure, have you ever came across anything that has caused it to melt other than being to tight?

 

[portland_bill]

Tensioner bearing seized.
Tensioner not aligned properly with the belt, causing the belt to rub across its face. That would be a fitting problem and should show diagonal witness marks, unless the melting has destroyed that.

 

[mckens02]

Brilliant. Thanks for your help.

 

[F123C]

Thanks for quick reply. There was no noise that I noticed coming from engine prior to it breaking.

The mechanic that is fixing it now is the one who put the belt and tension wheel in 3 months ago. He says the tension wheel was at correct tension. He checked the bolt and it was fine.

He did say however that the water pump wasn't working to its full capacity. Could that have caused the tension wheel to melt?

Thanks again

I wonder what he meant by ' the water pump wasn't working to full capacity' ? Leaking? play in drive gear? Perhaps he thought the water pump was ok and didn't need to be changed. I think its standard practice to replace the water pump (if driven by the timing belt)at the same time as the timing belt , tensioner plus any guide rollers are being changed. Is this mechanic a sole trader/self-employed? If he works for a garage, is there a service manager/owner you could take the matter up with?

Al.

 

[portland_bill]

I wonder what he meant by ' the water pump wasn't working to full capacity' ?

It is a phrase I have heard quite a few times, but have never understood. Unless pulley or impeller are slipping on their shaft, or impeller has lost blades, the phrase is nonsense. In the event of any of these things, why not just say that instead. it is the cort of rubbish any repairer will say when they are out of their depth. Either way, any fault with the pump may destroy the belt, but won't harm the tensioner. Neither will an overheating engine. Other stuff will fail before the tensioner melts.

 

[F123C]

Tensioner bearing seized.
Tensioner not aligned properly with the belt, causing the belt to rub across its face. That would be a fitting problem and should show diagonal witness marks, unless the melting has destroyed that.

Agree with portland bill above. One other possible cause came to mind, some years ago I heard stories of plastic tensioner wheels or plastic guide wheels becoming loose on their bearings and melting due to the friction caused by slipping on the bearing outer race, can't remember which engine this was on, just throwing it out for possible consideration. It might be helpful if we could see a photo of the damaged tensioner.

Al.

 

[carlorff]

I do not know what kind of proffessinal mechanic doesn't change the water pump while changing timing belt as it is not recommendable but obligatory... unless it is done on purpose to charge it to the customer and keep the rest for himself.

 

[rossocorsa]

I think biggest suspect must be the part itself probably a catastrophic bearing failure or a problem with the way the complete tensioner was constructed. there are lots of poor quality parts out there mostly made in China but they can be supplied by quite reputable after market suppliers, was it a real OE part or one from a proper manufacturer such as skf if not I would be suspicious, even if it apparently was there are companies making very convicing fakes these days too.