Audi A6 3litre quattro - Cam/timing belt failure - worried345

The cam belt on this car has just failed, 10,000 mile before the recommended cam belt change every 80,000 miles. it has been serviced according to Audi's requriements (extended service intervals advised by car's computer)

3 weeks previously the alternator seized with the alternator belt snapping, could this have damaged or weakened the cam belt, and should the garage who replaced the alternator and alternator belt checked the cam belt for possible problems as a result?

Audi A6 3litre quattro - Cam/timing belt failure - injection doc

awkard situation !

Has anyone dismantled the car yet to discover why the belt failed ? it is remotley possible that fragments of alternator belt found their way into the cam belt cover ! I think you need a total inspection independantly, but may have to accept the situation for what it is.Has it always been serviced by Audi ? have you spoken to Audi customer service ?

Audi A6 3litre quattro - Cam/timing belt failure - John F

Sorry to hear of this, but very interesting as I have a 1998 A6 2.8 with presumably much the same belt layout. There is no way bits could access the cambelt area without breaking through the cam covers. This is the first time in any forum I have heard of an Audi V6 cambelt failure - probably because it is less stressed than the ubiquitous 4cyl 1.8

What year is it? Is it just coming up to 80,000, 160,000 or 240,000? or more?!

I inspect my cambelt every 10,000 or so. It's the original, and at 114,000 looks and feels strong enough to drive a motorbike's rear wheel, let alone the short puny little camshafts it actually drives. Despite your story I have no intention of changing it.

Audi A6 3litre quattro - Cam/timing belt failure - Peter D

When was the cam belt chanced last month and year and the mileage. Regards Peter

Audi A6 3litre quattro - Cam/timing belt failure - Roly93

inspect my cambelt every 10,000 or so. It's the original, and at 114,000 looks and feels strong enough to drive a motorbike's rear wheel, let alone the short puny little camshafts it actually drives. Despite your story I have no intention of changing it.

Dangerous tactic ! You cannot really tell the condition of a cam belt by looking at it. Okay if it looks rough with teeth worn away, dont re-start the engine and change immediately. However it may look like new and fail due to internal fatigue.

Audi A6 3litre quattro - Cam/timing belt failure - John F

Despite your story I have no intention of changing it.

Dangerous tactic ! You cannot really tell the condition of a cam belt by looking at it. Okay if it looks rough with teeth worn away, dont re-start the engine and change immediately. However it may look like new and fail due to internal fatigue.

'Internal fatigue'??? Please provide evidence. As far as I know it behaves neither like metal nor like the royal mail's rubber bands. Please provide age/tensile strength charts. Certainly the one fitted to my car looks amazingly overengineered. I would think it might last longer and stretch less than the tiny bicycle chains fitted to the VW/Audi 'W' engines.

Audi A6 3litre quattro - Cam/timing belt failure - Roly93

'Internal fatigue'??? Please provide evidence. As far as I know it behaves neither like metal nor like the royal mail's rubber bands. Please provide age/tensile strength charts. Certainly the one fitted to my car looks amazingly overengineered. I would think it might last longer and stretch less than the tiny bicycle chains fitted to the VW/Audi 'W' engines.

As I understand it whether a belt will break is not just down to physical wear, it is also down to heat-cold cycles of the materials used in the belts construction. ie Staring the car at -10 and running the engine temp up to nearly 100 degrees for instance. I maintain that unless you near-microscopically inspect every bit of the length of the belt you can't be sure it still has good integrity. Sure the belt on my Audi looks over-engineered and I dont do too many stop-start journeys, but I still wouldn't take the risk of exceeediong the stated change interval just based on a quick look at it.

I have seen a cam belt that had been broken, and to be honest the rest of it looked okay.

Audi A6 3litre quattro - Cam/timing belt failure - John F

I have seen a cam belt that had been broken, and to be honest the rest of it looked okay.

I don't think the temperature variation is much of an issue in our temperate climate, Roly; I can't imagine how it would cause the belt to deteriorate. I would lay odds that the cambelt you saw had been broken by an unusual stress, e.g. failed bearing of driven pump/alternator or tension pulley failure.

I have been carrying a spare fanbelt in my TR7 for 30yrs. The original item, a flimsy toothed 1cm wide band, shows no sign of deterioration yet. I suspect my Audi cambelt is made of sterner stuff!! I would be much more concerned at having the original belt replaced badly with an inferior product....there are too many stories of belts failing about 20,000 miles after their conscientious owners had replaced them 'for peace of mind'.

Audi A6 3litre quattro - Cam/timing belt failure - madf
I don't think the temperature variation is much of an issue in our temperate climate, Roly; I can't imagine how it would cause the belt to deteriorate. I would lay odds that the cambelt you saw had been broken by an unusual stress, e.g. failed bearing of driven pump/alternator or tension pulley failure.

I have been carrying a spare fanbelt in my TR7 for 30yrs. The original item, a flimsy toothed 1cm wide band, shows no sign of deterioration yet. I suspect my Audi cambelt is made of sterner stuff!! I would be much more concerned at having the original belt replaced badly with an inferior product....there are too many stories of belts failing about 20,000 miles after their conscientious owners had replaced them 'for peace of mind'.

Climate is immaterial when underbonnet temperatures can exceed 100C with a turbo in full throttle.

Modern cambelts are subject to far greater stresses due to often running oil pumps/water pumps and various pulleys. Rapid changes of speed put huge strains on the fabric - acceleration/deceleration.

I have seen piccies of a Lexus 2 litre cambelt which looked fine from the front but the rear half did not exist due to a faulty tensioner... There were no sounds or external signs of problems...

Most cambelt failures after replacement can - in my view - be attributed to non replacement of othet items driven by the cambelt.. Specifically water pumps (VAG) or tensioners which have a finite life almost the same as the cambelt. Fra more likely cause than inferior products.

Malfitting is also an issue.. either non aligned correctly or belt stretched during fitting..

Judging by the standards of many mechanics, I would trust few...

Audi A6 3litre quattro - Cam/timing belt failure - SteveLee

Are you sure it's the belt that's failed? This engine has been known to eat the odd lifter leading to camshaft failure or snapped/slipped belts when the cam hits the immovable lifter. (PS don't confuse with the V8s where the chilled-on cam lobes slip on the shaft wrecking the engine) Vorsprung durch Technik - as they say in Germany.

Audi A6 3litre quattro - Cam/timing belt failure - John F

This engine has been known to eat the odd lifter leading to camshaft failure or snapped/slipped belts when the cam hits the immovable lifter. (PS don't confuse with the V8s where the chilled-on cam lobes slip on the shaft wrecking the engine)

This is an interesting post, Steve. How does it 'eat' a lifter? I thought the non-adjustable hydraulic tappets were in constant contact with lobe. And are the lobes of the V8 camshaft really just slid onto the shaft and frozen into place?

All the sites I've come across, both UK and US, seem to agree these 5valve V6s are both reliable and long lived.

 

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