3.0 V6 TDI timing chain broken - repair or sell car as is?

[AndiB]

2009 A6 3.0 TDI Quattro 110,000 miles.
One cam is not rotating due to broken timing chain. Engine in car still. Garage unsure of the labour or work involved. We don't yet know whether there is piston or head damage.

Any experience of this? Any idea of the labour involved in engine out, investigate and then replace chain and if necessary fix the head?

Also I thought chains were meant to last. Why might it have broken?

I have owned the car from new, and always serviced on time with Audi for two years and trusted independent in following seven years.

This is our main car

Any advice much appreciated.

Thanks

[AndiB]

Thanks all for your help and comments.

So I now have my car back fixed. The cause of the problem was a broken top timing chain. I will put some notes below for the benefit of others in the future.

The engine has four chains. One of which go to each over head cam. A common failure mode is for the top chain tensioner (which is hydraulic) to wear and the chain slap around, especially at start up when the oil is cold, and it to jump a sprocket or more causing bad timing. The ECU then refuses to work due to the timing problem. I was told that if it has jumped perhaps 4 or 5 teeth or less then there will probably be no damage to the head. Resolution would be to replace the top tensioner (or both as a precaution) which can in fact be done with the engine in the car and reset the timing.

In my case the chain had actually broken. It was engine out, replace top two and two tensioners, head off, check valves. The head was ok. The chain had failed with the roller disintegrating off the link pin. Perhaps these bits caused the chain to snap or not. Gearbox and sump came to look for the roll but it could not be found so is presumed to have left with last oil change. There was no sign of excess heat or poor lubrication. The garage said they rarely see failed top chains and have never seen a bottom chain go.

In total 25 hours labour, two chains and top tensionsers, head checked, head bolts, misc gaskets and cv boot, air con recharge, oil, filter, coolant, vehicle relocation... 3k inc VAT.

For me it made sense to repair as I have had the car since new and without repair it was effectively worthless.

btw. there was no significant noise heard before the chain broke as you might have heard if it had been a tensioner failure and the chain was slapping the cover.

I hope this helps someone in the future.

Andy

[AndiB]

I used Audi Specialists in Burwell near Cambridge. The main guy there is called Andy

Good luck.

[AndiB]

Engine stopped suddenly.

[AndiB]

Noise is probably the pistons slamming into the valves. Depends on the engine and the position of the valves when the chain broke as to whether the valves are sticking out into the way of the piston.

No, it’s not going to start.

Costly. Good luck