Timing chain problems

[Goran]

I'm really glad you got it sorted and that the engine wasnt a write-off.
Sorry to hear you have another noise, hope its sorted out soon.
I was just wondering did they use the plastic because the chain runs over it? If they used aluminium instead would that have been a bad idea, ie, lots of aluminium particles in the engine bay and wear on the chain from rubbing?

I have been looking up BMW V8 engines and it appears they have these plastic variators/tensioners too, in addition to VANOS, only American V8's like LS2 appear not to have such plastic things in the engine.

[Mr K]

I dont think the problem is the plastic shoe, but the small tensioner that presses on the shoe. in theory the ram will always provide a constant tension, and therefore take up any slack generated from the wear of the plastic part. The problem comes when the tensioned doesnt provide a contant pressure, presumeably due to the O ring breaking down?

[ulfilias]

@Mr K

No....The origional issue was a worn tensioner and a broken shoe. Those bits of plastic after the shoe has fractured are not good and once the shoe dies the chain wears a nice big groove into the metal that supports the shoe, killing the tensioner !

I now have a second issue in that my drivers side tensioner is acting strangely. Instead of a light flutter of minor timing adjustments (which it does when cool) it is going from fully retracted to fully extended and making a nasty clunking sound (orgionaly thought as gear box).

It could be a fragged tensioner again (Arse. Front end off, £360 part, best part of a grand as the timing belt needs re-doing to access the cam). However it looks like it *IS* working, just over adjusting. There is a timing sensor error too....So am wondering if it is the sensor that is giving the wrong info, or the tensioner that is working wrongly. Could also be the solinoid on the tensioner, which is easy to change and i have a spare.

Any other ideas ???

Ta,
Lee

[ulfilias]

Alas the sensor and solinoid hasn't worked.

The variator is rising and falling, very methodicaly but to the extreams of its travel. Any idea on why.....I am loathed to swap it out without knowing its broken and the fact it is moving leads me to think it is something else !

Ta,
Lee

[Just_Ben]

If the tensioner is moving fully in and out then it's probably knackered and holding no pressure it will be being pulled in and then out by the chain tension changin from top to bottom as the cams rotate. As the cams open valves they resist rotation and when the valves shut their springs help rotate the cams and so this takes the strain off the chain. This has the effcet of moving tension from the top to the bottom of the chain - try rotating the engine with the cam covers off by hand and you'll see it happen as the cams flick round as the valves shut!

[ulfilias]

It doesn't appear to happen when the engine is cold....It takes a few minutes to warm up and start banging. Initialy it flutters as expected.

[SyncroS8]

Any update on what the problem was with this?

Thanks

MG

[Goran]

Hi Synchro,

check out this forum in the States, he had the engine running with cam covers off so he could see what was going on.

http://forums.quattroworld.com/a8/msgs/66027.phtml

thats after he replaced the pads on one side:

http://forums.quattroworld.com/a8/msgs/55496.phtml

German engineering. Very clever but over complicated.
You should have got yourself a LS2 or LS3 V8 for your project, there are adaptor plates available to fit it to a Porche or Audi 01E gearbox.

[SyncroS8]

Hi Gorhan,

Thanks for the links... very useful

I would have an American engine but none of my tools will fit it

Only kidding. I'm fairly into my German cars.

I've been slowly replacing parts to get my engine to be as quiet (and happy) as possible.

Now that I've replaced noisy alternator bearings and tensioners, I can hear the rest of the engine enough to know that there's a little bit of noise from the chains. Not enough for me to think that any of the pads have gone walk about but I'm interested to read about the locking pins which fail.

I'll be pulling the cam covers off tonight just to confirm my thoughts.

MG

[Goran]

I shouldnt be unfair to German engines, they are pretty great .
If you do open up the covers please take a picture or two.
I too want to replace those pads as soon as possible, even though theres no chain noise (I only had a couple of seconds of chain noise only during start up in winter, but apparently this is normal).