VR6 Rattling noise : Pinking or cam chain?

[briggy 0]

Hi,

 

I have a VR6 with 107,000 miles on the clock.

 

When I put my foot down at about 3000 rpm, I get a rattling noise, like ball bearings in a plastic cup. I'm told that this may be pinking and that it's bad news. One suggestion was to use a higher octane fuel, so I've switched to Optimax. The noise hardly ever occurs now, bit still does the odd time.

 

I've also heard that the cam chain tensioners can go at about 100,000 miles and from reading the forum, the noise is quite similar. As far as I know, these have never been changed. I know all about the damage a broken cam chain can do.

 

I'm not particularly experienced mechanically, but don't mind getting my hands dirty. How do I spot tensioner damage - i.e. where is it and what does it look like?

 

Cheers,

Bryan

[Supercharged 2]

What year is your VR? I would get it VAG.Com'd first off to find out if there are any engine sensors not working and causing it to pink...

 

To inspect the upper tensioner you will need to take the valve cover off which is underneath the inlet manifold, the chains are on the gearbox side of the engine

[dr_mat 0]

Do you have a VGI/VSR fitted? It's odd to get pinking at 3k rpm on a standard engine, whatever the mileage. It's equally odd to hear timing chain rattle (definitely not the same type of noise) at 3k rpm - usually timing chain rattle is most audible at around 1200rpm and quietens right down above 2-3k.

The fact that it only occurs periodically, and that it goes away with better fuel, suggests that you're more likely to have an engine sensor out than timing chain probs (well - you may well have timing chain probs ASWELL, but that's not what you're describing here)...

Quite likely a bad knock sensor, or MAF sensor possibly.

Get the ECU scanned for errors - that's your first port of call..

Second- talk to Roger Blassberg on here he had similar and it turned out to be a dodgy knock sensor.

[Roger Blassberg 0]

Briggy,

Pinking is an irregular very high pitched clatter which usually occurs when accelerating hard from quite low revs, especially when the engine is hot. Timing chain rattle is a different noise, but, admittedly similar, but generally of a lower pitch and coming very spcifically from the gearbox end. I think the way to tell one from the other is this - if the chains are rattling they will do so with the engine off-load (ie out of gear, sitting on your driveway) and particularly at 1200-1500 rpm. Pinking will not occur under these circumstances, only under load and over a wider rev range.

 

Pinking was a problem with mine until I had both knock sensors replaced. They are relatively expensive - about £125 for the pair (one front of the block, one back.) The real problem is getting at the front one as it is thoroughly buried under the inlet manifold, which needs to come off to get at the sensor. Make certain that the through-bolt on each sensor is done up to precisely the correct torque of 15 lbf-ft, or they don't work properly. Too loose - no signal, too tight and you wreck it. Also, the contact surface with the block must be scrupulously clean. VAGCOM will detect a discontinuity in the wiring but not a damaged or partially inoperative sensor, a loose bolt or a poor contact surface.

 

If using Optimax has made the problem less frequent, maybe it is pinking; but the knock sensors should be able to cut out pinking even if you are using 95 octane, so maybe they are not working as well as they should.

 

Come back to me if there are further questions.

 

Best wishes

 

RB