mmthorn

[QUOTE=Sverige;25055624]It was hard to see what was happening on the previous video from overhead, so this morning I've filmed the tensioner itself (and you can see the corner of the intake sprocket too). One complete revolution of the engine was made and in that time the tensioner piston went in and out, three times collapsing down part way with a "pop" sound. Is this right? Is it a problem and any ideas why it is doing this?

i thought about chain pretensioning as a cause, but if that was the case wouldn't it go loose for half a revolution then tight the other half revolution? Not loose, tight, loose, tight, loose, tight 3 times per engine cycle?

/QUOTE]
I haven't done the job yet but getting ready to.

CYNMAN wrote this on 11/26/14.

"#5 When you get the new tensioners installed and you are spinning the motor over 720 degrees to check to see if the cams remain in time and come back to the locked position, get someone to help turn the motor while you watch the cams move. They will make a snapping sound as the lobes clear the valves but this is normal. If the cams snap and then stay stationary, stop turning the engine as this means they likely skipped a tooth on the drive gear. You will now have to remove the cam adjusters and reinstall the tensioner. Most likely, you didn't follow #3 above and the spring tension was not enough to keep the chain tight. When I followed the procedure outlined in #3, the tension held."

Sverige

Thanks Mmthorn- are you quoting that because you think the lower sprocket is skipping in video, or because it says the snapping sound is normal? My engine stays in time after a complete revolution, so I thought this meant there was no skipping happening.

What im hoping to establish is whether the tensioner popping back in like this is somehow normal or if it represents a problem, and if it's a problem then why it might be doing this so I can fix it. I'd appreciate any insight.

mmthorn

I am referencing that the snapping sound is normal. Others in the forum have also mentioned the snapping sound. I appreciate how careful and methodical you are approaching this. I have started the procedure and will probably be installing tensioners in another week or so. I will rotate my engine before I remove the old bank2 tensioner and let you know if it "Snaps"....probably can do this tonight or tomorrow.

Sverige

Thanks mmthorn, I appreciate that. Please review my videos and note the way the tensioner piston partly closes and the chain tension at the tensioner arm is released at the same time the snap sound is heard. What would be awesome, if you have the chance to hand crank your engine before disassembly, is if you could observe your tensioner's piston to see if you also see it part-closing each time there is a snap sound. This would then confirm that it's the normal behaviour, strange though it seems.

If you would find it possible to record video from the overhead position similar to my video here, that would be the best possible comparative resource, but I appreciate that might not be so easy so please don't feel obliged to do so.

mmthorn

Here are the videos of my cam chain and presumably failed tensioner piston. These videos were taken prior to me removing the tensioners and just a few days after shutting the engine off (i.e. still had oil in tensioner piston). You can see that the piston moves in and out and I think actually gets worse the more I rotate the engine. It also looks like the piston is leaking (whether or not this is by design or not I don't know). When I first removed the rear cam cover the chain was tight. After a few rotations the chain has become loose. I think it's obvious that the pressure is dropping given that the oil pump is not supplying oil to the tensioner piston. I now have the cams locked and will be putting the crank pin in place. Looking forward to putting a new tensioner assembly in the car and buttoning back up. Starting to get cold out and expecting snow this weekend.

Sverige

Hi mmthorn, thanks so much for your videos and input - I agree with your analysis. I'll get mine put back together but you may heat me as I won't have time to do anything until the weekend. Will be interesting if your new tensioner makes the same clicking sound as mine.

i suspect the oil coming from your piston indicates it needed swapping out due to failed seal, so even if it doesn't resolve your engine codes it will have been worthwhile.

Good luck swapping your tensioner and watch out for the bolt under the chain - you have to pull the chain aside a little to get to it, then it would be so easy to drop it if it catches on the chain as you remove / refit the bolt.

LarryJa

Sverige,
It sounds like you had gained reassurance that the snapping was typical.
Have you started your engine up yet?
If so, how long did it run before it was normally quiet? I would expect it to quiet as oil pressue came up.
Let us know your status. I'm sure that thete are plenty who are most interested to hear it.

Sverige

Hi Larry

yes, I was satisfied that the snapping sound was normal behaviour so went ahead with getting the car back together. On first startup there was a brief rattle which quickly went away as the oil pressure built, and I was able to observe block 93 values on bank 2 of 0.0KW intake and -0.4KW on exhaust. Soon though, after perhaps 30-40 seconds a rattle sound began which became louder, so I switched off the engine. On restarting the engine sounded good again but after the same period of time it started rattling.

I retired to think things over and returned the next day and when starting the car found it rattled loudly right from the start. On the 4th startup it began quietly then started rattling after around 30 seconds.

Enough then - it's clear the new tensioner has failed for some reason and I'm just awaiting the return of enough mental strength to dive back into getting it taken apart to see what is going on under the timing chain cover. I am wondering whether the tensioner gasket has not sealed correctly, or maybe the chain tension was wrong or the new tensioner was simply faulty.

LarryJa

Sverige,
That's unfortunate, after all of your research & cautious efforts.
However, it will be very informative to follow your contining work to solve your 3.2's issue. I am certain that you will persue it to a sucessful end.
BTW: is the replacement tensioner a genuine audi part, or an eBay/chinese replacement?
Keep it up!

Sverige

It is a genuine Audi tensioner. Now removed from car and the piston will not pop out however much I compress it. I guess I have to source a new tensioner and try fitting that, but still not 100% sure if the backplate didn't seal properly or I messed up pretensioning the chain.