Aftermarket cam tensioners
 

Hi all,

Has anyone used the aftermarket cam tensioners for the 40V? I just got a price of £478 from TPS which is totally untenable, and unfortunately our hosts don't have any used ones at the moment.

Background - lumpy idle, CEL for cam position sensor, compression 10-11 bar on 1-4, 12-13 bar on 5-8. Opened up the cam covers to see the 1-4 bank tensioner jumping up and down when I rotate the engine by hand. Seems that the top of the tensioner is loose and the bottom is locked solid so the chain is slack and the inlet cam is jumping around.

Very :-( at the moment. I don't want to spend £1000 on tensioners to find there's valve damage, but very wary of putting potentially crappy Chinese bits inside the engine.

Thanks
MJ

My advice would be to go oem regardless of cost.
Yes, a8's are expensive to own.

Also, get it checked out by an expert to be sure if its the tensioner and which part of it thats faulty. I'm not sure you can determine faulty operation in the way you describe. There is a solenoid which is a part of the tensioner mechanism and this has no power going to it when you are rotating the engine by hand.

At least, follow the ElsaWin audi workshop fault guide for the tensioner to test it in the correct way.

IIRC without the engine running the chain will be slack anyway, the tensioners need oil pressure which requires a running engine.

Do you get any constant rattling from the camchain area when the engine is running, do the tensioner pads show any sign of wear or failure visually?

My take on aftermarket parts

They don't always fit correctly, they don't work as effectively as original parts, they don't last the test of time

Thanks for the thoughts guys. I'm comparing the two banks to conclude it's faulty. Turning it over by hand the chain for 5-8 is taut on the tensioner and the cams turn smoothly. 1-4 however the tensioner jumps up way higher than the other one as the inlet is about open a cylinder, then as soon as it's past centre the cam jumps round off the rollers and the tensioner drops down.

This is what I found when starting to investigate the cam position sensor error:

http://www.corradov8.com/pics/ohfck.jpg

Timing belt changed without the damper :mad: Tightening the belt and setting the cams with the bar I get bank 1 is about 2 bar short on compression compared to bank 2. I'm really hoping its this dodgy tensioner causing the lost compression rather than many bent valves.

I also discovered that the impeller has fallen off the crappy aftermarket water pump and started machining its way in to the block. Temperature was fine on the drive home from picking it up though (and it drove fine apart from a vibration at idle and an occasional misfire) so I'm hoping a new pump will be ok.

If it was just the tensioner then I'd buy a genuine one without question, but with the engine potentially fubar I'm not going to spend that on it until I know the engine is still ok. I think I'm going to put an ebay tensioner on it to start with to see if it runs properly and then change it out for a genuine one if the engine is ok. That way I've only wasted £100 and some time, rather than £500 if its toast.

In case anyone recognises the stupid orange pulley, yes this is the one from ebay. I bought it based on VCDS saying the cam position sensor was open circuit and it driving fine. No idea it was potentially going to need a whole new engine :mad: Bent valves would actually have been cheaper. Stupid stupid stupid.

Oh, and to add insult to injury, the really tricky bolt for the oil cooler under the manifold is totally rounded out so I've got to take the whole damn engine out to change the plastic pipe. Hard to convey how fed up I am with this car already. I've been looking forward to getting another D2 for ages but I'd have been better off just setting the cash on fire.

If your parts are coming from TPS do they not meet VAG spec?

Could it have jumped a tooth on one of the cams

Rather surprisingly it didn't jump a tooth at all - when I pulled the tensioner tight and locked the crank the cam bar was just a mm or two off fitting in place. The belt had been fitted by marking the pulleys rather than using the proper tools. Its amazing its not completely destroyed tbh. POs have been driving like that for up to 5000 miles since the belt was done.

I've got a £100 ebay tensioner on the way to test. If I get compression on 1-4 with that in place (and the cam stops jumping about) then I'll spend the £500 on a genuine one from TPS. If the valves are bent or there is other internal damage then I'll be looking for another engine and I've only wasted £100 instead of £500. The engine is out now anyway, since its utterly impossible to get to that rounded off oil cooler bolt with it in the car. I'm going to do a complete re-seal on everything and clean up the bay while its out, and I can compression test it on the floor.

This car is like a mistreated horse - its now kicking the crap out of anyone who comes in range :(

I hope its just the tensioner and is easy to fix, they are lovely cars when in good working order.

If you haven't got one already, one of these cheap little cameras should fit down the sparkplug hole may have enough resolution to confirm any contact marks on pistons.

Also worth scanning with VCDS to see what error codes come up, and to see if its recording any actual missfires.

http://www.ebay.co.uk/itm/USB-Waterp...cAAOSw~gRV1BSs

http://www.ebay.co.uk/itm/2m-High-Re...8AAOSwFnFV~21H

Let me know if you want ElsaWin instructions for tensioner testing, I can easily copy it to PDF

Ooh thats a good idea - I've got one of those for drains. I'll have a look tomorrow. I have Elsawin thanks :) I love how the tensioner procedure starts with "Remove engine" :rolleyes:

When I picked it up it was just showing Cam pos sensor G40 open or short, and that came straight back after clearing everything. By the time I got home we also had:

Fuel Trim bank 1 too rich
Multiple cylinder misfire
Cylinder 5 misfire
Cylinder 8 misfire
Cylinder 7 misfire

G40 is the one on bank 1 afaik - that makes sense, as does the fuel trim. The misfires on bank 2 seem a little odd, but then the cam belt was flapping about all over the place so who knows what bank 2 was doing. Interestingly the misfires only happened on light throttle. Give it a bootfull and it was fine - scary now to think that it could have skipped one or many teeth at any moment :eek2:

Here's an interesting shot of the tensioner. Pretty sure there should be a filter in the oil feed hole but it's nowhere to be seen. Given that the klutz who did the cam cover gaskets glooped the hell out of everything with some sort of evil silicone it wouldn't surprise me if the tensioner is blocked with some of it.

http://www.corradov8.com/pics/tensioner1.jpg

Here's another pic of how high it was riding when the cam jumps about:

http://www.corradov8.com/pics/tensioner2.jpg

The other one doesn't allow the chain to go higher than the two ears whereas this one just flaps about. I'm going to clean all the goop out of the engine so I'll have a look at the other one to see if that still has it's filter. At least I can nick the one from the ebay special if it's missing! The bottom shoe is locked solid btw - no idea if thats normal or not. I've dealt with engines which have these before, but never had cause to remove one til now.

Since I've had this thing in front of me I've been thinking about what Mannyo said about oil pressure. Looking at it, it seems that the top shoe is a lightly-spring sprung tensioner which is backed up by oil pressure, and the bottom shoe is the one used to vary the timing by moving the whole assembly up and down.

Looking at pics of new ones, the bottom shoe on mine appears to be in the correct location, so now I'm puzzled why it seemed to be so slack, but more specifically, why the other bank isn't slack? The chains are the same side to side so why the different behaviour?

I was thinking perhaps an oil retention valve had failed on bank 1 and so was letting pressure out of the tensioner, but in that case why would it be sitting so high on bank 1 compared to bank 2? Surely it would be the other way round?

Also, when I've been compression testing the engine has been spinning long enough that it should have oil pressure so should have pumped up the tensioner. Perhaps there is indeed silicone inside it blocking it up?

Does anyone have a pic of how both of them look in a working engine please?

The nylon sliding shoes look very un-worn on that tensioner. It could be the light but the colour of them looks slightly different to the original shoes that came out of my S8 at around 110k miles.

How does the chain wear track compare between the faulty tensioner and the working one? Also pad colour the same?
Just wondering on the off chance its a non-OEM tensioner. Or maybe just the shoes were swapped.

Definitely missing a small fine-mesh filter in that oblong hole.

I forgot how the mechanism works exactly, there is a locking pin somewhere that is released by oil pressure, it could be the lower pad that's locked until oil pressure releases it. There is a 40V engine study guide somewhere perhaps on a sticky.
Both my old tensioners are locked on the bottom pad, free moving top tensioner on a spring, they were working when replaced (replaced preventatively)

Yeah they're barely worn at all. The other one is exactly the same - 110k on this one too. Are they less worn than yours?

I'm pretty sure they are original - proper markings etc, and externally they look the same age as the engine. Its my phone camera that makes the shoes look a different colour I think. They are a brown colour like builder's tea, rather than the greyish they appear in the pic.

I just popped the cam covers off a 30V V6 I have in the workshop to compare, and that exhibits exactly the same behaviour as bank 1 - the tensioners jump up and down when rotated by hand. That engine definitely has no oil pressure as it's been sitting for a few years.

So, the plot thickens... maybe the tensioner is a red herring and in fact it is an oil pressure thing? I'm very curious about why the two sides appear to have been behaving differently. I'm doubting myself now, wondering if I've suffered from 'direction of fit error', looking for a problem on bank 1 and not noticing that 2 was behaving the same.

I had a look in the cylinders with my camera - it'll resolve the carbon on the top of the piston, but only when the piston is at the bottom of the bore. I can't do that with the cams out and belt off so I'll have to put it back together and time it up again and have a look at each pot one at a time. I think thats now going to be what determines whether the heads come off since the compression test appears to be somewhat misleading...

I'll have a look for that SSP too :)

So this is interesting:

http://www.corradov8.com/pics/tensioner_diag.jpg

This suggests that the bank 2 tensioner is actually upside down compared to bank 1, and the sprung part is underneath (unlike the V6 where they are both spring-side on the top). That would mean that the behaviour I was observing is in fact correct, although that seems very odd to be different to the V6 when the two engines share so much in common.

I'll pull the bank 2 tensioner later to have a look, since its got to come out to clean off the silicone gloop and check for the gauze filter.

I should probably change the thread title to "Should have read the SSP first" :o

the SSP you seek is 4th from the bottom on this page -

http://forum.a8parts.co.uk/showthread.php?t=9345

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