Aftermarket cam tensioners

[MikkiJayne]

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?

[Goran]

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)

[MikkiJayne]

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

[MikkiJayne]

So this is interesting:



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"

[Architex_mA8tey]

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

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