cam chain tensioner shoe - can it be improved? - Page 4

27litres · #31 25th December 2016, 12:47 PM

+1 on pics please Mikki.

Goran's photos seemed to confirm that MRC didn't remove the intake cam during pad replacement and therefore used the 'chain wiggle method'.
Certainly explains the 4 hours labour...

MikkiJayne · #32 27th December 2016, 10:54 AM

I had a quick look at this to see if its worth coming over to have a try, and I think not unfortunately.

I did contrive a way to compress the tensioner without 3366 so it might be feasible to do the top pad, but no way are you getting to the bottom one without taking the tensioner out

This is from the FE with 113K on it by the way! I'm actually inclined to suggest doing these every 80K when the timing belt is done, after all you're halfway there with the belt off anyway. That little bit of schmutz on the top of the pad isn't dirt btw - its the plastic breaking up. Its really s****y quality plastic to have bubbles in it like that

If it were solid it'd probably last much longer, but as it is it looks like as soon as the chain breaks the smooth surface its just going to start disintegrating.

You can see here there is no access to the bottom pad at all with the cams in:

If you split the chain then you could pull the tensioner straight up, but they're not designed like that, and tbh thats going to be harder to get right than pulling the cams.

The torque spec for the cam cap bolts is 5Nm + 90° which implies torque-to-yield bolts. They are about £40 a set from TPS iirc (52 in total). I'll get a few in and measure new vs used to see if they actually do stretch. In the meantime, I'll defer to MRC since they have far more experience of with these engines than I do.

notorious · #33 27th December 2016, 02:51 PM

It looks like I'll ned to replace tensioners and chains next time I do cambelt service.

Is MRC the best place to do it? I think Goran recommended 'Unit 20' as well.

27litres · #34 27th December 2016, 07:28 PM

What I wanted to know is if it's feasible to pull the tensioner out through slack in the chains (after assessing with s/t 3366) without removing at least one cam?

MikkiJayne · #35 28th December 2016, 02:06 PM

Unfortunately not - there isn't enough slack in the chain. It needs to come up at least 27mm before it can be swung out.

Goran · #36 28th December 2016, 05:56 PM

Quote:

Originally Posted by notorious

It looks like I'll ned to replace tensioners and chains next time I do cambelt service.

Is MRC the best place to do it? I think Goran recommended 'Unit 20' as well.

Hi Sergei, in my opinion both MRC or Unit20 would be a top choice, they are both well regarded in the Audi community.

Mikki, thanks very much for looking into it, shame its not possible. I knew it would be the bottom pad that's tricky. I was thinking it could be poked off with a chopstick then fished out, but with the cam sprocket and chain in the way I can see it would be pretty much impossible.

Yup its a rubbish design. the whole plastic pad should be sitting in an aluminium cradle so that it cant snap under the force of the chain tension. That way even if it cracked it would be contained in the cradle and continue to provide a soft surface for the chain to slide over. If I had access to a CNC machine it would be interesting to have a go at making a pad shaped cradle to bolt onto the tensioner then cut the pads to drop into the cradle held in either by wedge shape or simply by chain tension.
Admittedly the pad on its own does have some flex and this would be lost if it was in a cradle, but is that small amount of pad flex critical to the chain? my guess would be not.

MikkiJayne · #37 6th March 2017, 08:34 AM

We did this job on Neil's D3 at the weekend, along with the timing belt. It definitely preferably to do it with the exhaust cams left in, as long as you remove the exhaust cam cap at the chain end as well as all the intake caps (both of them in the pic above). This extra one allows the chain tensioner to rotate far enough to pop the intake cam out of the chain, then you can remove the tensioner.

Doing it this way means it can be done without disturbing the timing belt, which is a bonus. The passenger side tensioner is very tight on the belt backing plate, so we removed that to help since most of it was in bits already but I think it could still be done with it still in place. Also, doing one cam at a time means there is little chance of getting it wrong since the exhaust cam remaining in place and stationary gives you an absolute reference of where the intake cam should be. If the notches don't line up afterwards then its simple to see without rotating anything.

Loosening the cam caps was a challenge in some cases as the bolts were stuck, so make sure you have a sturdy T30 Torx bit (preferably several!), and clean any gunk out of the bolt heads first. We replaced all the bolts we removed, in accordance with Elsawin. 40 in total, with 3 cam caps / 6 bolts on each side remaining in place on the exhaust cam. There is no visible difference in the length of the old vs new bolts, so even though they are torqued by degrees they don't appear to have stretched. The new bolts are £1 each, and worth every penny for the peace of mind of having nice clean threads and heads to put back in, and we gave them a very light spray of WD40 to stop any galling going back in so they all torqued up perfectly.

The biggest challenge once we worked out how to get the cams out was actually getting access to the bolts at the firewall end - both for the cam covers and the passenger side rear cam cap which does both cams. There was some fairly tortuous wiggling of tools and contorted limbs to get to those!

5 hours from MRC sounds about right. We ended up at 7 elapsed, with 2-3 people working on it, thwarted slightly by the D3 engine bay managing to be even tighter than the D2, plus Neil's car has LPG so there was some extra pipework to deal with. Its not a 2-person job all the way through, but it definitely helps to have a spare pair of hands to hold the cam while it's lined up with the chain.