cam chain tensioner shoe - can it be improved?
 

Hello,

I know they rarely go wrong, and can last over 300k miles, but I cant help wondering if they could be made from better material?
It would be nice to replace them with better ones when doing the cam cover gaskets at some point in the future.

Would aluminium be a bad choice because it would cause wear on the cam chain? (aluminium being tougher than the nylon plastic used on oem shoe).
Also I guess the chain running over an aluminium shoe would generate a lot of aluminium dust which would end up in the oil.

Is there a better plastic that bends rather than breaks, and that would not become brittle from heat inside the engine? I read about glass reinforced nylon would that be good?

Just out of curiosity I bought one of these from ebay, I'm going to do some destructive testing on it to see if its any good.

http://www.ebay.co.uk/itm/Vw-Audi-ec...37252755803325

I have been searching around and a picture from this website gave me an idea. If someone could make us a aluminium or steel casting with the plastic wear surface locked in like in this picture, it would be unable to brake off at the edge.

http://www.murtfeldt.com/products/ch...el-c-profiles/


some more info (I'm bored :) )

http://www.eng-tips.com/viewthread.c...=292501&page=1

so from the above it appears the Audi geniune ones that are creamy in colour are probably made of Nylon 4.6 (the better stuff) and the darker colour aftermarket ones are probaby the older type of Nylon 6.6 with added graphite as per above forum. However those assumptions are just based on the colour of the different pads.

Another find. Porsche pads appear to be almost the same as our pads. Except ring on bottom one and no holes. I'm hoipng to get a couple to see if they are are the same dimension wise, a hole is easy to drill if needed.

Porsche pads are different, they dont fit Audi variator!
//Maybe another option for replacement with a genuie OEM part since Audi wont sell us their pads individually.
//UK:http://type911shop.co.uk/shop/articl...6aid%3D2887%26
//States:http://www.koperformance.com/part-nu...ENUINE-PORSCHE
//Porsche part no. is 99610525300
Porsche pads are different, they dont fit Audi variator!

Does anyone know what the hole is for on our pads? is there a oil squirter or someting in the variator body that squirts oil through that hole or something?



Message for Nollywood: please ask your engineering friend who may make pads for us to look into Stanyl Diablo (recently selected by Fiat) and Duratron CU60 (apparently one of the toughest high-temperature plastics).

http://www.quadrantplastics.com/eu-e...ron-R-pbi.html

http://www.dsm.com/en_US/html/dep/ne...nyl_diablo.htm

more info. Stanyl are still pushing PA46 as the way to go for chain tensioners. Looks like they are the suppliers to the factory that casts the chain tensioner pads (still havent found out who that is, could it be Borg-Warner?). Although I could be worng, other factories make a material called PA46 too but with different properties, for example:

http://www.piedmontplastics.com/prod...n-46-pa46.aspx
300F is only 148C, not much above engine operating temperature.


http://www.dsm.com/en_US/automotive/...ng_systems.jsp
"The material gives you solid performance across the engine’s lifetime when dealing with high chain tension"

I have to disagree with them, the pad failures that have been posted so far is proof to me that PA46 starts losing its structural properties after approx 100,000miles in a engine oil environment, which is hardly the lifetime of the engine. Unless our pads are made of some other weaker PA46?

I posted on the Porsche forum, they say that Porsche updated the material for their pads.

http://986forum.com/forums/performan...-cleaning.html

*edit* - I received the Porsche pads, they look very nice but shape is different they wont fit Audi variator

The best way to improve would be if the tensioners have three rollers (sprockets) for the chains to ride on. Less friction, though would be quite expensive to engineer as aftermarket items.

rollers or sprockets are an excellent idea. Unfortunately the cheapest design option, replacing the pad with rollers without re-designing the variator body, is a bit space limited. The pads are only 7.5mm high above (and below) the variator body plate, leaving room only for small rollers (so really 5 needed ideally), with worryingly thin material thickness available. For example, roller drum (plastic) 2mm thick. Roller shaft (steel) 3mm thick. Roller bracket/frame (steel), thinnest point 1mm.
Here is a quick snapshot of the drawing I was preparing for the machining of pads out of a better material.

! Also, I received the Porsche pads unfortunately they are the wrong dimension, dont buy !

interesting post on the A4 forum. McGyver fix :)

http://forums.audiworld.com/showthre...=349969&page=3

Here are cad drawings hopefully detailed enough for machining chain tensioner pads from better material. One is the 'original' pad, dimensions taken from a Chinese copy pad bought from ebay. The other is a simplified version.
Use at your own risk, I take no responsibility if dimensions turn out to be wrong, always verify dimensions from Audi original pads or the mounting plate on the cam variator.

Me again :)
I wanted to check dimensions of the variator, so I got a cheap used A6 variotor from Ebay. Also allows me to practice putting on the macined pads (if I ever manage to convince someone to make them for me from that tough material).
The pads on this variator (mileage unknown) seem to be in pretty good shape, not too worn. I took one off a couple of times and it didnt brake.
If only Audi sold the pads separately I would be quite happy to stick in a set of new original Audi pads and change them again in another 100k miles.

Dimensions of pad mounting plate are 51mm x 14mm x 5mm, so the drawings I posted before seem to have the right dimesions for the mounting section.

The piston of this variator just comes out by itself, doesnt seem to have the locking pin that our variators are supposed to have that only release with sufficient oil pressure.

It's a shame VAG don't recognize the common problems with there cars and sell just parts you need, at a reasonable price, as far as tell BMW Mercedes and Porsche seem to sell me what ever I need. This keeps the cars economical to repair, which keeps them on the road, and seems to help residual value, Which helps sales. I couldn't recommend any modern VAG product to anyone, and I don't. The breakers yards a littered with cars that could be repaired, Or engine & transmission problems that just shouldn't happen anymore. Soon we will all be driving KIA,s
Dave

Pad obsession continues with new car.
I caved in and ordered these pads. There is no way I was going to give Audi another £950 for 2 chain tensioner units when my old ones appear to be working just fine.

http://www.cs-parts.de/index.php?a=237

They are going into my car shortly, I plan to open up cam covers in around 1 years time to check how they are doing.

If anyone else is contemplating changing their pads, and is determined to have original Audi pads, there is a middle way. Ask your Audi dealer for part no. 058109217B or 058109217D, the price of each unit is £140 + Vat, if they can do you a discount it may be possible for around £300 for the pair. You could then try to sell the units on ebay to anyone who wants a discounted genuine unit but is happy to risk aftermarket pads.

Picture of cs-parts.de pads

http://forum.a8parts.co.uk/attachmen...1&d=1394653682

Goran, I'm following this thread with interest. When I first open cam covers I will look at pads of course and will be changing preventively.

Sergey, please take pictures of your old pads. I have my old pads from the previous S8, I will post pictures of them. Taken out at around 112k miles in 2012.

This is def a interesting thread. My car has 149k Miles on it and if these wear out and cause engine failure they need to be checked

So you bought yours from cs-parts? and 2 sets are needed(4 pcs?)

Just did the fuel pump change so might just as well go ahead and do this also;)

:)

In the link above it was 5 euros per pad, you need to order 4, so 20euros total. If you plan to do it yourself best to order the combo with special tool 3366 and gaskets.

Its a worrying issue. Some cars have made it beyond 200k miles with no apparent problems.
It doesn't seem to be an epidemic, with A8's at least (lots more failures on web with A4's)
I'm not sure what the primary cause is, heat? oil? heat and oil? mileage or simply length of time in engine, ie, degradation with age.

Its definitely worthwhile at least opening the cam covers, to change old gaskets anyway, and check the tensioners, if they look very worn or close to cracking definitely change them.

Here is Sam's guide on quattroworld when he took out his. MRC will be taking out mine using this intake-cam-only method to save on labour.

http://forums.quattroworld.com/a8/msgs/55496.phtml

I have thought about this a lot. I am really curious if there is a fiddly, but possible way to change them out without taking out the cams at all.
At this stage it is purely theory as I have not had access to a open cam assembly to test it out. I will try to describe what I was hoping to try.
Once you have the cam covers off (following Audi procedure up to this point):

1) depress edge of tensioner pad mounting platform enough to be able to slip the top pad off without special tool 3366

2) slip a piece of card between metal pad mounting platform (on top of tensioner piston) so that chain is not resting on metal.

3) using special tool 3366 depress the tensioner piston. This should allow extra slack in chain compared to Audi procedure which requires tool 3366 to press down on the old plastic pad still in place.

4) rotate intake cam to move chain slack to the bottom of the chain. Secure with rubber band or something. Chain tensioner still installed.

5) using a length of sticky tape (electrical tape), get the tape to slide between the chain and bottom pad. This part is theoretical there may not be enough space to do this.

6) with tape stuck on the bottom pad, use a thin plastic or wooden rod (you dont want to scrape metal to metal in there) to pry off the bottom pad. I have tried this with a removed tensioner it is easy. It will work with a installed tensioner only if there is enough room for the plastic rod to reach it.

7) carefully pull out bottom pad using the sticky tape stuck to it.

8) unbolt tensioner unit and lift just enough to scrape off old tensioner gasket and install new one. bolt chain tensioner back in place

9) cut a long lenght of electircal tape and stick it onto the face of one of the new pads.

10) carefully manouver new pad using the tape down to the bottom of the chain tensioner. This may not be possible. Even if it is possible it is likely to be very fiddly, and may not save any time compared to unbolting and removing the intake cam. This was a method designed for someone not competent to mess with a cam (ie, me).
I wanted to try this because I was more scared of unbolting the intake cam and getting the torques or timing wrong when bolting it back in.

11) with pad in place pull with tape until it clicks securely into position. remove tape.

12) remove tool 3366. Press piston by hand so you can fit a new pad on top of tensioner. Job done.

Even if this method doesn't work, its a free try, in other words you just carry on with the proven procedure of removing the intake cam.
If you are confident taking cams out, and getting the torques of cam caps and timing right, this is a pointless procedure.

I have attached the original ElsaWin procedure for both right and left tensioner/adjuster unit. This is for a 2001 S8 AVP engine. If anyone wants procedures for other engines please ask I will upload them.

If your engine is Pre-Facelift, relax, you are safe :)

I have had my pads changed at MRC. Surprisingly it only took them 4 hours, for both banks, I was expecting it to take longer considering the complexity.
So total cost was 4 x £68 x 1.2 = £326 plus 20 euro for 4 pads.

Here are some pictures, these pads taken out at 120k look a little better than from my other S8, those were pitted at the top too and one had a large crack developing.

I am a engine hypochondriac, so for me this preventative maintenance was worth it for the peace of mind.

I would still like to try removing the pads without unbolting cams. If someone has a old or damaged head, either side, I dont mind driving over to try this procedure. I have 2 old tensioner units and the tensioner tool.

http://forum.a8parts.co.uk/attachmen...1&d=1398101929

http://forum.a8parts.co.uk/attachmen...1&d=1398101995

http://forum.a8parts.co.uk/attachmen...1&d=1398101995

http://forum.a8parts.co.uk/attachmen...1&d=1398101995

http://forum.a8parts.co.uk/attachmen...1&d=1398101995

http://forum.a8parts.co.uk/attachmen...1&d=1398101995

http://forum.a8parts.co.uk/attachmen...1&d=1398101995

http://forum.a8parts.co.uk/attachmen...1&d=1398101995

http://forum.a8parts.co.uk/attachmen...1&d=1398101995

http://forum.a8parts.co.uk/attachmen...1&d=1398101995

http://forum.a8parts.co.uk/attachmen...1&d=1398101995

http://forum.a8parts.co.uk/attachmen...1&d=1398101995

I bought 4 pads and the compression tool from cs-parts.de, but never got to fit them. I someone feels brave enough to try - £15 posted :rolleyes:
http://www.cs-parts.de/index.php?a=709
says they fit 2,4 30V / 2,7T 30V / 2,8 30V / 3,7 40V / 4,2 40V

Just as an update, my engine hasn't blown up yet with those pads from cs-parts.
I hope I haven't just jinxed myself :)

So MRC didn't change the chains or the cam cap bolts then? Etka says to replace the bolts, but 52 of them is a fair overhead.

I like the idea of changing the pads in place. I might give that a shot on my spare head just out of interest. Leaving the exhaust cam in place is a bonus time-wise and also for oil seals etc.

+++

I have a complete spare head (with bent valves) if anyone needs a test mule. It has the existing tensioner with worn (160k miles) pads on it.

No I am pretty sure they didn't change the cam cap bolts. I hope that's going to be ok.

I am sure the pads can be changed in place. The bottom pad is the tricky one of course. Once the top pad is off, there should be enough chain slack to do the bottom pad, its just a matter of devising some make shift tools or a bit of strong sticky tape to allow the bottom pad to be manouvered into place then pulled so it snaps on. If you do go for it please please do a video or some pics of the method that works.
I really wanted to try it myself but the 8 went in for other work so I asked them to do it with the cam wiggle method. I don't think they could be bothered to try the pad only method. Probably too frustrating.

Where abouts are you? I wouldn't mind having a practice on it. If its something that can potentially prevent a more serious failure and there is a cheap easy way to do-it-yourself its worth finding out.

Which side? I need a passenger side which can be rebuilt. My proper ****ed passenger side head can be used for testing this theory :) (although I have a couple of each)

Passenger side. I'll take a couple of pics over the weekend
Only reason why I didn't rebuild it was that the car came with a 'good' head courtesy of the forum sponsors already in the boot

I'm in Belfast but will be over in England in the new year and can chuck it in the boot

+++

Goran - I'll try this between xmas and NY and post up what happens :)

Thanks Michaela +++
I hope you have success with it.

I'm well jealous really want to have a try too :)

Where are you based? You're welcome to come down to Devon and we can give it a go together :)

That's a great offer, thanks! I'd be there like a shot if it wasn't for the distance, i'm in east Kent, wrong side of London :)
Let me know which day you are going to give it a go, I might come if I get fed up of all this time indoors.

+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...

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 :(

http://www.corradov8.com/pics/s8/tensioner1.jpg

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 :mad: 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:

http://www.corradov8.com/pics/s8/tensioner2.jpg

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.

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.

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?

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

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.

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.

:cheers: