gOOOOran

good point, I would not want brass shavings in my engine either.

spitanddirt, most of the ebay pads seem to be sourced from China. Considering the plastic has to be a very specific heat and oil resistant material, I would not want to put the ebay pads in my engine. I bought 2 only to test and use for dimensions. There is a post on the A6 forum which I cant find right now, where a guy had his old OEM pad shatter, then replaced it with one of the ebay pads and that broke too very quickly. Of course it could have broken due to some other problem, but I am suspicious of the ebay pad material. I would only trust OEM pads (which Audi doesnt sell separately) or pads machined from a known improved material such as Stanyl Nylon 46, or Stanyl Diablo, or Duratron CU60.

Here are cad drawings hopefully detailed enough for machining chain tensioner pads from a 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.

spitanddirt

So a question for silverd2: how many miles have you put on your A8 since replacing the tensioner pads? What is your take on the Ebay sourced(China) pads? Are they at least OEM quality? Comments? I mean, right now, it seems that's the only option short of sourcing the entire tensioner. What's the track record from someone who's actually currently using them?

silverd2

Not that I'm recommending it, but I bought these because they were the cheapest...but am not worried about early failure either.

http://www.ebay.com/itm/00-03-04-Aud...=mtr#vi-ilComp

The material seems to be the same as the internal part (original, before "aging"...see post #5 this thread)and the old one made it past 100K.
Plus I'll be changing the tensioner eventually anyway...lots of start-up noise and occasional codes on that side...bank 1 adjuster malfunction & over-retarded.
The pad replacement was a life-extending measure and a learning experience.

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

When I find a deal on a tensioner, I'll jump on it...not in a hurry to pay the $550 going rate, though...esp when I have no worries about damage due to failing tensioner...it has a heavy spring in the piston that keep a bit of tension on the chain, enough to prevent timing jump.

The worst thing you could do, is to run the car (at all) with a pad missing completely...even with a perfectly functioning tensioner...guaranteed to shred the piston in no time and jump time.

So, for now, I'm puuting up with the start-up noise...can't feel anything but "smooth" on acceleration...the tensioner is still doing it's job most of the time...just occasionally not advancing that side fully...can't feel it though.

gOOOOran

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 blasted Audi sold the pads separately I would be quite happy to put 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.

gOOOOran

Few more pics, not sure if they are useful.

silverd2

Glad you're keepin this discussion going...but in my case, not because of pad material choice, but the actual operation of the adjuster...And I'm realizing more ane more as this goes...and rethinking a few things.

First, my upper piston pulled right out, too...looked just like the A6 version you have. According to Audi, if that tensioner is off a 4.2 40V A6 engine, it's the same design (locking pins included). But, looking at the drawings below (out of Audi's mechanic home study program) the pins lock the "adjusting piston" (the bottom one) in retard position (slightly extended) which mine definitely was while out AND on first inspection before removing, yet I had slight slack in the upper chain already**. The upper piston is the tensioning piston and not locked.

Even though these drawings are from Audi, I have a few problems with them...apparent discrepancies...parts missing or misplaced in drawings(?)

The drawings show no spring in the upper piston (just an oil reservoir), but DO show one in the lower (adjusting) piston. Plus, the first drawings show the locking pin mounted high (at upper piston..incorrect)...but the second drawing shows the locking pinS mounted down low (at adjusting piston) where they (it?) should be...but again both drawings seem to show an internal spring in the wrong place and/or one missing where we both know one exists, in the top piston!!!!

This is making me rethink (VERY early in the process, though..more to come) the whole reason for start-up noise and the real purpose of the locking pin(s).
A basic rule of starting any engine is that the ignition AND (if present) VVT MUST be in the most retarded position...SO, some means of keeping the VVT locked in retarded position till oil pressure and ECM commands take over would HAVE to be in place anyway...noise or no noise. Otherwise the ECM would have to trigger some other added-on means (solenoid or similar) of retarding the adjusting piston...therefore, a mechanical means: the locking pin method.

** As I stated, although a steady start-up noise maker (then and now), my adjusting piston (lower) was correctly (from what I could see) locked in retarded position, yet the upper chain was loose enough to sag a bit...THAT should not be...you could NOT over-tighten this chain with the tensioning piston...it's just a spring against a beefy chain.

So I am beginning to wonder if start-up noise has nothing to do with the locking pins, but possibly the the tensioning spring relaxing with time and heat...but less likely (not impossible though) a slight stretching of the chain...or a combination of both(?)
...Who knows at this point...Audi is not forthcoming with info and even the info supplied to their mechanics (who do NOT repair these units...just replace) is suspect and inconsistent, as the drawings indicate.

A deficiency of non-hydraulic chain tension (weak spring function & fit) could theoretically not only lead to start-up noise, but also (maybe) a failure to fully advance the timing (leading to failure codes). After all, if that part of the drawings is correct, the apparent function of the hydraulic pressure is NOT to tension the chain (vent/pressure release on top piston...it would be sealed piston, which it is not) but ONLY to move both pistons up & down as a unit through the adjuster. According to the drawings, the 2 chain pads (piston ends) do not NOT change their distance relation to each other in ANY phase...engine off, advance or retard positions. So that measurement, therefore amount of chain tension (any phase) seems to be only regulated mechanically (spring tension/chain length)...NOT hydraulically(?)

Since I'm a curious type, have a loud start-up, too cheap to buy a new adjuster if not totally necessary and I have another new valve cover set in the box anyway, when warm weather and a spare day comes up, I fully intend to get back in there again and try something. It's a ways off and I'm still at the drawing board, but I'm thinkin the easiest thing to try with existing equipment, is to shim that upper spring (proper sized washer(s) to net an upper piston extension that results in a very tight chain on re-installation, with the lower (adjusting) piston in it's properly locked (retarded) position.

May not work, but there's something missing in all the info I've gathered from all sources...and have never heard a solution, other than spend the bucks and replace the entire unit. Units are made up of parts and parts fail. If an accessible part is the possibly cause, I'd like to know.

Will update...and would love other opinions, esp if you see flaws in this logic.

silverd2

P.S.
I now notice that your A6 tensioner appears to be from a V6...2.7T(?).

Not sure, but I believe any A6 motor with VVT is a 5v design and includes the adjusting piston locking pin design.

gOOOOran

Your description makes perfect sense to me. That my understanding of the Audi diagram also, that the tension is set by the bottom spring, and that the two pads move up and down, not increasing tension just moving the chain to being straighter at the bottom and more curved at the top.
Using this logic I also dont understand why there would be a start up rattling noise if the tension is already set, all the time, by the bottom spring, and the piston just held in a particular position by the locking pin.
I thought maybe the oil drains off after a long time, but then the same noise would be present in a brand new car sitting for a few days.
I think you may be onto something that the spring gets tired after 10 years and doesnt provide the same tension.

Audi diagram is definitely confusing, I did not expect to find the top spring in the A6 piston, and didnt expect the piston to fall freely out. There are two holes in the piston, but I could not find a locking pin in the variator body. I'll have another look tomorrow.

Like you I really dont want to spend £300+ per side to replace a working unit not showing any errors. If there is a way to repalce or exend those spring, and the pads of course, that would be perfect.

I'm looking forward to your findings when the weather warms up.
I'm now really desperate to open my valve covers and just have a look at the state of my pads, do you think its ok for me to just keep the old gasket in there (if it doesnt fall apart) just to have a look, since I am planning on changing the gasket soon anyway. Is it not too critical if after opening and closing up again those old gaskets leak a bit?

Thanks

gOOOOran

I just looked at the diagrams again, I misunderstood. The locking pin must be in the bottom, thats why it wont move up and down.

gOOOOran

I forgot to post the part number for the A6 variator I have.
058 109 088 E