A8CT

ok - got it, thanks guys. Just ordered one from the link you posted.

Dr. Jitter

Hi Bob!

First, you have to know there are two stages of motor oil "eating"

1. problems with cylinder heads: after 100k miles there are not only
valve steam seals, often it's valve guides! If you change only rubber valve
seals and you have already worn guides it gives a result for 20k miles,
not greater. Of course, I can post you instructions how to change them
if you want. For changing valve guides you have to remove cylinder
heads and you need professional guy to repress them. I combine this
operation with toothhead belt replacement. I removed cylinder heads
and when I disconnect springs, plates etc for valve free movement
i found rather big clearance between valve and guide. Guides reinstall
work was made by my friend only for 400$ (two heads). All repair works took 1 week. I changed all belts, thermostat and camshaft seals.




2. problems with piston rings. Often happens with rubber oil scrapper ring when motor was overheated - a lots of blue/white smoke when drive hard


P.S. If your car has a light puff of smoke when started hot and there is no blue/white smoke whe idling it's a problem with motor heads/seals.
BTW you have rather good plugs. Are you sure it's not a bad seal somwhere? Before "very end" of motor life compression raises because oil tighten worn rings.

MP4.2+6.0

<center><img src="http://pictureposter.audiworld.com/26081/img_2246.jpg"></center><p>
Saw your request to check in on the D3 board...
Picture shows top of motor when I did a stem seal change--referenced way below.

I would want to see the plugs closer up, but preliminarily I'm not convinced there is a stem seal issue here, at least so far. Nor am I convinced there is a water issue so far either.

First thing I would do is nail down if there is a water issue. If you are losing no coolant, measured at the overflow bottle over several engine use cycles when cold, then that is definitive. If the level is slowly dropping, you need to look for any possible leaks. If there are no external leaks at all, that means to me usually a head gasket but low probability chance of an internal engine or head crack. BUT, my experience on modern Audis (i.e. not the ancient C1 which was notorious in the head gasket area) is virtually every time you may think there is no external leak, there usually is. You may not find it easily because it hits and burns off the exhaust, it lands on the belly pan and then blows off when driven, it is a pinhole at the radiator that evaporates off and things like that. Engine removals and teardowns are $$ and no fun, so really work hard to find elusive leaks first. And of course if the heater smells, it's a heater core leak, but I'm guessing you would know that one if it were to happen.

In any case, first diagnose for any water leaks over several motor warm up cool down cycles.

I'm going to guess the residue on your other plugs is just because they are running cooler or hotter. The lower compression you have on one side would also give lower running temps too. I have actually found that if a head gasket is leaking, the plug and cylinder where a water leak occurs look very CLEAN. If you think about it, it is because you are literally steam cleaning them. The usual tip off if you are losing water and it is a head gasket leak is billowing steam in the exhaust, way beyond what you get for a few minutes on a cold morning.

My net around your plug residue suspicions is I would run though some good upper cylinder/valve cleaner type stuff as a starter. Simple and cheap. Maybe a few cycles of Techron and other solvents oriented at valve deposits. I'm thinking maybe you have some build up on the valves and it could be interfering a bit with their operation or even absolutely complete seating. Also look carefully at the thermostat function. Any chance it is stuck open or part open that is having the engine run cool? Have you ever changed it? By your mileage it's a suspect in any case if it has never been serviced.

Another area to look at for oil burning--the "suck pump", which has several other names too. Basically Audi terminology for the PCV valve. On most Audi's, including my C5 it is a black Y shaped part clamped into some lines--they kind of look like oversized hard plastic vacuum lines. If that is jammed or somewhat clogged, more oil can get pulled through it. Search the archives for D2 specific info if you are not familiar with it. Again a relatively cheap fix and standard long term maintenance anyway.

Finally on to the valve seals (and related guides). In addition to your compression test which gets more at piston rings and bent valves, you should first just do the general visual test. The classic test is to find a long downhill descent that you can take at speed--a mountain downhill stretch, or at least a long freeway offramp where you can shift down. I have found you need 10-30 seconds of being able to shift the tranny down in the gears. By doing this, on the intake side of the motor you are really loading up the vacuum level if you are revving the motor by only shifting the tranny down while keeping the throttle closed. If the intake seals or guides are bad, it will pull oil through and you will see it in the rear view mirror as exhaust smoke. When you see this, but not general oil smoke (typically somewhat blue in color) under normal engine operation, it is a strong indicator it is the intake guides or seals, rather than the rings. And by contrast if you see oil smoke in general in constant operation, that suggests rings. The intake seals are the ones more likely to go first due to this high vacuum during deceleration, and are more likely to be related to general oil burning in my experience.

Returning to something you alluded to, yes I have changed valve stem seals on a C5 4.2. You do it by applying air compression through the spark plug hole while using a tool to release the valve stem circclips and then disassembling the valve springs. First you basically need to do a cam belt job, so plan on a timing belt renewal at the same time. The cam/timing belt needs to come off because you need to remove the cams to get at the valve drivetrain. My posted picture shows how far into the top of the head you need to get, though it doesn't show the tool of the air applied at that stage. Having done it, it is an 8-10 hour job. You can buy the tools via Zelenda or someplace similar if you do that.

First though, try the easier stuff like a thorough couple of cycles of Techron and similar valve type cleaners, and running down any water issues that might suggest a head gasket issue if there is no other leak explanation. If you found a head gasket leak of course, no sense doing the time consuming on car valve stem removal.

For reference by the way, I still haven't cured my issue. It is in cylinder 3--I have one and only one oil fouling plug. I still need to check compression too. I suspect when I tried to fix it last time I may not have seated a stem seal--not enough force with the right install tool. On mine, I suspect it is in the exhaust side, since I see smoke at start up and suspect it is running down the exhaust valve when the motor is off. I have changed the belt, but never the water pump or thermostat, so when I go after that as part of a belt change I am going to make one more run at the seals. If it's not that, then my guess is mine is some head crack fluke or maybe a bad oil scraper ring or seriously bad valve guide where the seal can't hold it enough. The compression test will help me i.d. obvious ring issues too.

Good luck.

A8CT

heads that I could have re-worked and ready to go if do it. That would save me some down time.

Any ideas/tips, please post or email at rdunne14@comcast.net

Bob

A8CT

I'll pick off the easy things first:

1) I have replaced the suck valve and the other "valve" that sits on top of the motor towards the back.

2) Thermo was changed by the dealer before I bought the car. No overheating issues at all, it stays right at 11:00 in any conditions (perfect on the A8)

I'm going to put it on the lift, it's due for an oil change anyway and give it a thorough inspection.

At the last change, there were no signs of any coolant or oil leaks, bone dry all around. The funny thing is I don't have a record of the oil cooler being fixed. I keep checking it because it's WAY past the mileage compared to other D2's I've owned to not leak.

I keep checking the coolant too for any oil residue, nothing yet. I would be happy to make this repair if that's where the oil is going.

I'm going to try some agressive valve cleaning solutions in the meantime....

thanks
Bob