Where is the oil leaking from? Advice please!
 

Hi,

My S8 has been leaking oil since before I got it. I didn't think much of it since all of my C4 cars, especially the 2.8l, but also the 2.6l to a lesser degree, give it up like the Exxon Valdez.

After a bit of reading on here though, it seems to me that the V8 engines should be a lot less leaky. Is that so?

I guess I probably would not have noticed the leak so soon if it were not for the conveniently located hole in the noise insulation / under tray. BTW, what is the purpose of that hole?. The oil drips out there when the car is going, and also for a short while after the engine is turned off.
http://forum.a8parts.co.uk/attachmen...1&d=1577429623

Here is a video of the oil leaking when the engine is going:
Attachment 22630

Here is a video of the same area a while after the engine has stopped:
Attachment 22631

Can I ask your opinions as to the most likely source of this oil? The valve cover gasket area seems fairly free of oil and is not wet at all.

Thanks very much for watching!

That's the oil filter cover. If its dripping from that, rather than above it, chances are either the o-ring sealing it to the housing is either perished or pinched. Probably someone fitted an aftermarket filter which didn't come with a new o-ring so just re-used the old one. The Mahle filter comes with fittings, as do some other premium brands, but cheap ones tend not to. The number is 077198563. Unlikely you can get that from Audi any more so the Mahle is probably the best alternative.

You're right that that V8 leaks less than the V6, and the 32V V8 is the least leaky of all' The V6 leaks because its breather system is terrible so tends to make a lot of crank case pressure, pushing the oil out of every seal. The 40V V8 has a good breather system but terrible cam cover gasket design so once that fails it also leaks badly. The 32V has the good breather system and much better cam cover gaskets so is the best of the bunch in that regard.

Thank you once again for your time and willingness to share your knowledge. I really do appreciate it. I suppose that it would be useful at this point to inspect the area again with a telescopic inspection mirror to see if I can determine where that oil that is on the oil filter housing emanates from. Hopefully, a pinched o-ring is all that I have to worry about.

Is 10w-40 semi synthetic a good choice were I to service the filter?

Thank you,

Paul

Yeah clean with brake or carb cleaner and then have a look with it running to see if you can see the origin. The seam between the housing and the cap is about 30mm up from the bottom - just follow the curve. Worth checking the cap is actually tight too - thats the 13mm M8 bolt in the middle of it. Should be about 20nm.

10w40 is fine for the 32V V8 +++

OK....I have decided, after doing as you have suggested, that the oil is perhaps coming from the oil pressure switch that screws(?) into the oil filter housing.

I used a telescopic inspection mirror and could see that there was oil running along the length of the switch. Can i obtain better visibility of this through removing the air filter box/housing, as I have seen reference to on the internet?

Would removing the housing afford me the easiest way to replace the switch if necessary? Does anyone have any suggestions on how I may best proceed?

Thanks as always,

Paul

Yes removing the air filter box is pretty straightforward, and will afford better access to the oil pressure switch. From memory the 32V has the early type with the single spade connector - those were prone to leaking so not surprising its coming from there. I don't recall the exact layout of the 32V tbh so can't comment much on what contortions or special tools you need to get the switch out. Its non-trivial on the 40V!

So, I finally got around to taking the airbox out. Seems like the oil leak is at the pressure switch as I assumed.

What would be the best tool to get the switch out? I gather that there is no point in trying to tighten it.

I have read that you can't get a deep socket in there(i would have to buy one to find out). Advice is to cut some of the switch off so that a normal 24mm socket will fit.
https://forums.quattroworld.com/a8/msgs/39651.phtml

Any better suggestions? I could try vise grips. Not sure how much torque is required to fasten it though.
Attachment 23132

It's not a fun job, but better on the 32V as the terminal is much shorter. You may find a standard 24mm socket will fit over that switch. If not, a long socket could be cut down so it fits between the switch and the chassis leg, and then grind some flats on to the body of the socket so you can get a spanner on it.

It doesn't need a lot of torque to reattach as it has a crush washer. If you can get enough torque on it to get it out, you can easily get enough to put it back in.

Thanks for the hints. I tried a normal socket for fit but the terminal almost pokes out the back end, meaning that I would at least have to cut the terminal off or bend it over.

I think I may have seen long sockets with flats before. Maybe I can look for one of those. I have a breaker bar with a small profile so maybe things aren't as difficult as I am imagining.

It looks like the oil could be leaking from the plastic part of the switch near where the terminal is. Is that a thing?

Yep thats the normal failure mode for them +++

Standard long socket + angle grinder = long socket with flats ;)