Madhavok

Long time reader, first time poster!
1995 Audi 90 quattro sport 2.8 v6 117K on her
Noticed quite a bit of oil leaking this morning after driving to work. Did some digging around and (hopefully) most signs pointed to the oil cooler o-ring.

Got the ring, removed oil filter, nut and the threaded tube hoping I could pull away the cooler enough to get to the o-ring. Not happening. It almost seems the cooler is attached to the oil pan. I've read to maybe use a flat head to easily pry at it. Basically I'm trying to avoid taking off the hoses if at all possible.

Am I missing something?

Thanks!

Madhavok

I got it off. It was on pretty snug. Anyway, the o-ring in there was fine and intact. It was flat compared to the circular new one I have. I didn't put the new on on, just thought it wasn't on snug. Anyway, put it all back together, still leaking. But it's not leaking where the flange meets the cooler, but above that. Possibly the gasket between lower and upper pan?

I'm going to put the new o-ring in and try again, but I feel it's not the o-ring of the cooler.

Previous owner put a new oil pan in before I bought the car. Could have have maybe over tightened the pan screws?

Rusty Spokes

Those oil cooler "O" rings do get hard/brittle and start leaking from time to time. When it gets cold outside they can blow-out and cause some concern. The oil pressure switches behind the cooler are known offenders for oil leaks too.

I do replace my oil cooler "O" rings when I buy a used Audi 2.8 12v. Part of the preventive maintenance. If fact, I have replaced the oil coolers too.

I have not discovered a way to change the "O" ring without either removing the threaded center tube or removing the coolant hoses.

Removing the center oil filter threaded tube is fiddly. I have a pair of threaded nuts that I thread/lock/clamp on to lower part of the tube. That usually works.

I found it just easier to remove the oil cooler. I may replace it and I will replace those hard to get to coolant hoses too.

The oil cooler fits in one particular location, if you remove it. There are some tabs on the flange behind the oil cooler that must be positioned so as to not damage the cooler when you tighten it back up.

If you do remove the oil cooler..look back there behind it and you will see some oil pressure switches (could be one..or two)..they are notorious for leaking oil and creating a mess.

That is part of my routine with a used Audi. I do change the oil cooler "O" ring, the coolant hoses (in particular the hard to get to hoses), the oil cooler (surprising inexpensive from FCP Euro for a Behr oil cooler..about $50), oil pressure switches (only use OEM switches from VW/Audi), oil change and change/flush out the antifreeze. If the antifreeze has been neglected and there is a lot of rust in the system, I change the radiator and drop the small threaded "block drain" under the back of the engine and run a lot of water through the block till all the rusty debris is gone.. Use a new "O" ring on the "block drain" if you do remove it.

Madhavok

Put the new o ring on and while it was idling, no oil was leaking. Took it for a drive and started to leak again. I looked up and I think it could be coming from the oil pressure (white looking area) switch. It looks to be oily and fresh above the pan.

The previous owner kept this thing in great condition. Bay of the engine looks brand new.

How how involved is the change of oil pressure switch?

I was able to swap o-rings by taking off the filter, nut, and threaded tube, pried away the cooler with the hoses still intact.

Rusty Spokes

Don't know if you have the AFC 2.8. These pictures show you where that switch lives. Might be two oil pressure switches. If so they work differently, one being a high speed switch that grounds to earth at about 1.8BAR part number 056919081 (could be a white color)..the other has an open circuit to ground once the oil pressure gets to .25BAR part number 028919081H (could be blue switch..or dark color)

A 24mm deep socket and a 24mm open end wrench may help get to the switch once the wire is off..or an oil pressure switch socket tool from a local auto parts store.

I recall it is fiddly to get to the switch(s)..sorry to say it helps when the oil cooler is off. It is doable with the cooler on with some contortions. Don't strip anything when you snug the new switch in. SNUG tight is good enough.

Madhavok

Thanks Rusty.
I looked at the info in the spare tire area and it said engine family AFC.

I have a friend who when I get the switch can get it up on the lift at our work to get it figured it out.

So of its switch right behind the cooler, it should be the white one, correct?

Maybe I'll just buy both and return the one I didn't need.

Madhavok

Wasn't sure how to edit my post. I've included a picture of the leak.



No audi dealers nearby, but local autoparts store has the switch - the one which is right on the filter housing area as described by you, Rusty.

Rusty Spokes

A lift will help for sure. Get both switches and if you have two back in there..replace them both. Yes..the white OP switch..there may be a rubber boot over it..when you pull the boot off the switch..see is there is a puddle of oil inside...if so..its leaking.
Take some pictures too for others in the future.

Rusty Spokes

Super..and that switch is definitely leaking. If you have a VW dealer..or for that matter a NAPA store..get the switch(s) from there. The VW part number is the same.

If there is a NAPA store..get the "Altrom" oil pressure switch. Altrom buys them in Germany from the OEM supplier and sells to NAPA. They are good switches. Some of the aftermarket switches are of very, very poor quality. NAPA part number ATM 056919081E for the 1.8BAR white switch.

NAPA part number ATM 028919081D if you get the blue .3BAR switch.

Madhavok

Thanks, Rusty. You've been a great help.
The NAPA rep I talked to didn't have that exact part - had the 2.5 bar version and would be here in a few days. I can order the exact part you gave me for the white switch via napa online and have it delivered to my house - 1.8 bar.

Carquest can have it tomorrow, but also the 2.5 bar (red).

I do have the VDO gauges in my car if that makes a difference.

NAPA rep said didn't really matter between the 1.8 or 2.5, but that's where the pressure would be gauged.

Anything below 1.8 (I read) was too low of pressure. So if I put the 2.5 switch in, then anything below 2.5 on the gauge would be low?

Thanks again.