eastcoastaudi

I just picked up my 3rd audi 90. I only have about 10k miles under my belt and no real maintenance since my last car was a peach before I sold it..

My oil light came on in my new car within 20 minutes of first driving it. It only comes on when warmed up and my oil pressure gauge reads 1-1.5 bar while warm, 2 bar when cold at idle. Sometimes if I accelerate and then let off the gas the Oil pressure drops and the oil light comes on. There is no lifter ticks and there are a few good oil leaks.

CRAZY_RUSSIAN

first, check oil level
second, change oil to 10w30
3rd check ur sensors,
plug in a mechanical oil sensor.
when cold your oil gauge should be at full

eastcoastaudi

Oil level is right on. Oil is 10 30. Havent replaced the sensors yet but the pressure switch and the pressure gauge seem to be saying the same story. Is the OEM gauge an electrical pressure gauge? I thought it was mechanical. Ill have to investigate further this afternoon.

CRAZY_RUSSIAN

its electrical. when was the last time u did an oil change? if its bean a while, do it, but run some seafoam thrum the motor before changing

turbo510

I've got a '96 A4, with 213,000 miles, and believe it or not, NO drips and very reasonable oil use between 5K changes. With all that I read in the 12V forum about various leaks, I have to wonder if Audi made some changes in later production. Also, I always run 5W-30 and never had a pressure concern. About six years ago, the pressure switch failed, turning on the oil light and also causing a puddle under the oil cooler. Cheap part but very hard to reach!

Lago Blue

This tabbed o-ring (from behind the heat exchanger, on the right in photo), is a famous failure point that will zero your oil pressure fairly quickly as it will blow out side-ways when it finally goes and dumps your sump's contents. It's an age related thing. It's also close by to your sensors that others have mentioned above.

maineman

may be on it's way out also.Only way to be sure is to connect an oil pressure gauge where your oil pressure switch is.

GuyllFyre

I'm having all sorts of trouble diagnosing the oil pressure and leaking problem with my 1993 90cs Quattro 12v AAH V6.

I've got a thread going in the model discussion:

https://www.audiworld.com/forums/sho....php?t=2811242

As you can see, I'm working on it but if anyone else has any suggestions, I'd like to hear them.

eastcoastaudi

So I went and changed the oil. I didnt have access to a manual gauge. The car is leaking a fair amount of oil at the top rear of the block near the valley pan.

My oil pressure is about 2.5 bars upon start up and as soon as the car warms up it is at around 2 bars while driving and then at idle it drops to .5-1 bar turning on my oil light.

I just got the car into a garage where I can dig further but the cars constant oil pressure drop upon warming up HAS to point to some culprit. If I cant sort it out or be pointed in the right direction, Im going to have to dismantle the engine to take a look at it. I guess Im wondering if a leak will cause an oil pressure drop to be that bad? Could a valley pan leak cause the oil pressure to drop?

Lago Blue

Good question and in a word (IMHO); no. Here are seven reasons why:

a.) Often misunderstood, an oil leak from the steadying-chamber cover ("valley-pan") needs to be thought of as more similar to a leak from the oil pan, underneath the engine (see 1st photo), and distinct from a leak anywhere on the pressure side of the oil pump, as the steadying-chamber is simply not a part of that system.

b.) A leak from the valley pan represents a leak from the crankcase vent (CCV) system which is a <i>vapour</i> system. The key to this space's function is indeed in its' name, which defines a (or what should be a) sealed space where oil and air are supposed to separate, the oil returning to the crankcase proper below as a liquid. (see steadying-chamber photo at link):

http://pictureposter.audiworld.com/3...5image0020.jpg

c.) In later models of this engine's configuration (30v's), the chamber cover incorporates a CCV vent hose quick disconnect receiver fitting identical to those found on the rear of each of our valve covers (see 2nd photo below).

d.) True, there are oil supply passages that pass adjacent the steadying-chamber, whose anti drain-back (ADB) valves could theoretically be a source of an oil pressure leak; and would leak into the chamber, but this is unlikely unless they have been removed; and then <i>not</i> re-installed correctly. See Audi TSB here:

http://i2.photobucket.com/albums/y14...heckValves.png

e.) The chamber, which is simply a baffled air hole in the top of the crankcase that the the "valley pan" covers, as part of the CCV system, <i>cannot</i> be pressurized by oil, but is pressurized by air (blow-by past the piston-rings). That oil can leak from under the V-pan is indicative of entrained oil mist, in the crankcase air being blown out due to seal failure under the pan; and perhaps increasing restriction in the CCV system upstairs (further downstream) in the engine.

In particular this increasing restriction can develop in the oil separation screens in the cam-covers (see 3rd photo below). The scum you typically see in cam-covers collects even more readily in the hundreds of passage-ways in the vent screens hidden behind those riveted in place screen retainers. As the passage-ways close off, vapour speed through the CCV system increases, and therefore ever increasing amounts of entrained oil droplets are lost to the engine air intake, and which also foul the EGR passage-way, rather than being halted and returned to the sump; from the CCV system.

see also:

https://www.audiworld.com/forums/sho...5#post24042285

f.) Even if these ADB valves where malfunctioning internally, they would <i>not</i> leak into the chamber, they would simply and only allow oil to drain back; into the sump (see last photo below).

g.) See also discussion (and seventh reason) here:

https://www.audiworld.com/forums/sho....php?t=2811242