oil press warning

[Phil Rose]

At 10:45 AM -0400 9/4/04, feelstranger wrote:
>Hello all,
>I have a question, but first the story...
>Last week the SO was driving the 200 on a hot day along the Mass 
>pike and had the oil pressure warning light beep at her several 
>times.  She pulled over several times and checked the oil etc (smart 
>girl).  It was fine (I know the light is not for the level - she may 
>not have).  She kept going and she said that when she shut the AC 
>off it never did that again.  She made it to Saratoga (in none to 
>great mood) when she picked me up and we drove back to VT with no 
>warnings and the oil pressure stayed in the 5 range while motoring. 
>It has acted normal up till yesterday.
>So I get in the car and start it up (first time for the day I think) 
>and the oil warning goes off.  I look and see that the pressure 
>appears pinned at the 5 position at idle.  I seem to recall that the 
>pressure sits a little high just after cold starts - but maybe 
>not....?
>

Cold pressure briefly at 5 bar is OK , but the gauge should return to 
a lower reading (about 2 bar?) when idling a _warm_ engine.

>So the question is...  Will over pressure tip off the warning?

There are two pressure sensors--low and high. So, yes, it can react 
to excessive pressure. But although I've often seen 5 bar briefly 
during warm-up, I've never had the pressure warning. The ECU 
considers the combination of RPM and pressure (and perhaps engine 
temp) to decide on whether to issue a hi/lo warning. The "critical" 
RPM is about 3K, I believe. I'm sure some lister knows the exact 
parameters for oil pressure warnings.

>Are there any known electrical issues with this system?

This is an Audi, right?

>I really get the feeling this is a gremlin but maybe that is just 
>wishful thinking.
>I'm running 20w 50 dino oil.

The 20W 50 weight could be an issue I suppose--why such a high 
viscosity range? I'd guess a defective pressure sensor (not uncommon) 
is the more likely culprit--something I've escaped so far (knock on 
zebrano).

Phil
-- 

Phil Rose
Rochester, NY
mailto:pjrose at frontiernet.net