Hi Guys - I have been super busy and do not have a lot of time to fix this issue, but my mom's '01 A6Q 2.7T started throwing the red oil pressure warning a little while back. She has been using other cars since then, and it's been pretty much parked.

She told me it happened, usually, when she'd get off the highway. I figured out that the real key is that the oil has to be warmed up.

First step, replace the switch. So, I bought a new switch and an oil pressure guage and swapped the switch yesterday. The guage wasn't showing superhuman oil pressure, but it was a little over 2 bar at 2,000 RPM once the temp got up (the coolant was over 90 degrees, don't know how to make sure the oil was over 80 degrees - it was idling for about 15-20 minutes). I'd say it was at 2.1-2.2 bar. The bentley just states "at least 2 bar at 2,000 RPM.

So, I figure - the pump is good! Good news, probably just a bad switch. So I pop the new switch in, put everything back together, pull the car out of the garage and think - good to go. I start the car, let it heat up one more time, and as soon as you juice it to 2,000 RPM the light comes on.

One interesting note - when I had the manual guage connected to the car, the light came on when you juiced it to 2,000 RPM even though the sensor was not in the car. Not sure how this works, it's probably nothing, but the operation appears to be the same with the switch in or out.

So my question is - what next!? I know it could be a clogged pickup screen and the car has not been well maintained. But would I have 2 bar still?

If I drop the pan, the bentley has all these crazy instructions about putting the car into service position, draining the coolant, and disconnecting the A/C. - it looks like some things may have to be loosened and service position certainly isn't a big deal - but draining everything, especially the A/C seems unnecessary - my thought is I can fiddle with the pan to get it out without going nuts on moving everything....has anyone dropped the pan? How did you do it?

Finally, I am wondering if it is a problem with the wiring?? The car is also throwing codes in the vag-com for the MAF, both EGT sensors. The EGT sensors both read the same and after idling they are about 945 degrees. They were replaced within the last 50,000 miles, so I am doubtful the EGT is bad (maybe the MAF- there is also a rough idle that I can't figure out and the MAF is now reading 10+ g/s at idle).

Could a bad ground be the cause of all these problems?

Thanks for the help guys...

 

Most likely an oil pump failing or the oil pump pressure feed pipe o-rings are cracked or torn. You need to remove the lower oil pan to check these items.

Oil pressure switch is ground triggered when it hits 2 Bar I believe. That's why when the engine is revved with the oil pressure switch out, the oil light came on. It saw no ground signal when the engine was at 2k RPMs.

 

Do you know what the oil pressure specs are for a good pump? I know that Bentley states 2.0 Bar at 2,000 RPM - but I'm not sure how far from the "minimum" a normal car runs at?

My thinking is going like this. I believe the switch, as you suggest, is ignored below 1,500 RPM. I also believe the computer has 2 ways of monitoring this system - engine speed and pressure. When the switch is out, it only sees engine speed and no pressure - so it triggers the light.

When the switch is in, it acts EXACTLY the same way. I know that I am getting pressure, so I am hesitant to jump to the "bad oil pump" or even the clogged filter screen conclusion.

I've only seen 1-2 cases of clogged filter screens on the 2.7T on this forum, but maybe I haven't lookeed hard enough. On the 1.8T, it is rampant.

The audi dealership parts guy told me that he doesn't even stock the oil pumps because he never sells them - they just don't go very often. And by not often, he meant a couple times in the last 10 years.

The simplest solution here, that would make the car act the same with the switch in as with it out, is that the wiring is not connected - a break in the wire, bad connections in the plug, etc.

Does anyone know how to test the wiring? Is one pin 12V and the other ground?

 

Hook a electrical tester to the switch and see if it grounds itself around 2k rpm.

 

I don't understand why the oil pan cannot be removed with just the bellypan removed. The 4.2A6 oil pan drops easily with just the belly pan off.

 

It can.

 

My guess is that the instructions are referring to removal of the upper pan.

Any CEL or other issues?

I think the tester idea for the switch is a good one. It should close at 2 bar. Where did the new switch come from? Are you sure it is the right one? They all look the same but are internally different.

 

Ah ha. That would explain the service position, AC compressor has to be removed/hung whatever, lots of stuff fastened/impeding removal of upper pan.

 

Yes, maybe the instructions refered to the upper section - I would have thought the pan could have been just dropped in the A6 too.

The new switch came from the dealership. I didn't check, but I think it said 1.6-2 bar on the switch, I will check the old one when I get back over there.

No CEL, but I do have codes stored when I checked with a Vag-Com that show problems with the MAF and EGT sensors - forget the specific codes. I cleared them about a week ago and they were back this weekend. I think the MAF may be on its way out...it's reading over 10 g/s at idle. I know you need to test it under load, but I believe the MAF in my car (same car, but an 04 instead of an 01) reads 5-7 g/s at idle.

I agree that the tester on the switch is a good idea ...any instructions on how to do this? I should just put a multimeter to read 20V, find a ground, find a live 12V pin on the switch and then have someon rev and see how close to 0 it gets? It could be hard to get at that switch with a probe while it's in the car...