I'm about to dive into the 1.8 motor for the first time, and am wondering if there is an oil pressure relief valve, and if so, where it is? I was thinking that dropping the oil pan would be a breeze, but according to the Bentley manual, I'm sadly mistaken.

And a search of the Bentley CD doesn't return anything specific about an oil pressure relief valve.

Thanks for any guideance.

It figures that as soon as I post this, I'd find what I'm looking for.

It appears that the oil pressure relief valve is indeed under the oil pan, on the oil pump cover.

With that said, has anyone heard of the pressure relief valve failing/sticking open/etc?

I've not got a pressure gauges installed yet, but the idiot light taunts me from time to time. More often than not it's after I've pushed the motor beyond 5k rpms (as in merging onto the freeway). If I'm gentle on it (shifting before 4k) I seem to be in an 'idiot light free' zone.

Again, thanks for any input.

If I were you, I'd buy an oil pressure sender and gauge to get an idea of what the "true" oil pressure is. With cold (50F) 10W-40 oil, oil pressure in the 1.8T will run between 4 and 5 bar (58-72psi) at idle. As the engine warms up, this will drop to ~2.5-3bar (slightly less with a 30W oil).

It's possible that if the on/off ramp is steeply banked (enough to allow you to comfortably take it at 20-30mph over the posted limit :-)) you could be moving all the oil away from the pick up momentarily. I'd guess this might be the issue if it only happens during hard acceleration or after a high G maneuver. If it bothers you, try running a 40W or 50W oil.

Don't trust the dipstick to tell you, change the oil, and then double check the level on the dipstick.

Oil thins out over time, so if it's old, change it. Also, what type of oil are you running?

When most cars have oil pressure problems, it's because of high mileage wear on the bearings, causing low pressure at idle, but once the RPMs pick up and more oil starts flowing, the pressure is fine. Running a slightly thicker oil will help with this situation.

This is not your situation though, it definately sounds oil-pump related. It could be a bad pump, or a partially blocked inlet for the pump (bad) or possibly a toasted bearing (worse)

It is VERY bad to have low oil pressure under load. It will get worse. The idiot light triggers very low, like 5psi or so. This is not enough oil pressure at higher RPMs, and for all you know, maybe you only have 10psi at 4k RPM.

Install an oil pressure gauge, or start saving for a new motor.

No - I changed the oil as soon as I took posession of the car. I'm pretty sure it's the oil pump, as I'm hearing what can be described as a "low power steering fluid" pump moaning.

I'm going to go ahead and order an oil pump / cover / relief valve and pull the pan off next weekend.

Which bearing are you referring to? One of the mains? If not, which?

Thanks.

If theres too much clearance in the bearing, more oil will come out of it instead of the others, causing a drop in pressure.

Found out the car has an "Audi Assured" extended warranty on it - for another 1300 miles. :)

I sent Audi a check to xfer the warranty into my name, and they took care of me. Got the car into a dealer the day after I found out about the warranty, they went over it w/a fine tooth comb, and after a $50 warranty payment the car has a new oil pump.

Now I'll feel better about even thinking of modding the car...

Oh yeah - I'm pretty happy with the way Audi took care of me. Now to slowly start turning the car up.. :)