Hi all, I have been having a low oil pressure problem for some time now. It seems that when the motor and oil are warm and the car is running at idle speed (approx. 900 rpm) the central warning indicator starts to blink warning of low oil pressure. When the motor is reved to about 1200-1400 rpm the indicator shuts off but reappears again at idle speed.

I have removed the oil pressure sensor, cleaned it and put it back together and reinstalled. Is the warning indicator linked through the oil pressure sender or is it just for the guage in the pod. By the way, the gauge in the pod stays pegged at 5 bar when running.

Or does the central warning indicator pick up a low oil pressure problem from a different sensor? If the sensors are working correctly and I do indeed have low oil pressure at idle how would I fix that? New oil pump?

I have been working on this problem for some time now and dont want to spend unecesary money on parts that are still good.

Thanks for your support and keep'em running.

 

Oil pressure is considered normal if it is above 1 Bar at idle and over 4 Bar at 4000 RPM. Mine usually registers 1.5 bar at idle and 5 Bar at anything over 2000 RPM. YMMV.

If you are getting a warning even though the oil pressure is within spec, replace the sender.

 

If it helps, im pretty sure the oil PRESSURE and the oil WARNING are on two different circuits. <img src="confused.gif" border="0">

 

Yeah,that restricts the argument....My S2 sits conntinually at 3-

N!

 

Curt,
Better to check the actual oil pressure with a good manual manometer installed where you have your oil pressure sensor?
You only have this one sensor, i.e. that's giving the signals to the instrument and to the warning light.
See Shop Manual page 17-9 - Here you can see how to install the manometer - They also give the minimum oil pressure:
700-750 RPM min. 1.0 Bar (28 PSI) - 4000 RPM min. 5 Bar (70 PSI)
If you are using a very thin oil today, you can try with a higher grade.

 

Tony, I followed your procedure to cleaning the sending unit, however, it didnt correct the problem. Im thinking that I will just buy a sending unit and see if it works. I hate doing stuff like that without knowing for sure. It seems like one could waste a lot of money using trial and error to try and fix a 928.

 

Okay, lets say the sender is fine and my gauge in the pod is just screwed up. How would I fix a low oil pressure problem at idle?

Ive had the oil pump out to replace the "O" ring last time I did the timing belt. At that time it didnt look like that thing could fail, but maybe it wears out enough to have a low oil pressure problem at idle.

 

Curt - before you toss money at the sender, try Erik's tip about checking the true pressure with a mechanical gauge installed into the sender area. Electric gauges are notoriously inaccurate and you may be chasing a non-existant problem.

If it is truly low oil pressure, possible sources are low volume from the pump, an open oil pressure relief valve, or (eeek) large bearing oil clearances.

good luck

 

Thanks James you give great advice. First thing for sure I will get a guage and check it out. Hopefully that will give me some answers.

The engine itself sounds really good and runs just as good as it sounds. No noisy nocks or anything either when its hot or cold.

Im just trying to get every little thing in working order on this car. Most older 928's have a lot of little things that dont function correctly.

A list of things that I need to correct.

1. Low oil pressure prob. or guage problems.

2. Vacuum door locks almost function correctly. I think the passenger side mechanism is sticking.

3. Headlight height manual adjusting for my euro car. How do you add fluid and where do you add it.

4. Windshield washer wont spray. Possible motor or dirty wire connection.

5. Headlight washer wont spray. Same as above.

Thats it for now. Everything else works!!!

 

Curt,

You mentioned that your gauge stays at 5 bar all the time. If it stays at 5 bar at warm idle, it appears that the gauge portion of your sender is bad.

Concerning the 1 bar of pressure at idle. Since the 928 sender is at the pump, shouldn'the pressure be higher than most engines where the pressure is measured at the head?

Dennis

 

Duh...I didn't even notice that. I'll betcha the 5-bar pin is because you switched the two connections from the sender. Happened to me about a dozen times

Switch 'em around and see what happens.

Oh, and a question for the lubrication gurus out there (you know what I mean ): it's my understanding that the oil pump is positive displacement, as in it only moves volume of oil - the pressure itself is created by moving that volume through smaller passages (oil galleries, bearing clearances, and so on) similar to sticking your thumb over the end of a garden hose. The pressure sender then measures the pressure of oil returning from the engine. Correct or no?