losing oil pressure
 

2001 volvo s80 2.9 with no turbo

car has been a problem vehicle from the start.

had a problem a year or so ago. "Low oil pressure" message came up. Making a long story short, it looked like the engine had some signs of sludge. Did a flush, replaced filter, filed with oil and no more problems.

Fast forward to last week. Oil message comes on again. Bad leak at oil pump seen. Replaced pump. Also dropped pan, cleaned out, cleaned screen, sump, pick up tube, all gaskets and o-ring seals.

Pressure is fine, but suddenly, engine loses all pressure (0 lbs.). Turn off engine for 2 seconds, and re-start and pressure is back to normal until I drive the car for a few minutes at higher rpms, then loses all pressure again (instantly).

What could be causing this?

RE: losing oil pressure
 

Did you replace the pickup tube or clean it?
There might have been more sludge knocked loose and clogging the pickup tube.
Have been down this road before and had to drop pan about 7 times before getting everything out and the pickup tube was done getting clogged.

RE: losing oil pressure
 

Yes. It was cleaned, along with the screen. All new gaskets and seals.

I cant figure out why after the oil pressure is lost (zero lbs of pressure), all it takes is to turn the engine off, count to five, re-start, and the oil pressure is where it is suposed to be.

this is the baffling part.

any ideas?

its like someone flicks a switch and all the pressure is gone, in an instant. then, it returns and stays after re-start. problem doesnt reoccur until after driving it and bringing rpms up a bit for a few minutes. we verified this with an oil pressure gauge.

RE: losing oil pressure
 

I will bet the pickup tube is getting clogged.
Then when you turn it off it all sinks back down.
If you drain the oil and look through the drain plug hole you should be able to see the screen on the pick up tube. I will bet you will see a bunch of junk up there.

RE: losing oil pressure
 

wont the baffle block the view?

I just had the engine flushed again this afternoon. re-filled with synthetic. If the problem recurrs, I will see if my mechanic can save the synthetic and we'll try and peek to the screen. This was the exact problem we I had when I brought the car in. After dropping the pan, removing the baffle and completly cleaning it of any buildup, installing all new seals, pump and gaskets, cleaning the pick-up tube, etc, and re-flushing. The galleries to the top of the engine appear clear, as there is plenty of oil getting up there when the pressure is okay.

Could the o-rings be hosed or installed incorrectly, causing this problem?

If the screen isnt clogged, any other thoughts?

RE: losing oil pressure
 

If the screen isn't clogged I would look at the o-rings again.
But the way it sounds the screen is getting clogged.
I have seen this many times.
The stuff you can't see is whats breaking loose now.

We have almost stopped taking in cars that are badly sludged because of this.
We end up taking it apart on an average of 5 times to make sure it is all cleaned.