Josh B

Very frustrated this morning. Spent all day Friday and all day Sunday working on my car. Hoping someone on here might have an idea....

Here is a thread that I started a little while ago about my oil pressure issues.

https://rennlist.com/forums/924-931-944-951-968-forum/467123-oil-pressure-puzzle-arrrrgh.html

Cliff notes are that on my 87 944 turbo with 139k I'll have good oil pressure on startup and then after the car warms up at higher RPMS oil pressure will decrease. Normally my guage will show 2.5 bar or better at warm idle. Now after warm up and higher rpm driving she will show 2 bar at idle and maybe only 3 bar at running at 4k rpms. These numbers don't sound that bad but I've observed under acceleration the pressure going down - there has to be something wrong.

Before this past weekend I had changed out the sending unit for a known good used one, changed out the 1 piece OPRV for a known good used one, checked the 150ft/lb torque on the crank and changed the oil and filter.

This weekend I pulled the oil pan. The pickup looked fine but the seal looked awful. Also there were a couple broken pieces of baffle in the oil pan. Not enough to cover the pickup though. There were some odd marks in the oil pan floor.

I put a new seal on the pickup, installed a new pickup, new baffle and new oil pan gasket. Put in new engine mounts, sealed up the bottom of the turbo mount, and fixed my broken stud in the crossmember while I was at it.

Drove the car into work today and she is showing the same signs of lower oil pressure after warm up.

Here are some pics of the work. Emanuel in his white 951 did some work on his car too - Vitesse MAF and 55lb injectors - everything worked fine on his car.

Zero10

Old seal looks fine to me. I agree it wasn't your issue, and I do agree there is one. Once you pass 2000-2500RPM it should never be under 4 bar oil pressure.

A bit more history here, how old are the rod bearings? mains?
I have read in the past that dropping oil pressure under load pointed to either main bearing wear, or the thrust surfaces on the crank being worn down too far.

Josh B

Not that it made a difference but you sure the old pickup seal looked ok? That is it from both sides up next to a new one in the last two pictures I posted.

As far as I know rod bearings and mains are original to the car. I sure do hope they aren't the issue. I would be more tempted to buy a brand new OPRV valve before replacing them.

It is almost like the car will be fine at startup but then after running for a while something goes haywire and oil pressure drops under rising rpms. If I drive like a grandma or turn the car off and let it sit for a minute it will stay within more pressure parameters.

Techno Duck

Did you check for wear on the rod bearings by visual inspection or use of plastigauge?? That was an awful lot of work to go through and not do that.

Chris White

Check for a worn thrust main bearing. its the center main bearing, use a pry bar to move the crank foward and back and measure the amount of movement with a dial indicator.
Its not your OPRV - they either work or don't work, the fact that your oil reads fine when cold and drops when warm and accelerating rules out the OPRV. Also - if it were a pick up issue the problem would be worse at cold temps - harder to draw the oil into the pick up, any air leak will cause a loss of prime.

cruise98

Put a manual gauge on it before you panic. You could have a bad ground for the gauges.

You did not mention replacing the rod bearings while you where in there. Did you?

Josh B

Didn't replace the rod bearings or main bearings. Ugghhh - this is turning into a lot nastier problem than I suspected. I guess main bearings require pulling the engine eh?

Chris White

The only main that will show wear is the thrust bearing, change the rod bearings - if any show serious wear than you might think about the main. If hte rod bearings look decent then just swap those and be happy!

Josh B

Hi Chris - sure do appreciate all the advice - especially since I know you have put a motor or two together. How is it that the rod bearings and main bearings affect oil pressure - haven't been able to figure that one out yet?

Chris White

The gap between the bearing and the rod or crank is very small -as it wears the gap can increse allowing more oil to pass. If the gap between the surfaces becomes quite large it will allow enough oil to flow to lower the oil pressure.

F18Rep

Here's a quick check, might be a little difficult on a turbo... with the engine running, peek in at the crank's power steering pulley. If it is off-center (not mounted right - very easy to do) then it will be wobbling. If wobbling, you have found your problem. Just the first thing I always do for oil pressure problems....Bruce

JET951

listen to Keith. you may not even have a problem with your oil pressure.

porschefig

Check this one too!! BTDT

87944turbo

Josh, I second the mech. pressure gauge suggestions. I chased several "problems" that all ended up being related to the electrical gauge, never again. Here is what I purchased from egauges.com.

Zero10

Definitely check with a mechanical gauge before losing any sleep over this.

Engine must come out of the car for mains, since the crank needs to come out of the engine it requires removal of pretty much everything on the front and back of the engine. The job sucks