80 SC 3.0--Oil circulation question/problem

I have an 80 SC in stock configuration. The engine runs great with no problems until you get aggressively on the throttle. Then the engine temp rises very quickly.

I **think** have narrowed the problem down to oil circulation. It appears as though the scavenge pump cannot keep up with the pressure pump. What I am finding is that under acceleration (or just reving the engine) the oil tank is very quickly sucked dry. Continued hard driving past this point
results in a marked drop in oil pressure and immediate rise in engine temp. At this point the pressure gauge is reading well below the 1 bar/1k rpms and in fact starts bouncing off Zero. Let car idle for a minute or
two and the tank fills back up, pressure goes back up and temp slowly starts to decline. My oil level gauge appears to be functioning normally and is quite accurate. When it is in the red, I verified with the stick that the tank was bone dry. Gauge at the top, stick says MAX. This was at OT.

Now originally I thought this was easily explained by a severe kink in my aux cooler line. Would make perfect sense, except for the fact this behavior also occurs well below OT. Also did not improve when I "fixed"
the kink. Which rules out both coolers and thermostats which I verified are working correctly. By the way, the internal cooler stays very cool, under 100F as verified with my temp gun. But as soon as the oil reached
OT, that sucker got real hot…about 175F. So the cooler does not "soak" up much radiant heat probably due to the continuous flow of cool air through it which makes it easy to check the thermostat.

Anyway, where the heck is the oil going? The only explanation I have is that it must be pooling up in the crankcase. Now…why can't the scavenge pump keep up? I checked all the other lines for kinks and found none. I
replaced the oil filter hoping that would be an easy fix…it wasn't. I am wondering about the sump screen (which I cleaned 800 miles ago), the pressure relief valve and safety valve, and the oil tank it self. I pray
to God it is not the scavenge pump itself…and how would you test it anyway?

Is it normal for the tank to be dry while at OT while accelerating?

Thoughts???

Ron Milliet
Petal, MS
87 325is http://www.dcslink.com/bmw3/index.htm
86 325e
80 911 SC http://www.dcslink.com/porsche/index.htm

I had a similiar problem on my 3.0. There was a Special Bulletin put out by Porsche years ago to correct this problem. It consists of changing the sump screen and the two springs and "pistons" in the bypass and relief passageways. Not sure if your engine is included in the bulletin. I think that it was for '78-79 engines. Not sure, can't remember. I think one of the ways to tell was if your drain plug on the sump was an allen bolt, then it needs the update, if it is a normal bolt head, then it does not,.. Sorry, can't remember.
Marc

First off, was this happening prior to you cleaning that screen? That's where I'd start. The orientation of the sump is also important. It should face the driver side IF you have the updated style of "anti-caviatation" sump pickup setup.

Please see the mail I have sent you.

Jw

Get rid of the loop oil cooler !
I was having a similar problem, high heat at high speeds.I went with a 19 row Mocal radiator cooler with manually controlled 7" Spal fan.BIG difference,problem solved !

Ron,

I think your system is similar to the 78-79 SC's. There is a spring under the engine that acts as a relief for the pump. It has a screw cap and when you remove the cap, the spring is right behind it. Don't know if this is the problem.

The other spring is located in the bypass for the oil cooler. Oil comes from the engine and is pumped to the bypass which is in front of your rear passanger side wheel. This allows the oil to return to the storage tank and then back to the engine.

If the spring in the bypass is weak, than it would allow more oil to return to the tank and your pressure would be low.

On the other hand, if the relief spring was weak, it would allow the oil to remain in the engine and not circulate as it is supposed to and naturally, it would get hot. Check both of these out. You may find that there is a broken spring.

Steve

***PROBLEM FOUND***

Thanks for the help. I found the problem and it was the SCREEN!! I am sorry to say that it was totally self inflicted. My car has the updated screen as installed on 80 and later models. The one with the solid top and mesh sides. Well…I managed to install that sucker wrong while I still had the engine on the table last fall. I “missed” the hole with the scavenge tube and had the plate installed in the wrong position. The plug should have been at a 90 angle from centerline nearer the left rear wheel. I had it in-line with the case seam nearer the muffler. The result of my folly is a destroyed screen and damaged pride. Hopefully no metal bits made their way into the system. The magnetic plug was clean as a whistle.

Anyway, I removed the damaged screen and reinstalled the sum plate. Filled it back up with oil and took it for a spin…PROBLEM SOLVED! Today I will break out the check book and order a new screen.

B I G thanks to all those that replied!

Regards,

Ron Milliet
Petal, MS
87 325is http://www.dcslink.com/bmw3/index.htm
86 325e
80 911 SC http://www.dcslink.com/porsche/index.htm