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
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86 325e
80 911 SC
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