78SC - Oil residue in throttle body, plenum, and blow-off tube - how?

[Jdub]

Pop-off valve went off, so made sure to open airbox and inspect & clean. Know how much oil to put in, so halfway on stick - gauge measures similar. Why, then, when I popped open the rubber plenum over the throttle body/airbox, did I see heavy oil residue within the plenum all the way back via blow-off tube to the oil tank's filler tube?

Is it possible to take a curve so tightly that oil is pushed up into the fill tube, then into the overflow? Is 1/2 way on the stick still a bit too much oil?

FYI to anyone who has overfilled their oil on a CIS/SC, you are going to have to open the airbox to note oil residue, and if found, consider removing the plenum and checking for amounts of oil within the throttle body and plenum all the way back to the oil fill tube. Failure to remove and clean this foamy mess will mean a bad idling car as it attempts to consume all of this. I do not think this is normal - I think the overflow is just for that, and not for blow-by. If I am wrong, I am very ready to take in the collective knowledge.

[BoxsterGT]

Yup, Drop the level a bit. Probably smokes a bit too. We call it mosquito control when it smokes from too much oil in the system.

Sounds like you have been there before. Beautiful country out there. Enjoy the ride.

Len

[snbush67]

Originally Posted by Jdub

Is 1/2 way on the stick still a bit too much oil?

Yes, 1/2 way on the stick is still a bit too much oil, 1/2 way between the MIN and MAX marks is OK. Check with engine running at idle, operating temperature, parked on level surface.