Searching for source of oil on back of car
 

Hi Folks:

My '78 911SC track car is coming home from a weekend of fun with the low pressure areas behind the engine covered in a oily dirty mess. I've gotten comments from drivers and corner workers that the car smokes occasionally but I've never observed this when the car has been driven in the paddock or on track.

I just did a compression test to check if I broke a ring or something. Results: 1,2,3 @ 135 and 4,5,6 @ 140 - seems ok. Anything else to look at/for while I'm in there?

The engine is two seasons old. A 3.2SS using Carrillo 9.5:1 pistons and Mahle cylinders, a Knight M1 cam and stock CIS intake.

Any suggestions on where to look next? I've wondered if this could be an oil breather issue but don't know how to troubleshoot that. I run Mobil-1 15/50 oil at the min mark on the dipstick so this shouldn't be an overfill problem.

Thanks,
-Vic

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Possibly the crankshaft seal ( behind the crankshaft pulley) .

Interesting - I didn’t think about external leaks (hence my post here thinking this is more of a rebuild topic). As for the seal at the rear, the “cup” under the pulley doesn’t look wet so I think it can rule that out.

Thanks for your the suggestion. I guess the transmission is in play too. That was also rebuilt and has shown some signs of leakage.

Vic

Re oil breather issue: I think that's doubtful. The breather hose from the top of the engine goes 20" or so to the oil tank then a separate hose goes from the neck to the intake boot. Not much oil makes it that far. If you have re-plumbed the breather hoses then it may be more likely.

Oil leaks: If oil is getting onto the hot exhaust pipes, then yes, you need to find and eliminate those.

Oil past the rings or valves: If this is a serious track car and you flog it hard, more oil may be building up in the case, getting splashed and flung around, and getting past the rings, especially on overrun. Next time you're at the track, ask the corner workers to tell you when they saw smoke. Was it down the straight under full throttle? Or in the braking zone, or in the turns, or randomly everywhere?

Thanks for the above thoughts. My season is over so it will be a while before I can ask corner workers for help identifying the smoking.

I may have found one cuplrit for the oily back-end: my transmission was overfilled during the last rebuild. I pulled the fill plug and 1+ cups of oil drained out. Hoping this fixes things but as noted above I won't know until spring.

-Vic

Regarding tranny… Is the bell covered with oil?

Yep, tranny is covered in oil. I made a note to check in the spring that the vent is oriented correctly.

every 911, 964 or 993 w/ a rear spoiler that I have driven collects that oily residue,

Thanks, Bill. Agreed this low pressure area collects grime. My issue is it’s way worse than prior years (I’ve been tracking this car since ‘95). My fingers are crossed that the tranny played a large part in the greasy dirt deposits. The photos don’t do it justice but I literally scrape this stuff off with paper towels before washing the car after each event.

I agree with Bill, my track car had no oil leaks, front tank with breather going all the way forward and back to engine compartment, I always figured it was oil coming out the exhaust, In spit of minimal oil consumption. It’s normal to me.