Gentlemen,

Need some of your expertise.

My '76 High-boy has an oil leak. Not your straight forward, consistent, oil leak, but rather a leak when parked on a nose up angle. Does not leak beyond an occasional drip when parked on the almost flat street, nor in a nose-down position in the driveway.

The leak is dripping down off the mid-frame cross member, just below the bell housing. I've crawled around under there and cannot, with any confidence, determine the source. I replaced the right side valve cover gasket a month or so ago, and did not tighten one of the bolts adequately. That has been rectified.

I have an idea of the some of the obvious sources; rear main, etc., but would like to hear y'all's opinions on other possibilities, PLUS what order should I investigate these possibilities? Level of effort involved in each?

Thanks for your time and help.

Mac J.

 

Rear main seal I would expect leakage during engine operation, not when parked. But it's not impossible.


My first suspicion would be the rear portion of the oil pan gasket - parked nose-up, oil in the sump could maybe be pooled high enough that the gasket is submerged on some hills. Oil pan gasket can be a PITA with engine in the truck, unfortunately... Next in order of likelihood would be maybe valve covers - much easier to get to, but shouldn't have much oil available to leak unless drain-backs in heads are plugged. Intake manifold seems unlikely, as oil shouldn't really be pooled there either.

 

Thanks, Brian.

I'm degreasing the whole under side and engine this weekend. Maybe that'll she a bit more light on things.

I'm curious as to why the oil pan gasket is such a PITA? I've looked at it several time and it just doesn't look that difficult...even for me! What am I not seeing?

 

"Looking" at it and taking the oil pan off and getting the seal back in correctly and the pan back on is way different story. PITA

X2 on sounds like rear main, PITA again.

 

Oil pan gasket isn't bad at all if the engine's out on a stand. Dropping the oil pan with the engine in place, though, is generally a pain. Rear main seal is worse, of course, since you have to remove either the engine or transmission to get to it.

 

You guys are just full of good news, aren't ya!

Rich, regarding the oil pan, I know it's way different to look than to do, but what makes so difficult once you get the bolts out?

 

Its not a one piece gasket all the way around like a valve cover. The ones for the front and rear of the crank are curved and 2 piece if I remember right???

And doing is with the motor installed is a PITA. With it on a stand and turned upside down way more fun. I did one with the motor out of the truck and hanging from a chain hoist and was still a PITA.

 

Though, depending on your engine, FelPro does sell one-piece rubber oil pan gaskets that are easier to deal with. Check Rock Auto...