BAMvette

Hi!

I'm trying to diagnose an oil leak on my '81.

Each time I drive it there is a .25 cent sized drop of oil on the garage floor.

From under the car, I can see a single drop of oil forming, getting ready to drop, on the drain pan plug.

I'm thinking rear main seal, and have read all the 4 pages of results from a search there.

Before I attack the seal, does anyone have additional diagnostic techniques or places to look?

As near as I can tell, the distributor isn't leaking, nor is the intake manifold.

From under the car, I can see wet oil coming from above the driver's side head, at the very rear of the head/block. Can't see it from above.

What's in there that might leak. Just the valve cover gasket???

Auto tranny, BTW.

Thanks!

[Update]: I just removed the inspection plate from the bellhousing. The front of the plate has NO OIL on it at all. Seal does not appear wet to me. The rear end of the oil pan has caked-on gunk.

tomgallucci57

im definetly no expert,but i would tie a small rag to a thin stick and from under the car ,try and wipe off the oil,till its sorta dry,then drive it abit and look back up there to see if its wet again,,if it is,then hopefully its just valve cover gaskets,,tom

Lon Wayne

Valve cover drip comes out on the side of the motor go ahead ask me how I know . ( cause both of mine needed replaced ) and either the head is leaking or I still have A small leak Heck Its Just like A Harley arent they supposed to leak oil??after 35 years.
Sounds like the rear main seal!

CoolShark

I had the plastic washer around the drain plug crack and had a small leak.

BAMvette

Thanks for the thought.

I've had that happen on another vehicle. I'd be tickled if that is the problem.

This 'Vette is new to us and I'm still learning it's quirks. Haven't changed the oil yet, but it's on my list, and I'll be changing out the plug and and the washer, if there is one. I don't know if it's SUPPOSED to have one or not. Doesn't look like it's got one now.

Any other ideas, guys? Again, with the inspection plate off, the rear main seal looks dry, and the flex plate definately is.

Skip Burney

what about the rear intake seal

noonie

Oil can come from almost anywhere, but the most common by far is the front and rear seals, then the valve covers.

Best way to test is to degrease the engine and then put powder on all the areas, it will show up exactly where the leak starts. An old squeeze bulb works well to apply. It's also easy to hose the powder off afterwards. Easier than the dye tests.

PRNDL

This is probably not your problem, but...

I had an incredibly annoying little leak at my drain plug. I changed the washer several times, tightened the drain plug as much as I dared without stripping the whole thing, changed out the drain plug, tried teflon tape on the drain plug, and was tempted to try an oversized plug. Well, finally after wiping off the excess oil (over and over again) and looking very carefully I noticed a little crack in my oil pan right behind the drain plug, so the little drips of oil were not coming from the drain plug itself, but out of this crack right behind the drain plug.

I was actually able to repair the crack with some JB weld. (sanded well and repainted with engine orange)

BAMvette

Dry, as far as I can see!

My valve cover is certainly suspect. Degreasing the back of the engine block would be tough, I'd think...as well as tomgallucci57's trick....I'll take a closer look at it next time I get it up on ramps to check the leak's progress after today's work.

VERY interesting! Sounds like bubba was there before ya and over-torqued the plug. I'll keep that thought in mind as well.

THANKS to all of you!

G-Sting

If it ends up being a valve cover leak, I have been extremely pleased with the Fel-Pro Perma Dry Plus gasket set. Someone else recommended them here. After completely cleaning the valve cover and head, they were installed dry (as recommended) with normal valve cover bolt torque. They have stayed dry as a bone.

BAMvette

Mine has the old school cork gaskets in it now. I can see 'em from underneath the car. I've never liked those things since 1975.

I'll keep your suggestion in mind.

Thanks!

Paul L

Get some fluorescent dye from your GM dealer (or other store), drop it in the crankcase, take a drive, and do an inspection with a black (UV) light.

3JsVette

Exactly. Do a complete clean up - add the dye - off you go. You will be amazed what the black light will show.

tailskid

I just went through the same thing with my 82' a couple of months ago. I was afraid it was the rear main also, until I got under the car and had a good look around. With only 42000 miles the car sits alot and the gaskets were dried out. Ended up changing the valve cover, pan and tranny gaskets and it's dry as a bone now.
Good luck.