My '85 has decided to mark it's territory. When I was replacing the starter, i got a better look.

The drip of course is coming from the lowest part on the oil pan and i figure the leak is either an oil pan gasket or a rear main seal.

Does anyone know a good (and easy) way to figure out which it is without pulling things apart? Does one leak have symptoms or visible signs that are different from the other?

I was thinking if it was a rear main seal, the drip would be more at the bottom of the bell housing but that's an untested theory.

Any thoughts?

 

The leak could be anywhere, even coming from up front. The air from driving blows the oil back and it hits the thing that hangs the lowest and then drips from there.

The best thing for you to do is clean the engine up as best you can, and let it sit in the driveway and run, and then check for leaks, don't drive it. It may be a slow leak though, and if it is, you may have to go ahead and drive it, but check the engine over frequently after you have cleaned it up. Even experienced mechanics have a hard time finding leaks, so you will have to be persistant till you find it.

 

In addition to doing some scraping and cleaning you might also try checking / tightening all the bolts around your oil pan and valve covers.

Don't be surprised if you find some loose ones.

 

There's a little slot cut into the bottom of the bell housing where you can see the flywheel gears. If it's the rear main leaking, there's a good chance you can shine a flashlight in there and see oil.

On mine, the oil drips out of this hole, and you can see a small pool of oil collecting through that access hole.

Just looking at the outside of the engine won't tell you much, as someone else suggested, the air blows the oil EVERYWHERE. On my truck it even looks like the tranny / transfer case is leaking, but it's just the oil that gets blown back while driving. I have to add a quart about every 1,500 miles, so I've learned to live with it until the weather gets better and I can tear into it.

 

A lot of people think their rear differential is leaking, but it's really oil blowing back from something up front and hitting the diff and running down off the bottom of it.

 

True statement, before my rebuild, this very thing happened to me. I cleaned up my rear diff since the rebuild, and I haven't had a new drop of oil from the rear diff at all.