Well..... to make a long story short. After replacing my rear main seal and oil pan with the felpro one piece seal I have a worse leak then I did before on the inspection plate of my tranny.

It also looks like I have some sort of antifreeze or condensation that has mixed a little with the oil. It is difficult to tell where it is coming from but could use some guidance on how ot hunt down leaks on the back of the motor.

The car runs great, doesn't miss and hasnt overheaded. It was hot here last weekend when I drove it but the temperature never got above 230 on my sweep gauge. Never went above half on the dummy gauge. (boiling point for water is aroudn 250 degrees with a 14psi radiator cap)

My plan is to clean off the garage floor and the car tonight and then go for a drive and see if I can find the source of the leak. I have felt and looked around the heads and intake and have no trace of any fluid there.

What should I do? I'm almost thinking that once piece seal doesnt have enough flexibility to account for my 50 year old and not perfectly straight oil pan. That still doesnt account for the antifreeze. My fluid level in the radiator is lower now that the car got up to temp. Do you think I'm seeing two separate things mixing or is the problem something else?

 

I've never used this trick but have been told to use it to hunt for leaks. Wipe some of the grease and oil but not all off the bottom of the engine and then throw baby powder on it. Get it covered as best you can and then go for your drive. Don't go too long or too fast. When you get back, if there is a leak, the powder will show you where it originated as well as its path.

You'll have to wipe down the engine to get rid of the baby powder when your done, but it shouldn't take long and if you found the leak it's worth the 5 minutes I'd think. Like I said, been told to do it, never had a leak that difficult to find (crosses fingers).

Hope this helps.

 

I did the baby powder trick as well to find a rear main leak...You also need a mirror to look closely at the rear of the cylinder heads..The oil can run right along the seam of the cylinder head and block and then down around the back..This is true for intake gasket leaks as well.......You didn't give any info on your engine?...I am assuming its a 5.0 since you said it had a one piece seal?

 

I will get a mirror. It is actually a 68 302 block. The oil pan seal is once peice, the rear main is a 2 piecer.

 

So, were you able to isolate?

 

I may use the baby powder trick, I have a tiny leak (just a few drops a day) that I can't find.

For yours, I'd definitely look at the back of the heads and manifold like frdnut said, a leak in the rear rail of the manifold can fool you into thinking your rear main is the problem. Hopefully you didn't go through all that for nothing.

 

Well, it looks like I got the leak fixed with what I expected was the problem.

I ended up changing the oil pan gasket back to the original style 4 piece seal. With a light coat of silicone on each side of the cork portion of the gasket I have had essentially no leak!

Thanks for the help.

 

The bolt holes in oil pans get bent inward towards the block because of over tightening. It's a good idea to use a straight edge and a small ball-peen hammer to make them flat again before you put the pan back on.