VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 36 oil leak

The original 206 motor was just rebuilt (top and bottom). There is a fair amount of oil leaking out the back of the motor and dripping out the bottom of the bell housing. It does not show that it is over filled with oil.

What could be the problem?

Hi There and welcome to Chevy Chatter II. Glad to have you with us.

There are several things that could cause the oil to leak out of the rear main. However, first you might want to take your engine back to the machine shop that rebuilt the engine and have them check out the problem since their work should be guaranteed.

Hi Junk Yard Dog

I had to have it towed back to the shop today for a different reason(fuel system) so,hopefully,they will fix it. I'm told there is not a rear seal in these motors and am wondering what might have caused the leak

You are correct there is no seal and none is needed. You have a slinger built into the crankshaft that slings oil to a groove which channels oil to the drain.

Have them check the tolerance on the rear main bearing. It must be 0.001-0.0015" If over 0.0025" it will leak oil. Another thing to check is the passage on the rear main cap that drains oil back to the pan. If it is plugged or restricted you will have a rear main leak. Lastly if the rear main bearing is tapered, it can leak. Or if they didn't check the crank to be sure it was not bent then it will taper the rear bearing and make it leak. There are a few others but those are the most prevalent.

Let us know if they check all of the above and it still leaks.

Chipper, Thank you for the info. I'll let you know.

We have found that usually local machine shops don't have much experience with the old babbitt engines and they sometimes don't get the tolerances correct....among other things. A rear main leak seems to be a common problem with engines that were done at local machine shops. At any rate, Chipper gave you some good things to look for and hopefully those suggestions will help.

Another thing to look for is the back of the valve cover gasket leaking. Chances are that is not your problem, however, when the back of the valve cover leaks it appears to be the same as a rear main leak on the bottom end of the engine.

Let us know what you found out.

Junkyard Dog, Thanks for the help. I'll let you know

Also check for excess crankcase pressue due to breather restricted. Also rings may not be seating.

Or the back of the valve cover leaking.
Or the lower rear corner of the push rod cover leaking.
Or the end cork seals on the oil pan leaking due to incorrect installation.
Would vote first for the rear main leaking due to several reasons but these more minor and easy to check things should be inspected first.
The fact that the engine uses no rear main bearing seal will not be the problem if everything was done correctly.

Chev Nut was correct. It seems the lower rear corner of the push rod cover was the issue. Getting it back Friday. Looking for my first G&D soon.... since I rejoined the club

Thank You

It seems the lower rear corner of the push rod cover was not the only leak. Oil is still coming out of the bottom of the bell housing.

If the leak is from the rear main, would the oil pressure read low? The inside gauge reads just below 15 when warm at idle.

A leak at the rear main will not affect the oil prssure reading.
The normal hot oil pressure on a 1936 would be about 12 pounds at 50 MPH and 2 or 3 pounds at idle. Your engine may have a later gear type oil pump conversion.
There are several things that can cause the rear main to leak and some leakage could be considered normal.

Did you check to see if the back of the valve cover is leaking? Also, did the machine shop check the rear main clearances when you took the engine back to them?

ChevNut, Thank you for the reply. It sure seems more than normal. It's leaked about 1/2 a quart in the short time it's been back (<200 miles)

Junkyard Dog,

The valve cover does not appear to be leaking. They have not checked the rear main ....YET

I just sent you a PM.
Richard

PU Guy- Replied