Checking Rear Main Oil Leak

[A-Man]

My 1930 Deluxe Coupe has a serious oil leak, which appears to be coming from the rear main area. As I have not tore this "stock" engine down (reported to have been overhauled when I purchased it about 10 years ago), I plan to delve into, searching for the cause. I should comment that the engine did not have a severe oil leak when I purchased it, and has become more severe as time goes by.

I have searched postings on this forum. I believe I have determined the leak to be coming from the rear main area. As I understand there could be many causes for the leak, however, two(2) appear to be at the top of the list - cap clearances on the crankshaft and/or plugged oil tube on the rear main cap.

I plan to remove the oil pan to examine the rear main, and have the following questions:
1) What is the best approach in looking at the oil tube to determine if it is plugged - removal of tube?
2) I also understand that the length of the oil tube into the oil pan is crucial. How is the proper length determine, if I have the oil drained from the oil pan for removal?
3) What is the best/proper way to examine the cap & crankshaft clearances? Ideally, I presume the cap should be removed. Can it be down without removal?

I have been using 30 weight oil. I have examined the oil filter cap and oil filler tube. I have even removed the filler cap(installed nylon stocking hose as a temporary cover) to eliminate/reduce internal oil pressure.

Thanks.

[VFRhugh]

Antique Engineering has a great write up on rear main leaks. Other than inspecting the rear main dip tube, dropping the pan isn't going to get you much. Although I don't advocate doing this oil can be seen running out the back of the rear main bearing cap with the engine running & inspection plate removed.
http://antiqueenginerebuilding.com/REARMAINLEAK.html

[Art Newland]

I took a good look inside a spare engine before installing it in my car a few months ago and documented the process in this thread;
https://www.fordbarn.com/forum/showthread.php?t=210059
Lots of pictures, The engine has nice tight clearances on the mains (.0015) and the thrust bearing is also in great shape. It hasn't leaked a drop of oil... only about 100 miles on it so far however.

[1955cj5]

Another source for what appears to be a rear main leak is the camshaft.

Unless it's been modified the cam is exposed at the rear of the crankcase and there is only a gasket between the block and flywheel housing that is supposed to keep it from leaking.

Cam is in upper right of photo..

In my engine the gasket was missing......It leaked a fair puddle every time it was parked.

This is covered in the antique engine rebuilding link above

[Chuck Sea/Tac]

VFRhugh: why don't you advocate removing the inspection cover ,run the engine and seeing if oil is getting past the bearing?
Art: did you do anything to the Y oil groove in the rear main?

[A-Man]

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Just want to say thanks to the above Model Aer's for their information! A-Man

[jfreddie]

I'm also a fan of watching the engine run with the inspection cover off.
Wipe off the area first and then start it up and watch where oil comes.
If it doesn't come out of the bearing housing area, then it may be from the cam.

[Art Newland]

Originally Posted by Chuck Sea/Tac

VFRhugh: why don't you advocate removing the inspection cover ,run the engine and seeing if oil is getting past the bearing?
Art: did you do anything to the Y oil groove in the rear main?

If you are referring to the extra groove cut into the main bearing cap, I left it as-is.

[VFRhugh]

I did it but it is a potentially dangerous endeavor. Just didn't want to encourage anyone to crawl under a running car. Had mine in neutral, butted up to my garage, double blocked wheels, & rear wheels off the ground on jack stands.
Hugh

[Dick Steinkamp]

Isn't there also a chance the leak is from the rear oil pan seal?

Relatively quick fix if it is.

[Mitch//pa]

I would ck for excessive crankshaft endplay. If it's out of spec just pull the mill no sense of busting your stones