You are here:

Classic/Antique Car Repair/31 Coupe leaking oil out rear main


We have a 1931 Coupe that was leaking oil out the rear main. Have read through several posts regarding this issue, but still need a bit of extra advice.  We started with basic tests, made sure the oil fill tube was open. Oil was dripping off the bolts on the rear main. Dropped the pan and checked the oil tube on the rear main and it is open. Oil slinger looked good. Replaced shims on all three mains and all are approximately twenty-thousandths. We did not pull the engine, but used the old method of removing the shims from each cap, replacing them with new ones and removing them until the engine couldn’t be cranked. We then added one more shim until the engine could be turned. Torqued all main bolts to 80 lbs. Oil seems to be running out more now than before. Any suggestions?

Wow, it sounds like you know what you are doing and you have done all the right things. I assume you put in new rope seals, top and bottom.  Make sure the oil is not coming from the front of the crank and dripping down in the rear of the pan.  If your engine is 100% model A original, it should not leak very much oil, but it will leak a little.  We have had some rebuilt engines where "improvements" have been made in the rear main area and no one can stop the leak.  Hope that is not your case.  I'll ask my friends and see if they can offer any suggestions.  Remember that the bearing is outside of the pan and that slinger and tube were designed to get most of it back into the pan.  Someone may have made some changes in that area, mixing new and old methods and screwed it up.  The book says two things that could go wrong.  If the oil tube is screwed in too far, into the cap, the end could get blocked.  And be sure the shims are against the crank bearing surface.  I assume you have Les Andrews Red book.  Sorry I can't help you, but let me check around.  If you figure it out, let me know what it was.  jack  

Classic/Antique Car Repair

All Answers

Answers by Expert:

Ask Experts


jack bahm


Only repair type questions on the 1928-1931 Ford Model A.


Owned one when I was 15 yrs old, and now have owned 5. Still own and play with 2 of them.

Oakleaf region of MARC. Model A Restorers Club. I have put several Model A videos on the Oakleaf site that may be of help. Things like how to start the A, how to Time it, how to troubleshoot it.. Go to and you will find them. Also, go to and search for "jackbahm" and you will find over a hundred videos. Many about the Model A and our outings. jack

"More than you need to know about cars." Just a small book for Car Nuts. "Model A Ford Tips and Hints" "Get A Horse" (What to do when Henry's Lady quits on you.) or Snyder's Antique Parts. "Engineering Stuff" (For the Kid who likes to take things apart and get them back together). Kids book for ages 10-16. 2012 Many Model A movies that can be found on

BSME LSU, 1958, Masters of automotive engineering from the Chrysler Institute of engineering, 1960, MBA Mich State, 1976. Worked as an engineer at Chrysler from 1958 to the end of 1991.

Awards and Honors
Two patents while working in auto industry. Go to this site for my Model A videos.

©2016 All rights reserved.