Weird Oil Leak

[ModelAMadMan]

I searched the forums and couldn't find anything that directly relates to my problem. I had my engine rebuilt not too long ago and I have had a pretty good oil leak. I contacted the rebuilder about it and he kept on coming up with lame excuses and it's gotten to the point where I don't want him touching my car anymore.

Here's the problem. The oil leaks out of the hole where the cotter pin is with a thin steady stream. It will not leak just idling, it will start to leak after driving it around a few minutes. I took the fill cap off and drove it around and it stopped leaking after driving it around but now only if it's on flat ground. When I pull up into my driveway on a small incline, the steady stream starts up again.

I have a little bit of mechanical knowledge on the Model A but not much. So hopefully this is an easy fix or someone would be kind enough to explain the steps how to fix it. Could it be as easy as having too much oil in it??

[J Franklin]

Search rear main oil leak for lots of information on what might be going on.

[fiddlybits]

rear main drain tube too short or missing

[Bob C]

Start with the easy stuff first--What is your oil level?

Bob

[hardtimes]

Welcome !
Well, couple things that I'd check, and the first would be in this order:
1- filler cap for proper venting;
2- level of oil in pan, run engine a quart low on dip stick to see if maybe is being run TOOO full ;
3- was the gasket which is between flywheel housing/block installed;
4- did 'builder' install a rear main seal .

If you do not 'know much' about Model A engine , who installed in car and attached flywheel housing to engine ?

[Purdy Swoft]

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The oil pump pumps the oil up into the valve chamber where it flows to the main and cam bearings by gravity. When the engine is shut off oil remains in the valve chamber untill it can slowly flow to the bearings. There is a slinger that is part of the crankshaft and rides inside the rear main bearing . When the car is parked with the front end uphill the oil in the valve chamber continues to flow by gravity untill the chamber drains and can and will flow right past the oil slinger on the rear of the crank shaft . When this happens the oil collects in the flywheel housing and drips out the hole in the bottom of the housing with the cotter pin . Also, if it leaks less with the oil filler cap removed, this indicates that the oil cap is restricting breathing inside the crankcase and allowing poressure to build up. There can be other problems but I will leave that for others.

[James Rogers]

Originally Posted by Purdy Swoft

The oil pump pumps the oil up into the valve chamber where it flows to the mainand cam bearings by gravity. When the engine is shut off oil remains in the valve chamber untill it can slowly flow to the bearings. There is a slinger that is part of the crankshaft and rides inside the rear main bearing . When the car is parked with the front end uphill the oil in the valve chamber continues to flow by gravity untill the chamber drains and can and will flow right past the oil slinger on the rear of the crank shaft When this happens the oil collects in the flywheel housing and drips out the hole in the bottom of the housind with the cotter pin. Also, if it leaks less with the oil filler cap removed, this indicates that the oil cap is restricting breathing inside the crankcase and allowing poressure to build up. There can be other problems but I will leave that for others.

Actually Purdy, you are correct in all you post except one thing. The oil will flow past the slinger and collect in the front of the flywheel and scare the daylights out of you if you don't know this. It will soon stop if the bearings are in spec and the flywheel empties.

[James Rogers]

Originally Posted by ModelAMadMan

I searched the forums and couldn't find anything that directly relates to my problem. I had my engine rebuilt not too long ago and I have had a pretty good oil leak. I contacted the rebuilder about it and he kept on coming up with lame excuses and it's gotten to the point where I don't want him touching my car anymore.

Here's the problem. The oil leaks out of the hole where the cotter pin is with a thin steady stream. It will not leak just idling, it will start to leak after driving it around a few minutes. I took the fill cap off and drove it around and it stopped leaking after driving it around but now only if it's on flat ground. When I pull up into my driveway on a small incline, the steady stream starts up again.

I have a little bit of mechanical knowledge on the Model A but not much. So hopefully this is an easy fix or someone would be kind enough to explain the steps how to fix it. Could it be as easy as having too much oil in it??

Sounds like one of two things has happened. One good, one bad. The drain tube may have fallen off the rear cap or someone cut it short and crankcase pressures are forcing oil past the slinger, easy fix. The other (bad) is the rear main bearing has failed in some way such as the thrust has broken off and the crank is moving to and fro or the bearing has been cut incorrectly and the thrust is too wide. The thrust clearance is supposed to be .004-.012.

[Brian T]

The original posters symptom is exactly what I had with my engine, I was happy to find that the drain tube was missing, it cured my primary leak, I no longer have a trail to follow to find my way home. LOL.
I have heard it said that some engine builders believe that leaving it out the rear main will drain quicker, agreed - except in the wrong direction - I think it was James Rogers explained why its there and how it works, if it is missing it is a low cost repair it may cure your problem.

[ModelAMadMan]

I drained the oil pan and re-filled with 3 quarts of fresh oil which now reads 1/2 way between "F" and "L" and the leak has decreased by about 2/3 or more. I do not know if the gasket between the flywheel and block was installed. Is there an easy way to check this? It looks as though the common answer here may be the drain tube. I'll look into that next. Thanks for all the replies.

[H. L. Chauvin]

Sounds something like this:

A. If oil level is "not" too high, &,

B. If oil fill breather cap allows air flow both ways as pistons move up & down,; &,

C. Oil leaking from the cotter pin hole is thinner lubrication oil as opposed to thicker transmission oil:

The next step is definitely:

Drop the oil pan & continue your investigation looking into all of items mentioned above.

[180 a]

look on the exhaust side of your engine, you should be able to see a little bit of the gasket protruding where the cam meets the flywheel housing. If you don't see a little bit of gasket it may be missing.

[rocket1]

Who is the rebuilder? I recently wrote a post on my rebuilder,we have to keep the Barners informed about these guys.I would drop the pan to check the drain tube and rear main,good luck,I found a short homemade tube causing my leak.