Leak that healed itself...
 

About 500 miles ago, I replaced the well worn original engine in my 30 Tudor with a good used engine. The original engine didn't leak a drop.

The "new" engine was .080 over and the pistons seemed tight in the bores. I replaced 2 valves and lapped them all in and set clearances. The babbitt looked near new except for #1 rod which had started coming apart. I replaced it with a newly re-babbitted one from Bert's. The rod journals were .020 under. I didn't measure the mains. The mains all looked great and plastigaged at .0015 clearance.

It leaked from the rear of the engine for the last 400 miles. I removed the half moon shaped cover from the flywheel housing, dried everything off and observed this area with the engine running. The oil seemed to drip off the very rear of the rear main and run forward along the bottom of the main cap then drop off and "probably" ran under the half moon shaped cover. No oil ever came out of the bottom of the flywheel housing where the big cotter pin is.

Within the last 100 miles the leak stopped. I think I'm happy but don't understand how this could happen. I guess there is a chance that the rear main is no longer getting any oil, but I try not to think about that.

Any other explanations?

Re: Leak that healed itself...
 

It stopped leaking when there was no oil left!:D

Re: Leak that healed itself...
 

I know Synchro99 is joking about being out of oil but he could be 1/2 right and level has dropped to where the car is happy. Take note of the level on the dipstick and only fill to that level from now on.

Re: Leak that healed itself...
 

Thanks, Mike.

I put in 5 quarts after I put the engine back together and installed it (1 qt through the dizzy hole into the valve chamber). After warm up, the oil level was right at the bottom of the F on the dip stick. 500 miles later, still right at the bottom of the F. I don't think that's it, but thanks for the idea.

Re: Leak that healed itself...
 

Thank you, Thank you Mike V. Florida. I posted a couple of years ago that I was running my old engine near to the low mark on the dipstick with no leaks. Above this level it was making a real mess! I was lambasted for this - 'Henry put the F mark for good reason' etc..... Now my new engine is doing exactly the same - and the dipsticks are identical!
- GOOD ADVICE Mike - thank you

Re: Leak that healed itself...
 

I have had leaks get better, than worse, than better again over the years we have owned our 29. “40 years”. Oil drip has been at rear of engine.

We have had the pan off twice and checked everything. Never found cause, if there is one.

I always tell people that “Model A’s mark their spots”.

My personal view on running engines down one quart is not to do it. With the already marginal cooling system, I think the engine needs any additional cooling help the oil brings.

What weight engine oil are you running? Enjoy.

Re: Leak that healed itself...
 

Maybe the rings broke in and now you have less crankcase pressure.

Re: Leak that healed itself...
 

...and breather tube is plugged.

Re: Leak that healed itself...
 

:confused::confused::confused:

Re: Leak that healed itself...
 

Don't mean to overstate the obvious, but are you inserting both ends of the dipstick in the hole?

Re: Leak that healed itself...
 

There are lots of threads about Model A's being sensitive to oil fill level with regards to leaks. There are lots of threads about different length dipsticks. Yours sounds OK based on the 5qt in an empty engine scenario.

There are 2 marks on a dipstick for a reason. It means the oil should be between the 2 marks. If you can keep your oil low, but still between the 2 marks, and it helps the leak, then go for it. It may mean you check your oil a lot. So what.

Also, the Janitor, a little cup they sell for the main drip, works pretty well. I put a bit of rag in mine to stop sloshing.