I think the rear main seal on my 57 312 is starting to leak more than just a few drips ans drops, when the engine is cold. Once the engine is up to operating temp, the leak seems to disappear. I havea few questions.

1) Do I have to yank the motor out of the car to fix this.

2) What is the best way to fix it. I only want to do this once, if possible.

3) Is this one of those repairs that require tearing down the bottom end of the motor, to do it right? My thinking is, if I have to go that deep into it, I may as well plan on arebuild.

Here's the catch. I have it from a very trusted source, that no matter what I do, the rear main seal on the 312 YBlock, has been and always will be, problematic.

What are your thoughts? If I have to pull the motor, I need to know that the fix will work. 80% - 90% success rate would be good.

Currently she runs pretty strong and does not burn any oil, but may be exibiting the occasional tell tale pops of the beginings of a burnt valve.

Your help and advice, is appreciated!



Bill Poland

312 V8 - in a 1957 T-Bird

Baltimore, Maryland

Bill: rear main seals are touchy to repair properly. With the right tools & method they can be done in chassis, but it's not easy. I'll mention that rear seals problems are worsened by the fact that most original seals contained asbestos, which is not readily available anymore. The replacements have often been less satisfactory than originals. However, Best Gaskets make two types of later seals for the 312s. One is a silicon rubber seal & the other is made from Teflon. You might want to order both to have on hand. If you do a search here, you will find info on doing the job right... As for pulling the engine, you say it may have a bad valve. You can pull the head (s) without removing the engine... Another thing that apparently can increase oil leakage is plugged up crankcase venting. Make sure the air intake thru the oil filler cap is clean & clear & the lower cankcase canister filter isn't plugged up. Some owner have lessened leakage by converting to a PCV setup. It gives a slight vacuum effect on the crank case, easing leakage. Good Luck.

Paul

The TBird does not have a canister crankcase vent. It is vented by a downdraft tube located in the rear of the valley pan.

54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

Many years ago, I had the experience of fixing y-block rear seals on two different engines. I say 'fixing' because in both cases the full rope seal was not replaced!

The engines were in vehicles. The oil pan was dropped (after disconnecting the oil pick-up tube to the oil pump), and the rear seal retainer was removed. The crank assembly (main bearing caps, etc.) was not disturbed in any way on either repair.

Two steel shims of equal length were tapped up into the cylinder block seal retainer groove between the rope seal and the retainer groove. These shims served as wedges to force the upper rope seal against the crank seal surface. The shims were made from spring steel strips, were approximately .060 thick, had a width of approximately 3/16 inch, and the ends that were tapped into the upper rope seal retainer were radiused so as to have somewhat of a bullet (cone) shape. Also, the lead edge of the radiused nose of the shim, the edge nearest the rope seal, was tapered and rounded so as to not catch on the rope as it was tapped into place. The steel shims were tapped until flush with the block mating surface for the removable lower seal retainer.

The lower rope seal was replaced in the removable aluminum seal retainer per standard repair manual procedure and reinstalled per the same repair manual. After cleaning the oil pan, servicing the oil pan bolt holes, replacing the pan gasket, and reinstalling the oil pan and reconnecting the oil pump pick-up tube you'll be done except for adding engine oil.

In both cases, rear seal leakage was stopped. The rear seal repair was successful.

I'm told that farm equipment suppliers had this type of rope seal replacement 'kit' available for use on farm tractors at least back in the '60s.

Hope this helps.

NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Ah Yes, Blame the rear main. One problem that always gets blamed on the rear main is actually the seal on the adapter plate to the block for the spin on oil filter. The original was thick paper and required a thin coat of oil or grease when installed and the replacement is neopreme and should be put on dry or will leak slightly and flow down to the back and appear as a rear main leak. The 312 was improved over the other 'Y's and did not have the oil leak as the early ones did.

312T85Bird

What?

When I got my 57 bird seven years ago, it had a major rear main leaking. My mechanic tried a new rope seal and it was no better. He then tried a GENERIC neoprene seal-no better. I then purchased a kit from PRESTIGE THUNDERBIRD in California. It has stopped the leak. It was done with the engine in the car. Drop the pan, loosen crankshaft end caps and install.

Hope that helps.