Oil leak


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By Jim Rowe - 18 Years Ago
Guys,



When I put my 312 together I used a neoprene rear main seal. The engine leaked from the beginning.



It only leaks until the engine gets one quart low on oil. ????? With 4 qts in the pan it doesn't leak at all. What gives.... Could this be a pan gasket and not a rear main leak?



Also when it has 5 qts in the pan she leaks from the draft tube. I have another dip stick and it also reads full with 5 qts in the motor.



No I'm not smoking any rope seal.



Got any ideas?



Jim
By Daniel Jessup - 18 Years Ago
Jim,

If your 312 has the side draft tube (on the side of the block, just aft of the fuel pump location). Of course, I cannot remember if any 312's have the side draft tube, I assume that all of them had the rear vent off the valley pan, but I digress.

Anyway, if you have the side draft tube, something I have noticed that happens on occasion - the can does not seal properly like it should (you didn't say whether or not the oil is coming out of the actual tube or leaking down the side, so understand that this could be a shot in the dark) that old can has a tendency to be just a tick smaller in diameter than the diameter of the tube/bracketry attached to the block. The seal sits in there nice, but the can is very, very easy to get a little cocked without even realizing that it is. Could be your trouble, hope this will help.

Dan

By Jim Rowe - 18 Years Ago
Dan,



Yes I have the side draft tube. It does have a leak as well. I have tried to silicone it and it still leaks.

This leak also stops when the engine is 1 qt. low on oil??



Thanks



Jim
By Daniel Jessup - 18 Years Ago
Jim,

Does the leak come from the inside or outside of the downdraft tube (or can you tell). As you know, a clogged filter can cause a leak, a clogged downspout can cause a leak, etc. The quart low on oil and the leak stopping? Your guess is as good as mine on that one. Do you know your actual psi on the oil pressure?

Dan

By Pete 55Tbird - 18 Years Ago
Hi; Just a thought. If your leak was at the rear main seal then why would it STOP when the oil quanity fell to 4 quarts? Get some of that dye that shows up under ultra violet light and a lite and check for the source of your leak. Or run the engine with 4 quarts of oil like millions of your fellow motorists do everyday. Pete
By PWH42 - 18 Years Ago
Along these same lines,what is the capacity of the pan on a 55 272?If I put 6 quarts in mine,as I do with my 56,it shows a quart over full,and leaks,which it doesn't do if run a quart low.Does a 55 272 only have a 5 quart capacity?