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Post Info TOPIC: What do I do? Trying to fix oil leak
jim larson


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What do I do? Trying to fix oil leak
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When I Dyno the engine last week, there was a small leak, about 5 drops of oil that appeared just below the area where the bottom of the timing cover and the bottom of the oil pan. I think it came from a slow leak coming from the oil pan.  Aftermarket oil pan and 76 truck block which I think calls for the thick front seal, which Derek recalls using.

Is there a quick fix or must I put in a new gasket set?



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Jim L

Lake City
Larry Lucast


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Probably you can loosen the pan and squeeze a little silicon into the corners.

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Larry L.

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jim larson


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I think I have determined where the leak is common from.  Is there an additive I can dump in the oil, so I can clean everything and the verify for sure.  I think the oil pan is good.  Looks like the leak is coming from the timing cover crankshaft seal. New balancer, gm original 69 timing cover,  original 76 gm crankshaft ground 10/10 on the current rebuild.  New seal for timing cover.  Looks like oil runs down from timing cover seal area down the timing cover to the lip at the bottom then around that lip to the bottom area where everything meets and the drips to the floor.  Which the oil was dirtier and easier to see.

Also, if I remove the timing cover, how can I do that with out damage to the oil pan seal? I don’t want to disturb the oil pan gaskets.



-- Edited by jim larson on Thursday 3rd of June 2021 02:01:22 PM

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Jim L

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The front pan seal is embedded in a channel of the timing cover and will come out with the cover. Impossible to NOT disturb it. The cover has to be pulled very far forward at the top and pried out of the pan due to the channel sitting behind the pan. It's a big PITA to get it back together and it will leak at the cover corners when done.

Since everything is new where the seal leaks now, I'd bet the oil is migrating past the seal frame. Some have a sealant on the outside of the metal, but I always use a small amount of the Ultra Black sealant, we talked about at Karl's, on the exterior before pressing the seal into the cover.


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Mitch D.   River Falls, WI

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1966 Chevelle SS 396 M20

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Larry Lucast


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Good catch on your part to find the leak. I agree with Mitch about the seal frame. If you loosen pan bolts at the back, and remove some closer to the front, You might be able to push the pan down enough to pull the cover almost straight out. Use a little silicone when you put it back together.

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Larry L.

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jim larson


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Still investigating where the leak is coming from, now to clean, clean. Then taping some cotton balls  up along the timing cover to see if oil is coming from balancer/ crankshaft seal in the timing cover.  Checking again this morning and back to Mitches thought.  I put about a quart of automatic trans fluid in after 4 qt if oil.  Hope to find for SURE where the leak is at. Leaking very little now, maybe the ATF is acting like a sealant. 



-- Edited by jim larson on Friday 4th of June 2021 10:26:21 AM

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Jim L

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