Hello everyone, I am a long time reader but first time poster; I have a 1983 F100 with a 300c.i. Straight six & a c6 Automatic Transmission. I recently developed an oil leak. So I did the oil pan. I also did the common upgrade of shaving down the flanges around the bolt holes and moving to the newer style one piece molded rubber gasket. After going through the whole process and putting it back together I still have the same oil leak in the same place at the very back of the oil pan. I am unsure of whether I did it wrong and didn’t seat the seal properly at the back of the oil pan or if the rear main seal is actually the culprit. Any help would be appreciated. Thanks.

also here’s the link to the forum I used to do the gasket upgrade:

https://www.ford-trucks.com/forums/1...-oil-leak.html

 

The first thing you need to do is blast the underside of the engine clean and use dye penetrant to id your oil leak. It may be coming from your rear main seal. You can get kits at your local auto parts store. Here's one I found but haven't used.

 

I did put dye in the oil, and I also cleaned up the pan while I was under there. The oil leak is coming from the very back of the pan right where it curves down to clear the crankshaft. But it’s also running down the fly wheel cover, it’s happening in a way that makes it very difficult at least for my eyes to determine if it is the rear main seal or the oil pan, I can post pictures when I get homes tonight; Not sure if my camera will pick up the UV dye and light or not but we will see.

 

Oil leaks are hard to find sometimes. A valve cover gasket leak can run down the back of the engine. Also if you have a oil pressure sending unit or switch back there, they can leak and run down the back of the engine. On a v8 the rear of the intake manifold can leak and look like a rear main.