REAR MAIN LEAK

[mbc1967]

Hi all. Just got my 351W running and thought I did everything right. WHAT? The rear seal is leaking. The oil pan has no oil on it so I know it is not from there. The oil is running down the engine side of the block plate. Drips just a little when it is running. Drips about the size of a half dollar when you stop the engine. If any of you guys have had this problem let me know where to start. Thanks, Mike.

 

[BB1966]

Make sure the PCV hose is hooked up and not sucked together.

 

[mbc1967]

Make sure the PCV hose is hooked up and not sucked together.

I am not running a pcv just a breather. Is that bad?

 

[BB1966]

All depends if the breather is doing its job,new engine could have a little more base pressure. The little spring could have popped off the inside of the seal.

 

[CraigMBA]

I am not running a pcv just a breather. Is that bad?

Yes. Two breathers (one in each valve cover) is okay but one is bad news.

 

[mbc1967]

Well I put a PCV valve on and a breather on other side and it's still leaking. What would you guys do? I am thinking pulling the engine and see whats going on. Thanks Mike

 

[65FBE2]

I have had the same problem on my 347! spoke with my engine builder and he said that once in a while the cast in grove for the rear main is so out of round that you need to place a .01 shim under the seal. This is on a two piece seal block. It worked for me

 

[TOM B]

all ford cranks have OPEN holes in the rear crankshaft where the flywheel bolt on, You MUST use a sealer on the threads or you Will have a leak

 

[dennis112]

all ford cranks have OPEN holes in the rear crankshaft where the flywheel bolt on, You MUST use a sealer on the threads or you Will have a leak

351w's have blind bolt holes that don't use a sealer.

I suggest checking the rear of the intake manifold and the valve covers. They often cause what appears to be a rear mains seal leak.

Other possible causes is a loose oil galley plug or the rear camshaft core plug.

 

[mbc1967]

I have had the same problem on my 347! spoke with my engine builder and he said that once in a while the cast in grove for the rear main is so out of round that you need to place a .01 shim under the seal. This is on a two piece seal block. It worked for me

Were did you get your shim? Just in case.

 

[HookandLadder]

rear of the intake or valve covers. Do this before you yank it apart. Try some engine dye to isolate the leak spot.

 

[dennis112]

rear of the intake or valve covers. Do this before you yank it apart. Try some engine dye to isolate the leak spot.

Who stock engine dye? Will Napa have it?

 

[Rusty67]

Ya, thats something I'd like to know as well.