Rear Main Cap - leaking oil - please help

[garry viohl]

428 FE
Mains have been aligned bored
So the rear main cap sits lower than the oil pan rail
I think its leaking here
I have aviaid oil pan, windage tray and two Milodon oil pan composite gaskets

Oil leaking down the center of the block plate shield, sides clean
Flywheel clean
Rear main cap side rails sealed with black silicone
Rear seal is 6000 miles old
I checked it once before, looked good, I dont think its leaking

Any suggestions? An extra thin gasket to make flush with the rail? Maybe I should use the rubber and cork gaskets?
Thanks.

[RICK LAKE]

garry viohl Garry the rear main seal may be the problem. Is it a rope seal or Poly seal? The other problem is using RTV. I have not used Black sealer in about 10 years because of the black sealer leaks oil in low pressure areas. The heat cycles turn it hard. There is no elestic left in it, and it starts to weep and then seap. You end up with snail trials over time. I only now use the gray RTV. This is the same stuff the Honda used in the 80's and today. Unless the motor has 100 K miles on it, oil leaks are a thing of the past.
If you don't think the rear seal is leaken, buy a tube of the gray stuff at a GM dealership. Clean the area real good, install the part and give 24 hours to cure You can't have any oil dripping on this or the mounting surfaces. The other thing is to buy a leak check kit with dye for the motor. Put the dye in the motor, go for a 10-15 mile road test. Put the car up and look for a nice bright oil stain coming down from the motor. This will also save alot of guessing where the leak is coming from. I have seen rear leaks coming from the front of the motor out of the timing cover and the oil travels along the oil pan rail and leaks out the back. Rick L.

[Argess]

I think they only line hone, not bore, so the difference should be easily taken up with the existing gasket.

As above, the rear cap is hard to seal. You need a bit of RTV not only only the chamfered edge of the cap, but also a bit from the chamfer, along the block mating surface, to the seal. Seals shold be put in with one side about 1/4" up, and hte other end 1/4" down. Don't use RTV on the seal ends as it is too easy to get into the seal lip and cause trouble.

Then there's those darn nails. Near the end of driving them in, they sometimes compress the rubber side seal a bit. Gotta fill it up with RTV and let it cure before putting on the oil pan.

Oil Pan. I always use gasket shellac (stuff like molasses) on both sides of oil pan gaskets.

All that said and done, you can have an oil leak in the front where the oil is driven back and winds up along the face of the bellhousing cover plate by air motion as you drive. Front oil leaks can be from the front seal, dipstick tube and oil pressure sending unit fitting.

Improper crankcase venting can easily cause oil to burble up around the distributor, drain down and be swept back to the rear of the engine by air-flow. This is especially common with some non-Ford distributors where the groove for the dist tapered seal is cut too deep.

I am meticulous when I put together engines, and all I can say is all the FEs I did, all leaked some oil somewhere, and all of it looked like it was coming from the rear seal area.

I just live with it now.....LOL.