Does anyone know the reason for the crucifix seals located to the L&R of the #5 Bearing Cap? The reason I ask is that I have a rear leak (can't see of course this area) on my 04' reman engine and am just curious to the crucifix seals equation in the problem. The Rear Main of course seals the Crank Journal but I don't see the reason the Crucifix seals are in place.

 

If Im not mistaken, they are there to help seal the bearing cap where it meets the block. FWIW mine on my 03 went south @ 80xxx. There is a newer type available that are easier to fit. Bad news: you may end up r/r the rear main seal, too.

 

They're there to help prevent oil leaks, kind of a stop-gap between the main. the bad news is the "new" style were used in production for 03-04. Hylomar is also used on the surface where the cap meets the block. The omission of this step or incorrect application could certainly contribute to leaks.

Leaks in the rear of the oil pan and/or gallery plugs can look like a main leak also and are often mis-diagnosed as such.

 

I used Permatex Ultra Black RTV on the Cap instead of the Hylomar. Do you think this is why I'm leaking?

 

I really can't give you a qualified definitive on that as I'm not a sealant expert but I really doubt it. I actually misspoke earlier, out of habit I said Hylomar but the current "correct" sealant is locktite 5900. Obviously there must be some differences between they and the regular Permatex but I would guess jobs completed with the "proper" RTV are the exception and not the rule. Like I said, I'm not a sealant expert but if I were diagnosing your leak I would eliminate absolutely everything else first. Again, deeply sorry for the product confusion.