3 Leaks down, Need help with #4

[1987Comanche]

I've been working on the '90 as much as time allows (it goes to work 5X/week) and I've managed to fix 3 of my 4 fluid leaks (radiator, clutch master cylinder, gas tank). The 4th one, for some reason, has decided to be stubborn. My Renix 4.0 was leaking oil profusely when I got her and I had to drop the pan to clean the carbon out of it. While I was there she got a high vol oil pump, new rear main, and new oil pan gasket. The amount of oil leaking remained roughly the same.

Fast forward 2 months...I've finally given up on my attempts to make the CCV system function properly and routed the front hose (on a '96 valve cover) to a catch can. When I purchased my '87 2.5MJ she bled oil profusely and 90% of the problem turned out to be the PCV system (motor was out of an '86).

Here's the question: Is it worth going back in to do the rear main & oil pan gasket again? When I park I end up with at least a 5" X 7" size puddle of oil that looks like it's coming from the rear main. If the CCV system is at fault and the 4.0 behaves like the 2.5 then it will be a wasted effort because the crank case pressure is too high. For reference I loose about 1/2 quart between fill ups (200-225 miles).

[maddzz1]

Did you put the 96 valve cover on or was it on there when you got the truck? Did you get rid of the unneeded vacuum lines when the switch was done? (mjeff87 has a write up on this somewhere) Did you use the cork VC gasket or get the good felpro one? Did you use the VC gasket for the 96 (black if felpro) or the one from the 90 (blue if felpro)? you need to use the newer one. I also thought my rear main was leaking, but it turned out the back of my valve cover was leaking oil down the back of the engine and dripping down past the rear main.

[Pete M]

I dropped the oil pan 5 times before I successfully got the RMS to stop leaking. :(

 

but I'd do the east stuff first and check for oil leaking at the back of the valve cover. they are notorious for leaking back there and looking like a RMS.

[87mjdriver]

I ssecond the valve cover, check it

 

I retighten mine every month or so.

[1987Comanche]

I added the '96 VC in an attempt to get the CCV system sorted out. I used the black Felpro gasket and the gasket & JY VC together cost the same as the blue Felpro gasket for the cast AL VC. I didn't have any extra vacuum lines..just changed the fitting on the intake to accomodate the new CCV line and spliced the plastic tubing to hook it up to the air cleaner. I'll check the back of the valve cover but, unfortunately I'm pretty sure it's the RMS again,

I did have to hook the vent line back up to the air cleaner. It jacked the crankcase pressure up and she dumped nearly 1QT oil in 80 miles. interestingly enough the oil pressure gauge read 10PSI higher than normal during this time period. Instead of the normal puddle under the truck I had a slick! I suppose the air filter will be permanently oil soaked.

Pete: What did you do differently on the 5th try that made it work?

[Pete M]

each try was a for different reasons. It's been a while (and my memory sucks) but among the problems were a nicked seal, not enough silicone in all the right places, and not waiting 'til the silicone cured. But it's not like I knew for sure each time. :dunno: I just knew that it was still leaking. :(

[1987Comanche]

I think the most likely culprit is a nicked seal. The OE RMS was incredibly difficult to remove and the replacement required some tapping to get into place. I'd guess that, if I have to do it again, it will come out a lot easier. Also the OE seal was extremely brittle when it came out. Did you find them easier to remove after the OE one came out?

[Pete M]

I put a bit of grease in there before installing the new seal

[88 Beast]

Did my rear main awhile back, seal must have been original. Hard as a rock and came out in pieces. No leaks for about a month. I should have known because of the groove worn in the crank from that old seal it wasn't going to last :mad: Guess when I get motivated I'll do it AGAIN with the double lip seal and one piece pan gasket.

[1987Comanche]

Double lip seal??? You peaked my interest. Do you have a Part # and supplier? I'd like to only do this one more time...

[88 Beast]

Don't know the part numbers, but heard about them here. Maybe someone in the know will pipe in. I could use the part #'s too.

[manche75]

Is the seal you put in a 2 piece main seal?

[88 Beast]

Yup, got it at NAPA

[manche75]

Did you stagger it when you put it in?

[maddzz1]

I have one of the 2 piece double lip seals at home. I will check the part # and post it tomorrow. I think I ordered it thru rockauto

 

EDIT: Found it on rockauto. Part# Felpro BS40612

[88 Beast]

Thanks, how bout the pan gasket #?

[maddzz1]

Thanks, how bout the pan gasket #?

 

The one piece gasket for the AW4 (automatic) is:

 

Felpro part# :TOS18685