Rear main leak?

[jeepfunatic]

I finished building my stroker 258 12 counterweight crank, bored .030 over, 258 rods. Block#53008405. About 500 miles after my rebuild I'm almost positive after looking hard into where the oil is coming from it looks to be leaking from the rear main. Is it possible that I put the wrong seal in or can it be installed backwards? The gasket kit that I got was for 87-91 4.0l/242 engines. I changed the oil 2 weeks ago and it already leaked out a quart, thats how bad it is.

[SilverXJ]

Did you use and RTV when you assembled it?

[dwg86]

What year block? Sometime around 2000 or 2001 the rear main seal was changed. The older style had a funny looking seal that went into the rear cap. On this type of seal I like to use a small dab of RTV on the ends of the seal where they mate together. If it's the newer type seal (half circle in the block and cap), offset the seal about 3/8 of an inch, so the split in the seal doesn't match up with the split of the main cap. On both style seals, the rear main cap has a small chamfer on the left and right side of the cap where it mates to the bock. This needs to be sealed with RTV or it will leak. I clean the block and cap in this area with brake cleaner and use a toothpick to put a small bead of RTV to seal the ends of the cap.

Oh yeah,in the older style seal, you can put the block side seal in backwards. On the newer style seal, both sides can be installed backwards.

[John]

And what oil pressures have you seen since the rebuild.... Excessive oil pressure can be hard on this seal.
John

[amcinstaller]

dwg beat me to it. make sure the lip points towards the oil. also, when i did mine in my jeep, i pinched the oil pan gasket the first time, looked the same as a rms leak. and rtv never hurts

[jeepfunatic]

I only put RTV on the to little lips. Oil pressure is between 50-60psi. The psi is lower now that I changed out the racing oil used for break in. When I get it out today I will pay close attention to see if I installed it backwards.

[dwg86]

Don't forget to seal the chamfer on the main cap.

[jeepfunatic]

Don't forget to seal the chamfer on the main cap.

Thanx