Blankety-Blank Rear Seal!!!!

Yup the rear of the valve cover.

The rear of the head below the valve cover is as dry as a bone all the way across, and ther's no sign of a leak anywhere else around the cover. ?????

I would say the oil gallery plug is more than likely the culprit.

Chris

Jerry, I had to try three times to stop that "rear main seal" leak on my 88. First the rear main - helped a lot but still had a drip. Next, I noticed that when I put my hand up behind the oil filter I got a little oil on it. Darned oil filter adapter was leaking, running back along a casting rige and dripping! Not a trace of oil coming down, it was all running back and dripping down the shield (the 88 has a tine shield all the way up behind the flywheel). OK, that slowed it some more. After that, I decided to look really close and sure enough, the front seal was leaking a little and pulling the same trick

- blowing back and running down just like a rear main. Once I wised up, I could find those blowback traces with a rag but they sure weren't obvious. I haven't seen another case like that but it's worth a few minutes to look. Any chance that the crank has a rough spot under the rear main seal?

you want to get one of those aluminium ones which run noticeably quieter and don't leak :-)

Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ

Thanks, Will. I'll check it over again today. I let it sit overnight for the sealers to cure, but I have no faith it's been fixed this time any more than it was before. The "old" seal came out looking like new, so I don't think the sealing area's scratched up. The valve cover's sealed as tight as a drum and the filter area and front seal are dry as a bone. Only other thing I can think to do is to pull the trans and the separator plate to sdee if the galley plug is leaking. (If I do that I GUARANTEE that won't be it!)

The valve cover does a really good imitation of a rear main seal leak. I did the same as you, replaced the seal and pan gasket twice, and on the test drive after the second go around, I parked on a hill and could literally see the oil flowing out of the valve cover. The cork gasket is about a quarter inch thick, and when it cracks, the two pieces draw apart from one another, and create a HUGE HOLE that the oil flows through. The oil runs down the back of the block, through the bell housing and out the bottom of the clutch inspection plate. It looks for all the world like the rear main is leaking, but the oil has travelled all of the way down the block before dripping off the bottom of the bellhousing.

I know, I shot it down as well. I was wrong.

Someone here bought an ally one and it leaked like crazy !

I remember that, it was a Clifford that was warped or something.

The tightening sequence for covers with holes around the outside is to start in the center and work in a circle towards the ends. But, if the cover is warped, this will almost guarantee that it leaks. The better approach would be to tighten the cover at the rear of the motor first, then work back and forth towards the front. This way, if there is a warp, it produces a gap at the high end of the motor, not the low end.

When installing the valve cover, one should place it on a flat surface and see it it can be rocked from end to end. Press one end down, and see if the other end rises off of the surface. If so, then it would be best to get a new cover, or tighten it down by starting at the rear of the motor so the poor seal is at the highest point on the motor instead of the lowest.

It'll come back, no matter how many times you change it. It may be a day, a week, or a month max, but it will come back. Just think of it as preservative for the bottom of your tub and drive train.

week, or a month max, but it will come back. Just think of it as preservative for the bottom of your tub and drive train.>

I know, since it was new it's been replaced at least 5 times in 65k miles. We'll see how long this one goes.