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post #1 of (permalink) Old 05-31-2009, 05:14 PM Thread Starter
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Leaking oil between engine and bell housing

Folks,

Ever since I've owned my '81 CJ7 it has ALWAYS leaked oil while the engine is running between what seems like the engine and the bell housing. It's along this seam between the two which seems to show the oil after I've wiped everything clean.

My '81 has a 258 and a T-5 transmission.

Any thoughts on what could be the source of the leak and how hard it would be to repair?

Thanks!

-John
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post #2 of (permalink) Old 05-31-2009, 06:35 PM
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It could be the rear main seal or it could be the valve cover, or both. If the top of the engine is oily between the valve cover and firewall, then the valve cover might be the problem. If the top of the engine is dry, then my bet would be on the rear main seal.

How much oil are we talking, a few drops or a couple of quarts? Did you ever replace the stock plastic cover?

-- mike
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post #3 of (permalink) Old 05-31-2009, 07:07 PM Thread Starter
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Engine seems to be pretty clean of oil. In terms of oil lost - I would say it's a 1/2 quart every few weeks of driving.

So - I'm going to show my ignorance - what plastic cover are you speaking of?

-John
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post #4 of (permalink) Old 05-31-2009, 07:26 PM
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Some of the Jeeps had a plastic valve cover on top of the engine...
It's not actually a 'Valve' cover, it's the cover at the very top of the engine that keeps crud out of the rockers.

Check the sides/back of your block, If you DO NOT see a bunch of oil on them,
Then it's the Rear Crankshaft Main Seal.

There is a big seal at both ends of the crank shaft, Front & Rear.
The REAR MAIN SEAL is prone to leaking in the CJ engines, especially when you have a manual transmission with a heavy clutch and flywheel hanging on the very end of that crankshaft.

Changing rear mains IS NOT something for beginners, better left to the professionals...
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post #5 of (permalink) Old 05-31-2009, 07:26 PM
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Plastic valve cover. They're notorious for leaking. I guess they're a little too flexible to clamp down hard enough on the gasket.

EVERYTHING's easy for the guy who doesn't have to do it.
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post #6 of (permalink) Old 05-31-2009, 10:28 PM
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Quote:
Originally Posted by Jim_Lou View Post
Plastic valve cover. They're notorious for leaking. I guess they're a little too flexible to clamp down hard enough on the gasket.
They just warp with heat/time and arch up between bolts.

Also, you can't get anyone to use an inch pound torque wrench on anything, so the bolts are ALWAYS overtightened, and that causes 'Arches' between bolts....
That leak like CRAZY!

The torque spec for the plastic rocker covers is like 25 or 30 INCH pounds, and I have seen the bolts twisted off more than once where some guy got "Gorilla Grip" going on the bolts!

The tell of the tape usually is,...
Do you have oil INSIDE the bell housing.
If so, it's the rear main seal 99.99% of the time.
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post #7 of (permalink) Old 05-31-2009, 10:41 PM
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Hmm, I have a couple of 258's with those nasty plastic valve covers. They don't leak.

If it's not leaking on top... Then it's leaking around the crank.

Yes as already posted... But don't trash the trashy plastic junk. It can work too.


Dale

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post #8 of (permalink) Old 06-01-2009, 12:35 AM
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I had a good method getting the plastic cover to seal....

Take it off and clean everything real good.
Run a large bead of RTV (about 1/4") around the surface of the valve cover.
Let it sit long enough to not be tacky...about 1 hr
Then carefully set it in place....but don't tighten it....just gently snug the bolts.
Let it sit over night....then tighten the bolts.

Never had a leak with that method.

But my vote is on the rear seal.....and actually...it's not that hard....

In relative terms....if doing your own brakes is beyond your skills....let someone else do it....

But if you do your own brakes...then the rear seal is not that hard.
Drop the pan (you will have to jack up one side of the engine to clear the motor mount)
Remove the rear cap on the crank.
With a punch, 'carefully' tap on one side of the seal...it should rotate right out.
Slide a new one in...using plenty of oil.
Replace the one on the cap.
Re-torque the main cap.
Put the pan back on.

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post #9 of (permalink) Old 06-01-2009, 01:10 AM
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One thing to add to JeepDawg's instructions for the rear main seal. There are a couple of places the manuals show to apply RTV or other sealer to the rear main cap, see attached. I do not know if the RTV is needed but I have always done them as the manuals show and they did not leak.
Attached Images
File Type: jpg rear main.JPG (23.1 KB, 10 views)

Wilhelm

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