Rear main seal? -
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Unread 05-03-2002, 02:19 PM   #1
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Join Date: May 2002
Location: Marstons Mills, MA
Posts: 125
Rear main seal?

Hello. I'm new to the jeep community. Although I have always wanted a jeep, I just now have the means to make it happen. Anyway my question is: How do I know if my rear main seal is bad? There is a lot of oil around the back of the motor and the bell housing. I've been told that it could be the rear main seal, but what do I know. If this is a possiblity what kind of $ am I looking at to fix the problem. Any input is appreciated.

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Unread 05-03-2002, 09:36 PM   #2
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Join Date: Mar 2002
Posts: 17
OK, I just did my engine (major OH) for my 81 CJ and can answer this one from experience.

First you must look for the source of the oil. Normally a rear main is just as you described. Oil on pan, rear of engine, clutch, bell housing, and often all the way back to the drive shafts. Lots of oil. Oil coming out as it sits and moves is what happens if the rear main is hopelessly cracked. Just a single drip, Hmmm probably means starting to go, the more the worse it is. But not necessarily.

My CJ had a huge leak or I should say the previous owner had a huge leak that he was convinced was the rear main and that is part of the reason it was here. The rear main was not the problem, however, it was a bolt problem at the back of the oil pan. Moral of the story: look for cheap dumb things someone has done to the poor thing. This one was pulling the pan and not putting in the right bolts in the right holes. They used the same fasteners at the front and rear corner which are actually 5/16 bolts and the rest are 1/4" it leaked like a storm!

Anyway, putting in a rear main is fairly straight forward. Remove pan, remove the rear bearing cap. Take out the seal in the cap and change it. Hook the other one out and drag it out. May take pliers, screwdrivers and cutting. Clean up the seal groove VERY WELL. Put the new one in. Everyone has their way, probably string and grease is a way, or wire. Pull the one end thru without trashing it! Make sure it is pretty even! Put the bearing cap back and torque, put the pan back and torque it. Probably 200+ at a good shop. Get a guarantee about leakage! Hope this helps. If you have any more Qs about the 258 engine at all I can answer most with very fresh memory!
1981 cj looking to do fun stuff with the cj and my kids.
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Unread 05-04-2002, 06:34 AM   #3
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Join Date: Mar 2002
Location: Southern Rhode Island
Posts: 1,527
What he said!

Also, keep in mind, the rear of the valve covers on 258s leak fairly often, and they can leak a considerable amount, also contributing to the wetness in the same areas. A Cast-Aluminum Cover with cork gasket is your best bet for a "permanent" fix. I put it in quotes because NOTHING on a Jeep is permanent, but you know what I mean, LOL. <img border="0" title="" alt="[Wink]" src="wink.gif" />
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Unread 05-04-2002, 02:35 PM   #4
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Join Date: Jul 2001
Posts: 53
Dont forget to put the lip of the seal inward. <img border="0" title="" alt="[Wink]" src="wink.gif" />
'78 CJ7
360 cid W/390 heads
edelbrock intake W/matched performer plus cam,springs and timing chain
Hedman Fenderwell headers
4WD Fiberglass Body
4" lift W/ 35" BF Goodrich AT
Pioneer CD player W/ Pioneer 200 watt amp – 10 in. sub speaker box Shoved behind rear seat for now (Till I can make a permanent box)
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