Rear main seal - JeepForum.com
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post #1 of 8 Old 04-04-2020, 02:53 PM Thread Starter
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Rear main seal

So I am new to posting so forgive in any norms I break. I have a 1983 CJ7 with the inline six. It has a leaking rear main. The engine has good compression. I was told that I can replace the rear main seal inframe. I have done some research and seen this to be true. My question in this forum, is has anyone done this? And can you forward in hints, tricks or things to watch out for. I am handicap and will be doing this my self in my driveway. Not a big idea, just takes a couple hours longer is all. Thank you for any ideas you may have.
CE retired LEO,Commander, WSPD, Fish and Game div.

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post #2 of 8 Old 04-04-2020, 04:03 PM
Axhammer
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Iím not sure about changing a rear main seal, but I know the valve cover can leak at the rear, and look like a rear main seal leak, when it isnít. I had a leaking valve cover that I fixed by replacing the gasket. Then a few weeks later my engine started leaking again, and it was dripping down the back of the engine and off the front of the transmission. It looked like a rear mail seal leak. I cleaned up underneath and the back of the engine, all the way up to the valve cover and then drove it some more, and I discovered it looked like it was the valve cover leaking again. When I removed the valve cover I found the rear most stud had broken. I put it back together with a new gasket & stud, and it hasnít leaked since.

I suggest you verify itís not the back of your valve cover leaking down the back of your engine.
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post #3 of 8 Old 04-04-2020, 04:30 PM
gojeepgo
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Its not a terribly difficult job. If I remember correctly the engine needs to be jacked up and one of the motor mounts removed so you can drop the oil pan. The seal is a two piece part. When sliding the new half into the block be sure to have it oiled up well. If you accidentally shave any of the rubber off the seal on install its junk and you'll need another new one. The other half goes in the rear bearing cap for the crank. Make sure the bearing cap goes back on in the same orientation it came out and torque the bolts down to spec.
You'll also need a new oil pan gasket.
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post #4 of 8 Old 04-04-2020, 05:56 PM
Axhammer
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Go to post #22 of this thread for a tool to support the motor, while the motor mount is removed. This is required to remove the oil pan, while engine is installed.

https://www.jeepforum.com/forum/f8/j...05/index2.html

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post #5 of 8 Old 04-04-2020, 07:30 PM
87MJTim
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Parts needed:
FelPro blue rubber reusable one piece gasket set. (If you ever perform this process again, you will thank me.)
Re-main seal.
6 quarts oil
oil filter.



It's a messy job.
Raise the front end, let the front axle hang down. You do not have to remove the tires.
It's a messy job.
Disconnect battery. Remove the starter.
It's a messy job.
Place a floor jack at the trans bell housing. Loosen the passenger side engine mount. Slowly raise the jack to lift engine off mounting bracket.
It's a messy job.
Remove all the bolts around the oil pan. You may need some gentle persuasion to loosen/remove the pan. Be careful lowering the pan from the engine because of the oil pickup tube.
It's a messy job.
Remove the rear main bearing cap.
It's a messy job.
Half of the seal in inserted on the bearing cap. Remove old; install new.
It's a messy job.
Using a brass punch, CAREFULLY push out the top seal between the crank and engine block. DO NOT scar the crank.
It's a messy job.
Coat the new seal with oil or liquid dish soap to insert in the engine. Make sure it is facing the proper direction! The punch can help get it flush with the surface.
It's a messy job.
Put a little RTV on the edges of the two halves of the seal before re-installing the bearing cap. Torque to factory spec.
It's a messy job.
Reverse your steps to install the oil pan, re-seat the engine mount, attached starter, attach battery cable.

I may have missed something.
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87 Comanche, 4.0, AX15 (formerly BA10/5), D44
84 CJ7, 4.0 (93 XJ) AX15 (Formerly T5)
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post #6 of 8 Old 04-05-2020, 07:10 AM
Matt1981CJ7
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Don't forget to use RTV sealant at the places indicated in this diagram.

Matt
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post #7 of 8 Old 04-05-2020, 07:42 AM
bob4703
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Please before you proceed with replacing the RMS verify it isn't the valve cover leaking. As AX said a leaking valve cover can give you a false positive on a leaking RMS. You haven't said how long you have owned your Jeep or if you have changed the valve cover gasket. If you don't know change it before going further. The single bolt in the rear of the valve cover is a PIA to get to. Some folks don't get it tight and often forget to retorque the bolts after a few days. Buy a can of Gunk and use the spray washer or take it to the car wash and ensure it is clean. If a new gasket doesn't solve your problem you have prevented the next leak.

A close gearhead friend once said "I wish I had a done that first!" Good luck!

-----

Paved roads are prime examples of government over spending!

Last edited by bob4703; 04-05-2020 at 07:45 AM. Reason: Added the missing "a" from the quote.
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post #8 of 8 Old 04-06-2020, 04:41 PM Thread Starter
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Thank you all for the advice. I had eliminated the valve cover early on. I should have posted that. I completed the seal change out today using all Felpro blue and seal set. Took two days and lots of pre planning as once I was under the jeep getting out and up was my challenge. After a 20 mile ride I have no leaks. I steam cleaned everything so the next 1000 miles and our Central Oregon temps should tell me everything. Again Thank you all for the great advice.
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