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Replacing the Rear Main Seal |
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fullgarage 
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Joined: 15 May 2020 Location: Celina, TX Status: Offline Points: 41 |
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 Topic: Replacing the Rear Main SealPosted: 27 Feb. 2021 at 10:29pm |
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I have put two neoprene rear seals in my CJ and it still leaks. The first one came in the Fel-Pro gasket set and the second one was the "Best" seal that many on the board have had great success with. Today I tried to install a rope seal with the engine in the jeep and it was a total fail. We could not get the seal pulled around despite following the advice of many.
I intend to get another rope seal kit and am trying to decide which is better, pull the engine, or pull the transmission? I have had the transmission out before and I know I can pull it in an hour or so. I have a lift, which makes removing the transfer case and transmission pretty easy. if I pull the transmission, remove the clutch and flywheel, I assume I can lower the crank by removing the main caps and get enough room to change the seal. Am I missing something? Removing the engine seems to require more disassembly and requires an engine hoist which I don't have. I could rent one I am sure, but is the engine route harder or easier?
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David - Celina,TX
1948 CJ-2a (on the road but never finished) |
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Joe DeYoung
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Posted: 01 Mar. 2021 at 3:32am |
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A rope seal needs to be properly 'kneeded' into the block and cap to be successful. I highly recommend taking the engine out and removing the crank to do this.
As a side note for others... The newer rubber lip seals requires the crank shaft to have a main seal diameter of 2.345
Edited by Joe DeYoung - 01 Mar. 2021 at 2:36pm |
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Joe DeYoung
to many jeeps, parts, and accessories to list here, but apparently enough to keep me in trouble with my wife. |
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Mark W.
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Posted: 01 Mar. 2021 at 6:57am |
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The seal surface must be smooth for any seal to work properly
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Chug A Lug
1948 2A Body Customized 1949 3A W/S 1957 CJ5 Frame Modified Late 50's 134L 9.25"clutch T90A D18 (1.25") D44/30 flanged E-Locker D25 5.38 Since 1962 |
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uncamoney
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Joined: 26 June 2019 Location: greeley co Status: Offline Points: 451 |
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Posted: 01 Mar. 2021 at 8:12am |
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I rebuilt my MB motor, it would outrun a F134. . i couldn't keep oil in it despite 4 attemps to fix the rear oil seal, rope or neoprene. As far as I knew the crank grinder took the surface down too much.
I fixed it by dropping in a Fireball V6. Change the entire drive train. One of the fastest Jeeps I have ever driven. The other had a built Corvette 327 race motor, there are limits....
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john
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Oldpappy
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Posted: 01 Mar. 2021 at 11:54am |
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"I fixed it by dropping in a Fireball V6. Change the entire drive train."
Now that is some "fix"!
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If you can't get there in a Jeep you don't need to be there!
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Oilleaker1
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Joined: 06 Sep. 2011 Location: Black Hills, SD Status: Offline Points: 4412 |
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Posted: 01 Mar. 2021 at 12:00pm |
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Metal Shaper videos on you tube has both rope and neoprene rear main seal informative videos on this topic. I highly recommend you look them up.
As Joe mentioned there are correct size and condition of the crank shaft journal that work with the lip seal. Otherwise you need to go rope. Trying to trim/cut the rope to fit after you roll in the rope seal is very difficult under the engine. You also need to test the tightness of the crankshaft by turning it with the rods not connected after torqueing the main caps . There are also some tips on applying sealant and installing the two rubber dowels on the videos. If you have burned up a couple of rear rubber seals, hopefully the debris hasn't plugged up any oil ways. Rear main seals can be very costly lessons. One fellow I Jeeped with had his MB leaking badly. It was a blue trail of smoke behind him and a pool at every stop. He had just paid a mechanic $1000.00 to fix the leak!
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Green Disease, Jeeps, Old Iron!
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fullgarage
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Joined: 15 May 2020 Location: Celina, TX Status: Offline Points: 41 |
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Posted: 01 Mar. 2021 at 4:05pm |
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Thanks for the replies. The rear seals did not burn, they just leaked. Both looked fine when I removed them. I expect the crank journal is a bit small and that is why I want to go with the rope. From other posts, it seems that you can get a bit more clearance by removing the transmission and then pulling the seal through is possible. I guess what I am asking is how much better is pulling the engine and then totally tearing down the short block. I am good with a Bit of a drip but what I currently have is a mess.
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David - Celina,TX
1948 CJ-2a (on the road but never finished) |
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uncamoney
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Posted: 01 Mar. 2021 at 4:23pm |
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If you find that you need to travel with a drip pan you might have a problem. I was out to tour a B 17, drip pans under every engine.
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john
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Joe DeYoung
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Posted: 01 Mar. 2021 at 4:36pm |
IMO - Trying to do this job in the vehicle with the crank still in the engine is a complete waste of time an will lead to failure and you will still have a mess.
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Joe DeYoung
to many jeeps, parts, and accessories to list here, but apparently enough to keep me in trouble with my wife. |
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Stev
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Posted: 01 Mar. 2021 at 4:44pm |
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I recommend pull in the engine and doing this on an engine stand flipped so the crank is up. It can be done in the Jeep, but it is a pain and if you can't get everything perfect - it is just going to drip. If you don't have a lift this is a long weekend and do repair it with the engine in the Jeep, takes about the same amount of time pulling the engine.
Edited by Stev - 01 Mar. 2021 at 4:45pm |
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Stev
1946 CJ2A Trail Jeep (The Saint), 1948 CJ2A Lefty Restored |
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Oldpappy
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Posted: 01 Mar. 2021 at 5:26pm |
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I too would pull the engine for this.
Learned my lesson on that years ago. I successfully did it with the engine in the Jeep only once, but it only takes one failed attempt to decide it is a lot less work to just bite the bullet and pull the engine, and it is a whole lot easier to get it right with the engine on a stand. You don't want to spend that much time and work underneath a Jeep just to find it was wasted effort. Pulling the engine isn't difficult, especially if you remove the grill and radiator first.
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If you can't get there in a Jeep you don't need to be there!
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oldmansimek
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Posted: 01 Mar. 2021 at 5:33pm |
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If you are going to use the rope you really should pull the engine and crank to seat the rope correctly, however that is a lot of work and I have done it with the engine in on many vehicles and not had a problem or at least something you can deal with. Having said that I really don't think any are better then the other, if you have a good surface the rope, two piece rubber,or one piece rubber all seem to eventually leak or they don't I have had equal luck or lack there of with all three choices. Don't even get me started on scroll seals.
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Stev
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Posted: 01 Mar. 2021 at 6:04pm |
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One more thought that probably will not fix this issue, but something to try/ screw with before going for the rear main seal adventure:
If there is too much pressure in the crank case, it is going to put pressure on the oil seals and it can potentially force oil out of the rear main. So, the crazy idea is to take the PVC valve apart (it just unscrews near the middle of the valve into two halves). Clean the parts, ream any built up crud from the passages. Also check the hose from the air cleaner tube to the dipstick housing, it also needs to be clear of obstructions.
Edited by Stev - 01 Mar. 2021 at 6:06pm |
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Stev
1946 CJ2A Trail Jeep (The Saint), 1948 CJ2A Lefty Restored |
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WeeWilly
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Posted: 01 Mar. 2021 at 11:56pm |
Are these numbers correct? Why I am asking is both of the cranks I have out in my shop that I am using to build up 2 engines measure 2.312. One of them came out of a M38 with the neoprene seal the other a 48 CJ that had a rope seal. Jim
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47 CJ2A (Ranch Hand) 48 CJ2A, 48 Willys truck, T3C 3782, M274 (Military Mule)
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Joe DeYoung
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Posted: 02 Mar. 2021 at 1:09pm |
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As best to my knowledge, the current seals being made are made for Ø2.345 crank seal diameter. The 'old' seals were made for Ø2.312 crank diameter. I do not know when the change occurred but there definitely is a difference now. I don't know the exact reason for this but I'm guessing (and this is only a guess) the seal company's were having problems with cranks that were to large and burning up the seals. It would be interesting to see the mechanical drawings of the various crank shafts used to see what dimension Willys (Ford) were machining the crank seal surfaces to.
As anything we get after market now, parts should be verified as good before we install them. For the rear main rubber lip seals, I've made a fixture to simulate the block and main cap groove. I put the two halves into the fixture and measure the diameter with an optical competitor.
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Joe DeYoung
to many jeeps, parts, and accessories to list here, but apparently enough to keep me in trouble with my wife. |
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WeeWilly
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Posted: 02 Mar. 2021 at 3:05pm |
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Thanks Joe, I haven't bought any neoprene seals for several years but didn't have any problems in the past with them but if the new ones are of a different size it is good to get this info out to all our jeep friends. For those who are looking for a good rubber rear main seal Classic Military vehicle Parts (Jeep1942.com) sells a rubber seal that he says to be the right size and are the best made. These are made by Best Gasket Co. Jim
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47 CJ2A (Ranch Hand) 48 CJ2A, 48 Willys truck, T3C 3782, M274 (Military Mule)
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fullgarage
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Joined: 15 May 2020 Location: Celina, TX Status: Offline Points: 41 |
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Posted: 05 Mar. 2021 at 6:49pm |
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Well, here is the update. I decided to pull the transmission and transfer case since I had a small leak coming from the front of the transmission anyway. I am lucky to have a lift, so removing the transmission is pretty simple. I then removed the main caps which allowed the crank to drop about 1/4 inch. I ordered the best seal from Walcks which is a much higher quality seal than the FelPro and did not fray as easily. Using a sneaky Pete and the seal coated in assembly lube, I slowly pulled it through while a friend turned the crank with a wrench. I then re-installed the front two main caps to pull the crank up into place. I could then carefully trim the excess. Cutting the edges turned out to be the hardest part of the process as it was very hard to get a razor blade into the small space. Probably took me an hour to get it all trimmed, but after that it was just straightforward reassembly.
I got it all together last night and let the permatex cure overnight. I filled with oil today and took it for a test drive. No leak so far, but time will tell. if it leaks again, I guess the engine will need to come out and the crank removed. Thanks to everyone for their help!
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David - Celina,TX
1948 CJ-2a (on the road but never finished) |
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fullgarage wrote: