The Stovebolt Site Forums The Shop Area Engine Shop Rear Main Seal

I dont know if this is the right place to ask about this problem because its not a GM problem but some one may be able to help. I have a 53 Jeep M38A1. I got this Jeep after it had sat for some time and when i started it the RMS"rear main seal" leaked.It had a neoprene seal so i replaced it. It leaked so i was told that a rope seal may hold better so i pulled the engine and put one in.It leaked. I now fill like i did a rush job with the rope seal. The engine was rebuilt and had low miles but has sat so the crank is good as are the main bearings. I have a 46 jeep thats engine had 0 miles when i got it. Its RMS leaked. I replaced it and it didnt help.I did a frame off rebuild and replaced the RMS and it stoped leaking.I thought maybe it had alot of crank case presser but it dosent. I have worked as a mechanic on and off for 40years and replace RMS on alot of diffrent kinds of engines and never had a problem.I want to drive it this summer but i dont want to repeat the past.I am thinking about trying another rope seal.What would you do?

If you did not put a tiny amount of sealer on the brg,. cap from the edge of the seals out it could be leaking between the block & cap. If the flywheel bolts go into thewet side of the crank it can leak through the bolt threads. You will need some sealer on them. The plug at the rear of the camshaft can leak & be mistaken for a RMS. I prefer the rubber type seal when available.
I don't mind questions about other makes as long as it is not a foreign vehicle.

Most people have forgotten (or maybe didn't know in the first place) that rope seals need to be thoroughly soaked in oil before installation. The oil helps the fibers swell up and make a smooth, tight seal against the crankshaft. I soak rope seals overnight in clean 10W-30 motor oil before installing them.
Jerry

Rear main seals are kind of an age old problem on Willys vehicles. I have experienced the frustration of working on them in the military and later on my own vehicles and in shops. The last one I replaced on an M38 was a neoprene seal and it has lasted for several years. I have also found that parts offered by some of the military suppliers are NOS and could be 50 years old. In some cases parts have been so hard or brittle they don't work very well. Midwest Military and Ron Fitzpatrick are good sources.
Fred

I think i will pull the engine and maybe presserise the oil system while its out and let it set at a angle to see if it will leak. Fred i have heared about the RMS they are a problem I wonder why? I like old orignal jeeps but if this jeep didnt have a engine i wouldnt look for one like it has.

Rear main bearing seals are not exposed to pressurized oil- - - -splash only! Be sure the drain holes back into the pan are clear and the tip about using Permatex between the main cap and the block is a good one.
Jerry

Make sure that it is the rear main seal that's leaking. I had a serious leak from the front of the transmission on my 47 CJ2A.
It's different oil but basically leaks from the bellhousing in the same location as the rear main. They could both be leaking.
Fred

Its engine oil for sure. What made your trans leak?I am thinking about starting it up on the ground after i replace the seal.

It was overall sloppy but I discovered later that it needed a full gasket between the trans and the bellhousing. It was mostly the cluster gear shaft/case leaking. Later units only used the gasket behind the bearing retainer. My 2A has a "F" head engine same as your 38A1 but it didn't leak too bad so I left it alone.
Fred

If possible use a seal from Best gasket company. They sell rope that really works, like the old stuff did.

Joe

I drove it some the last 2 summers like this but i let the license run out telling my self i wouldnt put it back on the road untill i fixed it. I have 3 prodjects ahead of it. My dads tractor needs rewired,my 61 F600 has a rear hub leaking oil and i bought a Case skid steer that needs a engine.Its sometimes overwhelming haveing so many old rigs i may thin them out some.