About to replace rear main seal (in frame) - Looking for tips/advice

[2nd Scout]

This thing leaks like a sieve. I have figured out that I lose a quart every 300 miles or so, on average. It appears to be coming out right between the flywheel housing and the back of the oil pan. The bottom of the rig is coated in oil, and I leave a little puddle where ever I park. I replaced the pan gasket first, and that didn't do it. I installed a crankcase ventilation system with catch can, that goes into the intake ahead of the turbo, and that didn't help either. I have tried stop leak, different oils, and nothing seems to help. I get some white puffs out of the draft tube, so it is not blocked. The rear main seal is next on my list.

I have never done this before. Looks like you drop the pan, pull the rear main bearing cap, push out the old seal, push in the new one, replace the bottom one and reassemble. I have seen some references to #2 Aircraft Sealant, but not sure if it is necessary or what to do with it. I also don't know what is entailed in getting the bearing cap off.

Any tips and words of wisdom before I do this would be appreciated. I would like this to be done right the first time, if possible. I have a service manual, but I would like advice from you also. I do have a complete set of Nissan gaskets.

Thanks in advance for any help!

[CareyWeber]

Originally Posted by 2nd Scout

This thing leaks like a sieve. I have figured out that I lose a quart every 300 miles or so, on average. It appears to be coming out right between the flywheel housing and the back of the oil pan. The bottom of the rig is coated in oil, and I leave a little puddle where ever I park. I replaced the pan gasket first, and that didn't do it. I installed a crankcase ventilation system with catch can, that goes into the intake ahead of the turbo, and that didn't help either. I have tried stop leak, different oils, and nothing seems to help. I get some white puffs out of the draft tube, so it is not blocked. The rear main seal is next on my list.

I have never done this before. Looks like you drop the pan, pull the rear main bearing cap, push out the old seal, push in the new one, replace the bottom one and reassemble. I have seen some references to #2 Aircraft Sealant, but not sure if it is necessary or what to do with it. I also don't know what is entailed in getting the bearing cap off.

Any tips and words of wisdom before I do this would be appreciated. I would like this to be done right the first time, if possible. I have a service manual, but I would like advice from you also. I do have a complete set of Nissan gaskets.

Thanks in advance for any help!

I'm sure it has been done, but there are differences see pic.

[David Dixon]

Hey Carey, I think you missed!

You've pretty much got the idea. The aircraft sealant comes into play when you are replacing the bearing cap. The bearing cap fits tightly into the block and has grooves on either side for two short straight bits of gastket/seal like rubber on each side. A bit of aviation goo helps with the seal here. These two ~inch long pieces should come with the rear main seal.

Removing the bearing cap requires that you remove the two bolts and then use same bolts or like metric thread bolts to bolt on something that you can yank on. I used a strap of some sort and a hammer or a slide hammer. It may require some ingenuity and patience to get the bearing cap out while under the truck. Do whatever you can to safely give yourself as much room as possible under there - jackstands or such.

It can also be a fight to remove the bottom half of the old seal. I got good results by hammering some sort of plastic rod (part of the old top seal?) in to push it out the other side and then grabbing it with pliers. There is a tool designed for this called a "sneaky pete." I tried it and it didn't help much, other folks swear by 'em.

Get comfy and store up on patience and it won't be too bad a job.

-David

[CareyWeber]

Originally Posted by David Dixon

Hey Carey, I think you missed!


-David

Hey I resemble that...

[1977ScoutII]

Buy two seals. When you destroy the first one going in, you'll have a back up. If you get lucky and get the first one in without damage, you can take the other one back.

[2nd Scout]

Should I really get two sets of seals or are you joking?

[David Dixon]

I don't think that there is much risk of mashing the new seal. Lube it good and tap it in gently and it should be fine. Plus, they are lightweight and you could always get one overnighted if you HAD to get your rig back on the road.

[2nd Scout]

Thanks for the replies, they have been helpful. When I find a day to tackle this, I'll let you know how it goes.

[2nd Scout]

Doing this job tomorrow at my friend's shop (on a lift). I drop it off this evening, so we can let the oil drain all night. Hopefully this will minimize the oil drips on our heads. I'll let you know how it goes. Thanks for your help.

Oh, does anyone have the torque specs on the bearing cap bolts handy? I seem to have misplaced my manual.

[2nd Scout]

Well, everything went back together beautifully and oil poured out through the new seal after we cranked it up. It was a little tight rolling the new seal in the top, but nothing that anyone thought was a problem. I had two professional mechanics helping me do this. I just ordered two more sets of seals and this time we are going to loosen the crank a little more (loosen more caps) to try and get the top half to go in more easily this time.

Getting that bearing cap off was a real pain. I am not looking forward to doing that again.

Any ideas on what we may have done wrong? All I can figure is that the top half of the seal got messed up going in. I am assuming it didn't get put in backwards. I didn't do that part myself, so I am not absolutely sure.