Another 340 rear main seal

[bandt]

Hi Guys,

Read as many posts as I could find on the subject.
have to replace my rear main seal on my 340. I am looking for some solid advice on being able to get away with doing it once. The engine is out in a stand, the pan is off and I have no idea other than what I have read on the subject. I bought a full Felpro 340 gasket set. The rear main is 2 rubber pieces 1 with ears 1 without. I also bought a tube of "The Right Stuff" I read was good stuff.
Please any advice would be appreciated.
I'm a bit stressed about it.

[Topcat]

Years ago, I had to replace my rear main seal on my 340 I had at the time. I dropped the oil pan while the car was on jack stands. Then I un bolted the rear main cap. After that, I used a pair of needle nose pliers and grabbed the upper rear main seal half up above and slowly slid it out.

Took the new one and put some oil on it so it could slip back in for the install. Went right in.

Next, cleaned the ends off with laquer thinner where it would be siliconed to the bottom half. Siliconed the ends with a little and re installed the bottom half with the other new seal. Then installed rear main cap and re torqued. Leak was gone and I didn't have any problems with it after that.

[Topcat]

When you re install the cap, make sure to coat the bearing surface with a little Molybendum just for insurance. Make sure the bearing is real clean and that no dirt got on it while it was out.

[bandt]

Thanks topcat,

What is molybendum? I'm assuming some sort of lubricant. I read somewhere you have to seal the main cap where it mates to the block is that correct? The engine won't be fired for a while so should I use grease instead of oil on the seal lip?

[Topcat]

Thanks topcat,

What is molybendum? I'm assuming some sort of lubricant. I read somewhere you have to seal the main cap where it mates to the block is that correct? The engine won't be fired for a while so should I use grease instead of oil on the seal lip?

Pronounced Molidium. a black/graphite colored grease commonly used in lubrication.  I didn't seal the main cap. As far as I recall, it's a machined surface so it doesn't require and sealing where they mate up. Light grease on the seal lip is O.K.

[Chryco Psycho]

make sure you do not peel the outside lip of the seal when you slide it in , a small piece of plastic may help it slide in , I offset the ends of the seal slightly on most but with the side ears you cannot do that , a small dot of right stuff can glue the seal ends together where they meet & make sure the lip is pointed inward or it will leak

[bandt]

Would I be better to clip the ears off to allow the seal to offset, or just use it as is?

[Chryco Psycho]

use it as it is

[72cudamaan]

As added insurance , I always put a light film of anaerobic sealer on the mating surface of cap to block. It wont effect your clearances at all and helps to seal any minute imperfections in the casting.

[bandt]

Thanks for the input guys.
Still a little hesitant but I'm gonna try it. It would just suck to have it leak after it goes back in the car. This is as easy as it's going to get, sitting in a stand staring right up at me.

[bandt]

Just got my 340 fired up after quite a while.

Was only running for a few minutes, small 2" puddle right under the bellhousing. Installed the new rear main while the engine was in the stand. Made sure everything was clean, seal was facing the right way, used "Right stuff" on the seal ends. Put a little grease on the lip so I didn't burn it up on start up.

Is there anyway it has to break in a little to conform to the crank? I'm trying to pretend it is going to stop, but I think if it was going seal it would have right from the start.

I haven't won many battles with this car.

[Aussie Challenger]

If you were as careful as was explained to you it could be another leak like from the rear of the cam or the plug for the main oil gallery, remove the cover and have a look with a light, you might have to clean inside the back of the block and run for a minute to recheck leak. Also check the back of the rocker cover and oil pressure switch.

[72cudamaan]

OHHHHHH NOOOOOOOO!!!!!  what happened.        

I guess we didn't mention look at other sources for leaks while it's out.   

[Bullitt-]

Look at the block just behind the intake manifold for oil...I had two mechanics tell me I needed a rear main but it turned out to be a bad install of the rear intake manifold gasket. The oil drips off the center of the transmission directly under the rear main.

[bandt]

Thanks guys,

I'll have a look in all the spots you guys suggested. I gotta catch a break sooner or later, don't I?

Brian