79 v8 rear main seal

[radman]

here i go again! my jeep journey has now brought me to the rear main seal leak. i have noticed that the replacement seal appears to be two pieces, which used to mean that one could replace them with the engine still in the car. is this true and are there any special tools, parts or knowledge necessary to perform this job?

thanks in advance... radman

 

[CJ]

Nope - They change out just like any old rear main. Drop the pan, remove the rear cap, spin out the old seal in the block, replace, retorque and reassemble. If you have done one you have done just about all of them

Good thing about the CJ is you have plenty of room to work!

 

[coldwater]

I would just add, BE CAREFUL when you slide the new upper into place! One little knick in that seal, and you'll be ding that job again!

 

[Petescj]

On the two "feet" of the seal dab a small admount of silicone. Mine wouldnt stop leaking with the new seal till I did that.

 

[brn371]

I have the same rear main leak, but do no want to replace until our very long off season. Anyone have any thoughts on the new bars leak main seal leak oil additive?

 

[CJ]

The stuff works by making all the rubber gaskets exposed to the additive swell. It will kinda help (sometimes it doesn't do anything) for a while but eventually you will need to change the seal.

 

[coldwater]

I have the same rear main leak, but do no want to replace until our very long off season. Anyone have any thoughts on the new bars leak main seal leak oil additive?

Whelp. It may, or may not work, but there is a price to pay, being It's a quick, temporary kind of fix. Thet would like you to believe that the product will "condition" the seal, when really what it does is basically rot it. The seal softens to the point it can become like snot, and will eventually fail anyway in most cases. The other issues is that it will "condition" every seal it comes in contact with. If you are going to do the job anyway, then I guess It's OK, But If It were me, I would just take the day and do it right.

 

[AdamH]

I am currently on my 3rd rear main. 1st one installed when I rebuit the AMC 304 out of the Jeep. 2nd and 3rd times did it while engine was in the Jeep. I still have a leak. Now it has gotten better after each time but won't go away! the 3rd time I had my bro-n-law install it while I watched. He builds engines for a living. Not sure what to do now!

 

[coldwater]

Rear mains are one of those leaks that can make you want to jump off a bridge. And Welcome to the site Adam.

 

[AdamH]

ok, getting tired of the leak. all of the past ones have been made by FelPro. any other brands out there to try??

 

[CJ]

ok, getting tired of the leak. all of the past ones have been made by FelPro. any other brands out there to try??

Interesting! I just checked Summit, Oreiley, Autozone and Advance - they ALL only carry Felpro.

I have never had my FelPro gasket leak on my 8 - you sure you don't have a small groove in the crank?

Have you tried the factory one from the dealership?

 

[AdamH]

Interesting! I just checked Summit, Oreiley, Autozone and Advance - they ALL only carry Felpro.

I have never had my FelPro gasket leak on my 8 - you sure you don't have a small groove in the crank?

Have you tried the factory one from the dealership?

nope, only used Felpro ones. wonder how much a factory one would cost?? as far as the crank, it was brand new when I built the engine and when we were putting it in, we checked to ensure there wasn't any damage to it but I guess we could have missed something small. At this point I may give replacing the seal one more try before pulling the engine. (it only has 100 or so miles on it since the build.)

on another note, I have read that some loosen all the cap bolts when replacing the seal. Why would you do this? I have only been taking the rear cap off; havnt touched the other caps.

 

[CJ]

nope, only used Felpro ones. wonder how much a factory one would cost?? as far as the crank, it was brand new when I built the engine and when we were putting it in, we checked to ensure there wasn't any damage to it but I guess we could have missed something small. At this point I may give replacing the seal one more try before pulling the engine. (it only has 100 or so miles on it since the build.)

on another note, I have read that some loosen all the cap bolts when replacing the seal. Why would you do this? I have only been taking the rear cap off; havnt touched the other caps.

You have only 100 miles on a new crank and have had to change out the rear main already (more then once)???

There is some thing really wrong. I have 35k of very hard miles on my FelPro seal and it is water tight!

How many times have you changed out the seal and where did you get a new crank from? The only 'new' cranks I know of are aftermarket forged and I'm not even sure they make them for a AMC 304 (I'm assuming you still have the factory engine)...

Can you give more info? Engine size and where you got the crank?

As for loosening all the main bolts? Never done that before...

 

[AdamH]

LOL wasn't thinking straight when I typed that! Had some minor surgery and I guess the pain meds were messing with me

Original AMC 304 with original crank. I was thinking about the new cam when I typed above. The machine shop cleaned and checked the crank and gave it a thumbs up. We were careful installing it so I highly doubt there is an issue with it. I did install a new oil pan... wonder if it is warped or something? I painted the engine AMC blue and I can't find any other leaks on the engine such as one of the valve covers leaking and looking like it was the rear main so that leads me to believe it is the rear main.

 

[CJ]

It's easy to over tighten the oil pan and mess up the oil pan gasket. Could that have happened?

Also, I have seen the upper seal installed backwards before.

 

[AdamH]

gonna try it one more time this weekend.... wish me luck.

 

[CJ]