AMC 360 Rear main seal

[Anvil-3]

I replaced a dripping rear main seal twice now that’s worse than it was originally. It seems like there’s not a lot of options out there and a lot are out of spec. It’s totally stalled my progress as I’m getting tired of replacing the seal over and over for no reason.

Does anyone have a recommendation for a good brand or P/N that reliably seals?

(89 grand wagoneer - 360/727)


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[letank]

The only thing is that you may need a little more sealant on the corners, or may be it is your oil pan seal that is not doing its job because the bolts hole have been slightly deformed and the oil pan gasket cannot pick up the slack.

Add some dye, run the engine at idle for 1 or 2 min and see where the dye is more apparent.

The RMS I bought is usually from the big parts store and probably a Fel-Pro. I usually get 2 because sometimes the engine block is so sharp I had cut a sliver of the seal.

Otherwise your crankshaft could be wobbly, any fore and aft motion that is over 1/4" when you grasp the harmonic balancer with your hands and try to push/pull. That would be the thrust bearing going south, it can be fix by a weld and turned at a crankshaft repair place.

[tgreese]

Regarding brand, Fel-Pro is the industry standard. I see four brands here https://www.rockauto.com/en/catalog/jee ... +seal,5604 - Mahle and Victor are good and well-known brands, and possibly are the same part as the Fel-Pro. All are rubber. There's also the EngineTech seal - same price, but made of polyacrylate. They have a video for the polyacrylate part that may convince you - sorry, no personal experience. Kinda think any of these, properly installed, will work well.

Some engines can use a rope seal. These engines came with a two-piece rubber seal from the factory and cannot accept a rope seal.

The procedure is covered at page 9-175 of the '89 TSM. Free to read and download at the Tom COllins site. Suggest you review the procedure there and verify your methods.

[Stuka]

I have just used the Fel-Pro part.

The big key thing to do is to remove ALL oil from the surfaces the seal touches. Typically I use brake clean. If there is any oily residue, the seal won't seal, and any RTV used won't seal either.

[Srdayflyer]

are you using felpros removable oil pan support pins,they screw into the oil pan bolt holes allows you to have the oil pan just supported enough to start all the bolts except the 6 support pins which you remove ,then you can tighten the pan without having to do a balancing act, and allows 1 man (easy ) install. ive used these on several oil seal replacement jobs best 10 bucks ive ever spent, got questions i can get you the p/n

[Anvil-3]

I have just used the Fel-Pro part.

The big key thing to do is to remove ALL oil from the surfaces the seal touches. Typically I use brake clean. If there is any oily residue, the seal won't seal, and any RTV used won't seal either.

Mm that is likely the issue on the rear main. I have all new felpro rear seals to install and will do that. Regarding the pan I finally got a new pan that should solve that leak, I think the sealing surface is just too warped to seal well


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[Anvil-3]

For those interested, I got a new pan and cleaned and reinstalled the rear main seal. Seems to have fixed everything, the new pan in much much tighter at front and rear than the old one. So much better. Thanks for the help everyone


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[Greg72]

For those interested, I got a new pan and cleaned and reinstalled the rear main seal. Seems to have fixed everything, the new pan in much much tighter at front and rear than the old one. So much better. Thanks for the help everyone


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Congrats!!!

Just out of curiosity... were you able to do the rear main by pulling the oilpan only....or did you have to pull the entire engine? I've got a leak back there somewhere on my '89 (either valve cover gaskets or rear main... but probably rear main) and I've been avoiding it completely thinking that the entire engine had to come out.

How difficult of a job did it turn out to be.... ?


-G

[Anvil-3]

For those interested, I got a new pan and cleaned and reinstalled the rear main seal. Seems to have fixed everything, the new pan in much much tighter at front and rear than the old one. So much better. Thanks for the help everyone


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Congrats!!!

Just out of curiosity... were you able to do the rear main by pulling the oilpan only....or did you have to pull the entire engine? I've got a leak back there somewhere on my '89 (either valve cover gaskets or rear main... but probably rear main) and I've been avoiding it completely thinking that the entire engine had to come out.

How difficult of a job did it turn out to be.... ?


-G

Pulling the rear main required me to pull a section of exhaust (collector?) and the oil pan and rear bearing cap. It’s a 2 piece seal so no need to pull the engine. Through my difficulties I spent more time on oil pan bolts than anything. Definitely wouldn’t pull the engine unless you have other major issues to contend with


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[Anvil-3]

For anyone who cares.... still leaking from the rear main seal while running pretty significantly, I'm still pretty confident it's been an issue on my end as it was hardly dripping in the first place and I just had to go and fix it. Someone somewhere had mentioned a way to polish up the mating surface of the seal to the crank.. has anyone done this? going to reattempt this once I get through some other odds and ends as I am not driving it more than a mile or two at a time for testing.

does anyone have a picture or reference for which way this seal should be facing? Yes, I've read the TSM, I don't find it to be super clear and after having replaced it a couple times I'm not sure putting it back in the way I just did it will be helpful, I may have screwed it up previously

[Greg72]

For anyone who cares.... still leaking from the rear main seal while running pretty significantly, I'm still pretty confident it's been an issue on my end as it was hardly dripping in the first place and I just had to go and fix it. Someone somewhere had mentioned a way to polish up the mating surface of the seal to the crank.. has anyone done this? going to reattempt this once I get through some other odds and ends as I am not driving it more than a mile or two at a time for testing.

does anyone have a picture or reference for which way this seal should be facing? Yes, I've read the TSM, I don't find it to be super clear and after having replaced it a couple times I'm not sure putting it back in the way I just did it will be helpful, I may have screwed it up previously

Bummer. So it's worse now that you messed with it? Any chance that you tore the new seal putting it in? It seems like a few people reported that the installation is somewhat delicate.


-G

[Srdayflyer]

here's the question, did you loosen up ALL , ALL the main caps the manual calls if i remember to do this not a whole lot but enough to drop the crank to allow a smooth removal and installation of the new seal halfs especially the upper seal half, and the lips of the seal should face forward so when there is crankcase pressure the seals lips are forced backward and gripping the crank journal forming a tight seal . then you install the rear cap with the lower seal use just a little hitemp rtv on the mating surfaces of the seal,making sure the seals are clean(no oil) when applying the rtv. are you using snap pins to hold the oilpan in place when installing the pan and gasket and installing the bolts make a hard job easy , OBTW dont forget to re torque the main bearing caps, and allow the rtv to cure for at least over-nite and dont add oil till the cured rtv is setup. i can get you the snap pin part# if needed i got them at a-zone. jegs also has them. iv'e never had an oil leak if you follow this guideline, it whats called out in the manual albeit a bit confusing if you havent done it before or helped someone do it, hope this helps

[Srdayflyer]

obtw, i had to do this on my 360, as it was a rebuilt motor, unfortunately it sat 10 years the seals hardened and to a set and the motor leaked from the rear main, iv'e replaced numerous seals in all types of motors, including rope seals in buick 350's anyway wishing sucess on the 3rd try , its a charm

[Anvil-3]

obtw, i had to do this on my 360, as it was a rebuilt motor, unfortunately it sat 10 years the seals hardened and to a set and the motor leaked from the rear main, iv'e replaced numerous seals in all types of motors, including rope seals in buick 350's anyway wishing sucess on the 3rd try , its a charm

That snap pin part number would be great, I’ll take these notes along with the TSM for the next go


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[Srdayflyer]

i'll get it for you tomorrow or sunday with a pic, they screw into the bolt holes, 6-8 of them , in a package . you push the pan bolt hole thru the snap pins they hold the pan in place while you start the pan bolts then just unscrew the snap pins and install the remaining bolts tighten and torque panbolts easy peasy

[Srdayflyer]

Fel-Pro Oil Pan Snap-Ups
Part Number: 375-ES72863