Rear Main Seal

^^^And if you install the right seal it won't, after installing 4 I wonder how I'd know that

Doing mine this or next week... need one that doesn't leak, so I'm subscribing.

I used the felpro 2941 installed dry ( that's they way they call for it), it leaked a tiny bit for few miles didn't keep an eye on how many miles but I was pissed, it didn't leak as bad has the old one but it was new and it ticked me off. after some drive time like I stated it doesn't leak anymore, the area is dry, must need to swell up or seat . this was close to a year ago and still no leaks. I finally got my new T5 done not to long ago and that got rid of my leaky, clunky stock T5 .. now my garage floor is free of cardboard, nice, clean & dry under her

The teflon seals take excessive heat better and tend to last longer. I still put a thin coating of permatex black around the seal then tap it in place, this has proven to be a leak free method for me after letting it sit overnight. When I build motors I put the seal on before I torque the cap down, this has been a god send in preventing leaks...

So the Teflon lined one with a thin coat of permatex around the outside and let it set up over night???

Rick ftw....

I'd trust him.

25thmustang said:

So the Teflon lined one with a thin coat of permatex around the outside and let it set up over night???

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Yeah if I have to replace one on a motor that is together that is what I do. The key is making sure the area is clean and make sure you do not destort or damage the seal when you tap it in, I deburr the block and rear cap since they are usually sharp and shave the outisde of the seal as you tap it in. Put a very thing coat of oil on the crank with your finger so you don't damge it while you tap it in, just make sure it doesn't drip in your seal area.

Once of my buddies learned to pack the rear side of the seal with grease first then tap it in, I had limited success with that method but a old timer he worked with swore by it....

They also sell "double lipped" seals, usually run on cars with vac pumps only but I would assume this would work well on a reg application also. It does require a special install tool, or atleast it is recommended.

I will probably do as you suggest Rick. Sounds to be the most straight forward way, and if I take my time and do it right should get what I'm looking for (no more leak).

Mustang5L5 said:

There is a little "wear-in" that does take place. A lot of guys suggest to lightly sand the crank with sandpaper to roughen it up and allow the seal to wear in a new "seat"

I've also heard of seals that position the seal in a different spot so that it wears in a new location.

Also, install tools can make a difference. There is a $100 RMS instal tool...but I used a $1.99 4" PVC knock-out cap for mine i got at home depot.

Also, PCV systems can cause the RMS to blow out oil if the crankcase is pressurized. So make sure your setup is running correctly


I don't have a clear answer on this though. I haven't even started my engine yet to see if my latest install leaks or not

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I used some emery cloth to smooth up the crank, and the checking the pvc system is a great idea. I replaced my screen and valve when I did my intake.

Rick 91GT said:

The teflon seals take excessive heat better and tend to last longer. I still put a thin coating of permatex black around the seal then tap it in place, this has proven to be a leak free method for me after letting it sit overnight. When I build motors I put the seal on before I torque the cap down, this has been a god send in preventing leaks...

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I should have clearified my fault, I did use rtv on the O.D. but left the I.D. dry, this was the area I ment to leave dry, must have to do with the teflon or something. I know on the rubber rear mains some guys would use motor oil or grease them( I.D.).