Engine Rear Main Seal: Sleeve or no sleeve

Mustang5L5 · Jan 23, 2020

I have the old RMS out and about to install a new rear main seal. Just wondering if i should install a sleeve here as well?

I have 100K on the crank/block. I replaced a leaky RMS about 2K miles ago when i did a 5-spd swap. When i pulled the motor a couple months ago, the seak i had previously installed was seeping, but not leaking a whole lot. PCV and other parts are all new, so i don't think i have a crankcase pressure issue on my N/A motor.

Anyway, I have a Ford Racing M-6701-B302 seal, which i believe is OEM since the seal itself has an F1SE part number on it.

I also have a Felpro 21-2100 crank seal, and the Felpro 16300 sleeve install tool.

I've inspected the crank the best i can, and possibly see a wear groove around the circumference. But, the previous seal was leaking a little. Should i install the sleeve? Any downside to installing the sleeve if it wasn't needed? I read it scored the crank, so you will always need to use a sleeve on it.

JD1964 · Jan 24, 2020

Could have been leaking from the surfaces where the main cap meets the block. Have you considered that?

Wayne Waldrep · Jan 24, 2020

I learned on the balancer that it only takes a very minor groove to cause a leak. It doesn't even have to look like much. I also think the tolerances in the crank surface and seal both could use the sleeve thickness to make up any differences that might add up.
That's just my thoughts. I've never used one but like I mentioned to ya, I'd like to do this very thing to mine at some point.

Mustang5L5 · Jan 24, 2020

i Can definitely see a wear groove. I can’t feel it, but you can see where the seal rode.

I’ll sleeve it. The last seal didnt seal do why not?

Next time I do this will be on a new 347 bottom end...if I ever do this again

Wayne Waldrep · Jan 24, 2020

Can you take a pic of the metal sleeve in your hand or something. Every pic online just looks like a rubber band. And any other picture would be great.

Mustang5L5 · Jan 24, 2020

I could..but too late. I installed it.

It’s thin, but definitely not a rubber band. With the tool and dead blow hammer it was easy to install

Wayne Waldrep · Jan 24, 2020

Bird76Mojo · Jan 25, 2020

I prefer the offset lip seals over these sleeves. Like the Engine Tech S4686. They've always served me well.

Just another option for you...

Potomus Pete · Jan 25, 2020

I have a never ending leak on the rear main seal . Very little info on the forums about the sleeve . I fixed all leaks but this one. Last seal I put on was teflon , and it leaked the same day I started the car. Lets see if its going to leak it probably will leak soon.

Mustang5L5 · Jan 25, 2020

Here are the wear grooves I found on my crank. You can’t feel anything, but at certain angles you can see this.

So I sleeved it. Was easy.

This was a couple drops per drive leak. Enough to annoy me, but not enough to justify pulling the trans and fixing until I had the engine out anyway.

New sleeve, seal and pilot Bearing now . Crossing fingers this does the trick

Blown88GT · Jan 25, 2020

Potomus Pete said:
I have a never ending leak on the rear main seal . Very little info on the forums about the sleeve . I fixed all leaks but this one. Last seal I put on was teflon , and it leaked the same day I started the car. Lets see if its going to leak it probably will leak soon.

Mine, too, never ending. Original leaked, replacement leaked.
I need to find someone experienced with these to fix it.
I found some local guys that do nothing but Fox Bodies. Saw some of their work at a car show.
Cobra engine transplant into a 4-eye.

Shakerhood · Jan 27, 2020

Mine leaks too but mainly over the winter while its stored away, once I start driving again in the Spring and Summer it will stop.

skiwesser11 · Jun 7, 2021

How did the sleeve work?
I’m putting same one in my 1988 gt now, I used the 2941 seal but had to oil it, I guess due to the slightly larger diameter of crank due to sleeve.. hope oiling it doesn’t matter… was definitely a little tighter to work (tap) in than before..

Sure hope it works, mine has also had a small leak for years, last time trans or engine was out I hadn’t heard of these sleeves. Thanks

Mustang5L5 · Jun 7, 2021

No update yet. Engine is in the car, but i haven't started it yet

Prime Lord · Apr 28, 2025

Zombie thread!

It appears you can't get the Fel-Pro installation tool anymore. How hard do you thing it's going to be to put the sleeve on without the tool? I have the small plastic mallet to tap it into place, but it's going to be a slog I think.

Noobz347 · Apr 28, 2025

Do you have a set of [big] sockets?

nickyb · Apr 28, 2025

Try matching up a Pcv pipe to the sleave

Prime Lord · Apr 28, 2025

Noobz347 said:
Do you have a set of [big] sockets?

Nothing THAT big.

Prime Lord · Apr 28, 2025

nickyb said:
Try matching up a Pcv pipe to the sleave

That's a reasonable idea. Chunk of 4" PVC Pipe with a cap on the end.

90trunk · Apr 28, 2025

Prime Lord said:
That's a reasonable idea. Chunk of 4" PVC Pipe with a cap on the end.

We used as PVC cap or pipe plug as an install tool on my repair sleeve. Worked great...Home Depot to the rescue.

Engine Rear Main Seal: Sleeve or no sleeve

Mustang5L5

That is…until I whipped out my Bissell

JD1964

there is enough sticking out to grab on to

Wayne Waldrep

Before I post a pic, do you have one of yours?

Mustang5L5

That is…until I whipped out my Bissell

Wayne Waldrep

Before I post a pic, do you have one of yours?

Mustang5L5

That is…until I whipped out my Bissell

Wayne Waldrep

Before I post a pic, do you have one of yours?

Bird76Mojo

Potomus Pete

I'm still waiting for the fully nude shots

Mustang5L5

That is…until I whipped out my Bissell

Blown88GT

Shakerhood

skiwesser11

Mustang5L5

That is…until I whipped out my Bissell

Prime Lord

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Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

nickyb

I gotta say i never painted my nuts, Never Ever

Prime Lord

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Prime Lord

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90trunk

Active Member

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Engine Rear Main Seal: Sleeve or no sleeve

That is…until I whipped out my Bissell

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That is…until I whipped out my Bissell

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That is…until I whipped out my Bissell

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