Rear main seal what works?

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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thomas68
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Rear main seal what works?

Post by thomas68 » Sun May 08, 2022 7:13 am

I have the dreaded leaking rear main seal on my 44 MB. I have researched here about the best options. Is there a sure fire fix? I am not looking for a debate, but what others have done that works to fix the leak. Please let me know what has worked to cure the leak for you.

Thanks in advance.

Tom
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Re: Rear main seal what works?

Post by Bangle 99 » Sun May 08, 2022 9:21 am

I have a rope seal in mine and it doesn’t leak.


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Re: Rear main seal what works?

Post by '42 Peep's Motorpool » Sun May 08, 2022 9:28 am

Hi,

It might help to tell us a little about your problem:

1. Is the seal neoprene or is it a rope seal?

2. Did you trim the rubber rear cap dowels, and if you did, you didn't cut them flush with the block did you? (doing so prevents the rubber from being expanded to seal better). Did you apply any sealer to the dowels when they were installed?

3. Has the engine had any run time/miles on it, or is it newly rebuilt & leaking without having ever run?

A good seal is a good seal, regardless of material. Do you happen to recall which seal you installed? There were some defective neoprene seals around in the not too distant past.

I think the only way to 'cure' the leak will be a replacement seal, but if you end up going down that route, be sure that the crank seal surface isn't undersized or grooved/pitted. Because if it is, the problem will persist over and over again.

I also recall that some people have had excess oil not drain away from the rear cap because they were missing the short tube that reaches down towards the oil pan. Do you recall if this tube was fitted to the bearing cap? They are pinned in place but sometimes missing.

Good luck! :)

EDIT: I should mention that a transmission leak from the front bearing can allow oil to run into the bottom of the bellhousing, and it will weep/drip from the hole at the front of the bellhousing (just behind the engine). I'm sure you know where the oil is coming from, but I thought I would mention this because in a few cases people thought they had rear main seal leaks, but the leak ended up being from the transmission instead. Gear oil and engine oil will of course be different in viscosity and odor.

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Re: Rear main seal what works?

Post by irakli » Sun May 08, 2022 10:35 am

JMP seal worked for me after a lot of try/error attempts.
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Re: Rear main seal what works?

Post by thomas68 » Sun May 08, 2022 10:39 am

It is a neoprene. It was rebuilt about 18 years ago and just now started. I do have the drain tube installed. I will double check on the transmission oil. I was just wondering which way to go when I replace it, rope or neoprene. I read about the "bad" batch of lip seals, but didn't know the time period they were from. It seems like the rope would be a little more forgiving, but harder to install.

Thanks again, looking to hear more opinions on what worked for others.
Tom
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Re: Rear main seal what works?

Post by '42 Peep's Motorpool » Sun May 08, 2022 7:35 pm

Hi,

I used a NOS rope seal purchased from Mike Stopforth, but he tragically passed away in an accident a few years ago. It's held up well though, and the installation process wasn't bad. I soaked my seal for a couple of days (because I wasn't in a hurry) in clean engine oil, and then bent it around a little so it would not be too stiff to conform to the seal groove. It's been several years now since I installed it, but I used a big old rivet I have as a mandrel and slowly rolled and worked the seal into the groove. Something like that anyway.

I wish I had made a video then, but I did not. My rebuild kit came with a Felpro rope seal, but I did not use it because I had the NOS one from Mike. [removed mistaken comment about another seal manufacturer to avoid confusion]
Last edited by '42 Peep's Motorpool on Mon May 09, 2022 5:12 pm, edited 1 time in total.

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Re: Rear main seal what works?

Post by Scrumps » Sun May 08, 2022 11:44 pm

Hi,

“JMP now make a rope seal too”

Nothing listed on their website, just their two part rubber double lips seal!

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Re: Rear main seal what works?

Post by '42 Peep's Motorpool » Mon May 09, 2022 5:11 pm

Scrumps wrote:
Sun May 08, 2022 11:44 pm
Hi,

“JMP now make a rope seal too”

Nothing listed on their website, just their two part rubber double lips seal!

Scrumps
Correct, an error on my part. JMP currently only sells the seal you mention.

Per the technical bulletin regarding the rear main seals (copied from Ron Fitzpatrick Jeep Parts listing for the Felpro rope seal: https://www.vintagejeeps.com/p-1903-cra ... elpro.aspx

"Automotive Engine Rebuilders Association, AERA TB2025

The AERA Technical Committee offers the following information on the rear main bearing seal caution on 1939-71 Jeep 2.2L engines. These engines are sometimes referred to as the F & L head engines.

During production of these engines, two different cylinder blocks were manufactured. The early cylinder blocks had a rope rear main seal installed in them while later production blocks had conventional type rear main bearing seal installed in them.

When assembly of these engines is taking place, make sure you have the correct type of seal will help prevent engine failure. If the conventional rear main seal is installed in the early blocks that require a rope seal, there may be a possibility if bearing failure. On the conventional seal is an arrow showing the direction of the crankshaft rotation as shown in Figure 1. This arrow (marked with white) should be visible form the rear of the engine when properly installed.

One way to verify that you are using the correct rear main seal is that the conventional seal is used on crankshafts that have a rear crankshaft seal area diameter of 2.3202 - 2.312. The rear main bearing seal has to be lubricated during installation. If the seal is to tight, no amount of special type lubricant will make it work properly. Rear main bearing seal fit has to be correct or a leaking rear main bearing seal and/or a possible rear main bearing problem can occur.

The AERA Technical Committee"

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Re: Rear main seal what works?

Post by willik43 » Mon May 09, 2022 11:29 pm

I used PAYEN (right on pic) on several engines - no problem so far.
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Re: Rear main seal what works?

Post by YLG80 » Tue May 10, 2022 4:05 am

What you need to know was extensively discussed here: viewtopic.php?f=4&t=324783&hilit=seal+yves
With drawings and special point of attention with the crankshaft.
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