Seeking Tips/Tricks for Replacing Rear Main Oil Seal

[Stargrinder]

Folks, 

I have been searching the forum for some tips on how to replace the rear main oil seal on a flathead v6 without having to remove the motor or transmission.  Is there a way to do so or do just by dropping the oil pan or do I need to have the trans pulled?  Any info would be great.

 

I saw a couple nuggets here that make me believe it is not possible.

 

Thoughts?

 

Thanks.

[Ulu]

It depends on if the engine has a one-piece or two-piece seal. You can't get the 1-piece out.

But if you don't know which one you have you pretty much have to pull it apart.

[keithb7]

What model/year car do you have. What tranny?
 

Recently I tore down a 1938 201 engine on an engine stand. It had a 2 pc rear seal. There are 3 small bolts that hold each seal half, in place. They are located between the flywheel and the engine block. Specifically, between the crank mounting flange for the flywheel,  and the block.  The upper seal half mounting bolts are difficult to access. 

Removing tranny and clutch will gain access to flywheel mount bolts. For some reason I recall the  flywheel will be stuck up inside the bell housing and not come out the bottom? Perhaps it can somehow be propped out of the way to access the seal bolts? The flywheel housing is not overly easy to remove either, with the engine installed in the car. I suspect it can be done but I’d be inclined to think it’s a fairly time consuming (aka frustrating) job. I tend to think that pulling the engine seems like a better option if you have tools and space.

 

While the engine is out lap the valves too! Roll in all new main & rod bearings. Slide pistons/rods out, hone cylinders and re-ring it. See this is what gets me in trouble and why I have not done this yet. 
 

This video shows my findings. 
https://youtu.be/cIzZAhkxJIU

 

That’s my perception. Fine folks with more experience will reply shortly. 

Edited March 14, 2020 by keithb7

[keithb7]

Some perspective:

 

 

[Sniper]

My 218 has a leak somewhere in the front, it appears to me the timing cover seal.  For all of Chrysler's alleged engineering brilliance they fail in the same way most engineers do, no thought to designing for maintenance.

 

I plan to yank the entire engine out, clean, reseal and paint it. 

 

I may as well do the valves and look at the bores to see if they need attention.  Valve adjustment won't ever be easier than with the engine out.  Probably draw file the block surface and put a new head gasket on it along with my Edgy head.

 

That seems the most effective way to fix leaks on this engine. 

 

 

 

 

 

 

 

 

[Stargrinder]

Keith,

I have a 1950 Coronet.  Should be a two piece seal.  I am trying to avoid pulling the engine simply because I lack the experience and equipment to do the job.

 

The video you provided was extremely helpful.  I think I might try to live with the oil leak for now ... or try to find a shop that can do the job without emptying my wallet.

[Andydodge]

I replaced the rear main seal on the 41 Plymouth Coupe I had, it was supposed to be a rope seal and as the Best brand gasket set I had only had the 2 different neoprene seals and side gaskets I ordered a rope set.......once obtained I dropped the sump and found that there was a neoprene seal but NO SIDE GASKETS OR SEALS........lol........I replaced only the lower portion of the 2 piece seal but more importantly installed the correct shaped side gasket seals and with a new sump gasket the oil loss virtually stopped............as for doing the job yourself the main thing is ........are you able to safely lift the car up, safely support it on jackstands, do you have the tools to drain the oil, drop the sump, clean it out completely, remove and install a new sump gasket..........then drop the rear main cap and replace/remove whatever seal is there........if its shown that you have a one piece or buggered two piece or rope seal then you have to decide what your next step is........I was lucky in that the main cause of the leak was that the previous owner or some fool had not installed any of the two required side seals or gaskets and there was a gap when the rear main was attached of 20-30 thou....enough for a regular pissing of oil.......lol...........so installing these fixed the worst of it............dunno if this helps or confuses the issue.......Andy Douglas    

[Stargrinder]

Andy,

Actually that helps.  I will put it on some jack stands in the next couple week and see how things look.  Maybe I will luck out.  In the interim I added some ATP AT-205 re-seal to the crank case.  It actually slowed down my leak.  I need to drive the car a bit more to see if any of the rubber seals in the crank case get revitalized.  That was my last resort before breaking out the tools or taking it to a shop to have the trans removed and the upper/lower portions of the seal replaced.