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1940 buick special rear main seal replacement.


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Anyone ever have any luck on changing a rear main seal on a 1940 buick special with crank in place ? I been looking at a tool called a sneaky pete. Any luck with using one of those ? Also thinking about going to a rubber seal vs the rope seal. 

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I just completed work on my '40 engine, but it was out of the car.  Even with the crank removed, getting the seal out of the block was a real chore.  I can't imagine what it would take if the crank was still in the block. If you were to consider removing or loosening the crank, I think you are going to have access problems with the front cap.  The crank weigh nearly 100 pounds and dealing with the weight while you are under the car could present yet another challenge.

 

I get your point about doing the replacement with the engine in the car though.  Pulling the front end sheet metal risks damage to the paint and is a multi-man effort.  No one responded with an encouraging word, I hate that all I can offer is doubtful encouragement.  

 

 

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Dan,  Willie  [old tank] Pittman has a seal replacement guide on his site. I don't know how to  attach a link.  He is on here a lot. He actually uses, I think, a piano wire inserted  fraction at a time over the top part of the seal. You may have to see his pictures to understandl

 

  Ben  

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Thanks for the tips everyone.. Guess the only true way of finding out is to get in there and pull the main cap and go to town on it. Never even had this engine fired up yet. Just figured while I have the pan off would be a good idea to replace the seal. Dont look like this motor has been messed with in 50 years ! The oil in it looked like thick mud. But motor turns over good. Will do compression test once I prime the engine. Sat so long cam and everything looks dry. Don't want to risk hurting the bearings. 

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I don't think I would touch the rear main unless everything else checks out OK.  If I were to change the rear main, a lip seal would be the better way to go.    

   The time to pull the pan again.  10-15 min.   time to change rear main.  HOURS, with lots of profanity.

 

Bill

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Right. I can see where you guys are coming from. And I get your point about it being a hard job. I was just thinking it would be a good idea to replace it. I know sitting for long periods of time like this isn't good on seals or motor. And everything on this motor appears to be untouched and original. Not sure if it leaks are not. But the oil pan and dust cover around that area is very greasy. But that could be from anything. I do plan on replacing any gaskets I can get my hands on. That way I know motor will be good to go. As long as the rings and valves are good think I will be fine.. I did feel around on all the rods. Everything feels good and tight like it should. And all the clearance's seem to be ok. Also turned motor over by hand with valve cover off. All the rockers have good movement as well. I'm thinking this baby should run if it holds good compression. Finger's crossed ! Lol I just want to do everything right the first time while Im in there. But I'm sure you guys know more about these engines than me. My first time working on a old buick 8. So if it is that rough I think I'm going to just take your guys advice and put the pan back on and hope for the best.. Thanks again for all your help. Let you know how it goes when I fire her up. 

Edited by Dan283 (see edit history)
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46 minutes ago, Dan283 said:

 I did feel around on all the rods. Everything feels good and tight like it should. And all the clearance's seem to be ok.

 

While the pan is off, consider plasti-gaging the rod and crank journals.  

 

To check for old rear seal leaks, since you have not run the engine, pull the flywheel cover off.  If it has a good layer of dried oil, particularly at the drain hole in the bottom, you know it has been a leaker.  

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On 1/17/2018 at 9:01 PM, kgreen said:

 

While the pan is off, consider plasti-gaging the rod and crank journals.  

 

To check for old rear seal leaks, since you have not run the engine, pull the flywheel cover off.  If it has a good layer of dried oil, particularly at the drain hole in the bottom, you know it has been a leaker.  

Pulled it off. Looks pretty dirty ! Good tip on using plastigage.. It did cross my mind to do so.. The rod side clearence's did seem ok. And like I said i did pull up and down on rods. They all feel good. But I know that dont mean the bearings are ok. Hoping the clearence's are good and it holds good oil pressure. Probably will just leave the bottom end alone if I can help it. Might rebuild oil pump and just bite the bullet and fight with rear main seal. If I get it in ok. But for some reason when I start this thing up and motor isn't right. It will be coming out and getting rebuilt. Really hoping to avoid that if possible. Money is very tight right now.. Want to get car mechanically sound. Leave the patina and clear coat over it. Think it looks pretty cool just the way it is. Will leave it 100% stock. Not doing any mods on this one. 

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With the pan off, you definitely should check the oil pump gear clearance. Costs nothing and it is cheap insurance. Spec is .0005" to .004"

Also clean out the oil bypass valve to be sure it is free and clean and the spring is OK.

Also, open up the oil screen assembly, they are often really dirty inside where you cant get at everything.

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Thanks everyone for all the help ! Very great tips ...I got the old buick running finally ! After cranking for few seconds it fired right up! Motor sits and idles like a new one. Really surprised me how well it runs after sitting for years. Not sure how long it takes for oil to turn into thick mud looking stuff. But my guess would be a long time. I ended up leaving rear main seal alone. Looked under car no signs of any leaks yet. The only thing I did to motor was take pan off and clean everything good. Put pan back on with new gasket and oil. Didn't even mess with old wires are plugs. Very pleased with how well engine sounds ! 

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  • 2 weeks later...
On 1/28/2018 at 10:47 PM, Morgan Wright said:

If it ain't broke, fix it 'till it is.

Not the case here Morgan. Haha think I made the right call by leaving it alone. I know the seal is almost 80 years old so figured be a wise idea to replace while pan was off. But I'm just going to run it till it needs something. 

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  • 2 years later...

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