Rear main seal leaking.

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Badart

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This motor hates me. My 318 has had a leaking rear main seal since rebuilding it and it seems to be getting worse. I know that it is the rear main because of all of the oil on my flex plate and convertor. At first it was just annoying and I thought that I could deal with it, but now it's starting to piss me off.

My plans are to pull the motor and fix it. My question is that I want to know is there any way of changing it without pulling the heads and pistons? I am thinking that If I pull the timing cover and remove the main caps I can lift the crank enough to change it. What do you think? Anyone ever try this. I don't want to spring for new head gaskets and take a chance with one of them leaking later or tear down the entire engine.
 
I've done it by just dropping the pan and rear cap. I think I had to loosen the other caps to release the tension on the top half of the seal. Not sure if this is the correct way but it worked for me.
 
you can actually replace it with the crank in place and even the engine in place if you can get the pan off and don't mind working upside down! If you pull the engine, once it is on your stand and upside down, pull the pan off, pull the rear main cap, and you should be able to turn the crank and work the seal out. Work the new one in, put a bit of silicone on the ends of the 2 pieces and put the rear main cap back on. Pan back on, and you should be good to go.
 
63dartman said:
I've done it by just dropping the pan and rear cap. I think I had to loosen the other caps to release the tension on the top half of the seal. Not sure if this is the correct way but it worked for me.
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That is good news. Were you just able to push out the top half with the crank installed? When you reinstalled it did you install it did you install it so the seal would overlap the main cap? I hope you know what I mean.
 
Yes and Yes. I was able to push the top half out relatively easy (I don't think there was any rtv or sealant on the old one)and I also turned it to overlap the gaps. You have to be careful though because the top half can easily be damaged by the sharp edges of the metal. I had to buy two because I shaved off half the top seal trying to install the first one.
 
63dartman said:
Yes and Yes. I was able to push the top half out relatively easy (I don't think there was any rtv or sealant on the old one)and I also turned it to overlap the gaps. You have to be careful though because the top half can easily be damaged by the sharp edges of the metal. I had to buy two because I shaved off half the top seal trying to install the first one.
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Sounds good. I must have damaged it some how when I installed it the first time. Thanks.
 
Badart said:
Sounds good. I must have damaged it some how when I installed it the first time. Thanks.
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First off I'm new at building engines.

My machine shop pointed out to me when I brought my block in for work that I had installed my new main seals backwards! I was a little embarressed but now I know to check the orientation of the seal design.

Possibly you may have put yours in backwards like me if it leaked from the start. Trying not to be a smart a.. but you might want to look closely at this facet of your build.

Good luck.
 
I thought I had a rear main leak one time and after further investigation it was the Oil Pressure line by the distributor that goes to the guage. I tightened up the fitting and it fixed the problem....Just something to check on is all!
 
do it in the car.

remove pan, rear main, push seal around and out with a small pick.

stick the half in offset so one side is recessed and the other sticks out, put a lil dab of rtv on the ends that touch each other and stick it together.

MOST IMPORTANT IS A LIGHT COAT OF OIL TO THE SEAL FACE THAT RIDES AGAINST THE CRANK. or else you'll burn it up and leak again.
 
Nice catch Bad...lol. I hate to admit it but I've put 1/2 of the lip seal version in backwards before... I use rope for most builds now.
 
Badart said:
This motor hates me. My 318 has had a leaking rear main seal since rebuilding it and it seems to be getting worse. I know that it is the rear main because of all of the oil on my flex plate and convertor. At first it was just annoying and I thought that I could deal with it, but now it's starting to piss me off.

My plans are to pull the motor and fix it. My question is that I want to know is there any way of changing it without pulling the heads and pistons? I am thinking that If I pull the timing cover and remove the main caps I can lift the crank enough to change it. What do you think? Anyone ever try this. I don't want to spring for new head gaskets and take a chance with one of them leaking later or tear down the entire engine.
Click to expand...

Before you tear it down- make sure it is not the oil pressure sending unit that is leaking- You can probably figure out how I learned this the....... Just thought would mention it.....
 
Mad Dart said:
I thought I had a rear main leak one time and after further investigation it was the Oil Pressure line by the distributor that goes to the guage. I tightened up the fitting and it fixed the problem....Just something to check on is all!
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Lol. I had a small leak there too, but I have already fixed it Mad Dart.
 
Badart said:
Lol. I had a small leak there too, but I have already fixed it Mad Dart.
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Would have been nice if it was the only leak!

Change the seal out in the car like Justin "1wild&crazyguy" is telling you. I have done that before. PITA to get the pan off and clean for a good seal, but the seal replacement is a piece of cake!
 
If you don't put a thin film of RTV on the surface between the block and rear main cap it will leak. I have changed one in the car before successfully. The rubber seal on the top, just push on one side, it will move, then grab the other side with some needle nose.
 
340sFastback said:
If you don't put a thin film of RTV on the surface between the block and rear main cap it will leak. I have changed one in the car before successfully. The rubber seal on the top, just push on one side, it will move, then grab the other side with some needle nose.
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I actually found some shop manual instructions that said to do the same thing with joint compound between the block and main cap. I changed it out today and I have to tell you that I would rather be kicked hard in the junk than do it again. The hookers were the biggest PITA, because I had to pull the valve cover to have good access to the drivers side header bolts and unbolt the headers. At least my header gaskets were fairly new and didn't come apart so I will try and reuse them. I just hope that I don't have any leaks from my oil pan now. LOL Thanks for all of the help.
 
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