Rear main seal
 

Hi everyone. I have a 69 C10 longbed that i bought with a rebuilt 350 smallblock. I noticed alot of leaks so i took it to a shop and got an estimate and they said it was the rear main, the transmission gasket, valve cover gaskets, speedometer connection on the tranny and a seal on the side of the tranny, and it would be $1500. So i replaced the valve cover gaskets and i had a friend do everything else for $600. I got the truck back and it was still leaking. My friend said it was the oil pan cause it was old and warped. So i ordered a new oil pan and fel pro gasket and put it on myself in the driveway which was very challenging and topped off oil on dipstick and looked under truck.......STILL LEAKING!! So i took it to a local shop yesterday and asked the guy to find out what was going on. I called him a few minutes ago and he said its definately coming from the REAR MAIN SEAL. I said i just had it changed and he said if i just had it changed then there may be something wrong with the motor. Im really frustrated and dont really know where to go from here. So i have some questions..........if its coming from the rear main seal and i just had it changed, what else could it be?? Did my friend maybe put it on wrong?? Is there something else behind the rear main seal that can go bad and cause the rear main to leak even though its new? Im kinda at my witts end.....any help would be very appreciated.

Re: Rear main seal
 

I had my friends do work on my truck .. That I wasn't able to do my self .. After throwing money at them to " fix it " I said F it and took it to a shop .. So if anything goes wrong it's under the warranty .. It's always nice to try and save money when you can but at times it's better to just pay .. I'm getting my truck overhauled right now from the rear end to the motor for 1700 .. And Iv payed people to " fix " already . Some times it's better just to pay the extra for it been done right the 1st time

Re: Rear main seal
 

it could be several things, some rear mains had a rope seal, and some had a rubber seal, the rubber seal can be installed backwards and will leak, the rope seal could have some crud left in the hole or around the crank . the seal could have been damaged while installing it, and the pan gaskets are hard to get to seal some times, just check and see what went wrong and go from there...and good luck.

Re: Rear main seal
 

Yeah im at the point to where im not really concerned to much about the price as long as it stops leaking.

Re: Rear main seal
 

When did a small block Chevy have a rope seal? News to me...

Re: Rear main seal
 

Yeah im at a point where i just want it fixed and price isnt really a concern in exchange for peace of mind

Re: Rear main seal
 

My rear main seal was a two piece seal. So if its still leaking from the rear main seal it cant be anything else but the seal?? Im asking cause im just hoping he put it on wrong and its not anything else

Re: Rear main seal
 

it could be that the sealing surface on the crank is worn, but the seal could have been damaged also. only way to know is take a look.

Grip : rope seals were made before 2 piece rubber seals came out , the over haul gasket sets came with both ...it was up to you witch one you wanted to use. hope this helps.

Re: Rear main seal
 

Clean off the back of the motor from the top down and then look for leaks. Clean it absolutely spotless then use some white cotton gloves to feel around behind the intake and heads.
Could be leaking from the rear seal on the intake, the distributor seal or the oil pressure sending unit.
Rear main seals don't generally leak sitting in the driveway. You need some rpm and crankcase pressure to make them leak.

Re: Rear main seal
 

While it's true they won't leak in the drive without the engine running, drips that gather on the pan will fall in the drive. The clean and find the leak advice is sound. Find where it leaks from THEN fix that. Repeat as needed. Or in the case of some early SBCs repeat ad nauseum.

Find the leak. Look for damaged parts. Replace damaged parts, gaskets and seals.

Re: Rear main seal
 

Yeah i finished putting oil pan on and added about four quarts of oil and left it sitting in the driveway while i left to run some errands and came back and the only leak was from the drain bolt on bottom of the pan. So i tightened it and it stopped. Then i started it and backed it into the street so i could fill it on level ground. It was running in park and as i walked up the driveway to get the rest of the oil i noticed oil coming from the front and the back of the pan. So i was frustrated at that point so i toik it to a shop and talked to the owner of the shop last night to see what he found and he said its definately the rear main seal and the timing chain cover. I said that i just had someone change the rear main seal and he said if someone has already changed the rear main seal and its still leaking then there is probably something wrong with the motor and if he tries to do the seal again, he cant guarantee it cause someone already did it first and it leaked.

Re: Rear main seal
 

So hes saying that its the rear main seal. So if it is the rear main seal and its done correctly it shouldnt be leaking right? Its either its done right or its not?? It cant be anything else if its leaking from the seal right? I mean if hes saying its the rear main seal then thats what it should be and that means that my friend i payed to change it in his driveway didnt do it right?? And if hes saying that its a problem with the motor ,what other problem could it be?? Isnt a bad rear main seal exactly what is is?? A bad rear main? Or is there something else in that area or around the seal that could cause a new seal to leak? Im just really frustrated and this forum has been my outlet. All the feedback has been great and i really appreciate all the help.

Re: Rear main seal
 

Do you have the convertor dust shield in place?
Any oil dripping out of the weep hole in the bottom of it?
When you put the new pan gasket on did you put the end seals on the pan or on the block?
Did you use a one piece pan gasket?

Re: Rear main seal
 

Seals can be easily damaged during install or installed improperly. I would bet that's all it is. Have your friend buy you some beer when its all said and done. If something is damaging the seal after installation, it could be a bottom end problem but I wouldn't bet on that being the case.

Re: Rear main seal
 

I didnt install a converter dust shield. And i installed a new bm holeshot converter while rear main was being replaced. And i used a fel- pro one piece gasket on oil pan.

Re: Rear main seal
 

I'm sure you've seen this thread Did you install a nylon or copper gasket on the oil drain plug too? For years I used the same one after each oil change. Now I use either copper or nylon washers on the drain. I got tired of seeing them back themselves out just enough to drip.

Re: Rear main seal
 

Ok so most likely installed wrong or damaged during installation. I wasnt there when my friend installed the main seal but the times i went over to see how things were going he seemed like he was getting frustated and impatient with the work. Struggling and swearing. So maybe he tried to force things. Well im going to get the quote from the shop my truck is at and take it somewhere else for the repairs. Cause the shop that my truck is at has a bunch of new porches and mercedes, and it seems like the owner is a little more concerned with thoses cars. And my truck is an old school headache to him.

Re: Rear main seal
 

Seems like these fix by a friend in the driveway hardly ever turn out good. The rear main seals can be easily damaged during install, I also think this is what happened. I also think you have an oil pan sealing issue, which will likely be taken care of when you have the rear main fixed by a professional.

Re: Rear main seal
 

keep us posted on the new fix, and good luck....oil leaks can be a pain in the .....

Re: Rear main seal
 

This is a common problem , most older small block chevys leak , the rear main is notorious , the seal can be installed backwards and cause a leak , where the 2 halfs of the seal meet should be offset 3/8 of an inch from the edge of the block [per felpro] , a good working pcv valve will help prevent and in some cases [few] cure leaks , other areas in the back of the engine that commonly leak are , oil sender , where the intake and block come together , distributor seal , valve covers .

Generally when the rear main is the culprit it slings oil onto the flexplate or flywheel
I along with most others on this board im sure "FEEL YOUR PAIN'

Re: Rear main seal
 

Through '58 all Small Blocks have a rope seal. '59-'86 have a neoprene seal. '87 up have a 1-piece seal that is much better about not leaking.

Re: Rear main seal
 

X2, if you rebuilt your own motors before crate engines. The rear main seal in a SBC was always a PIA. You would cross your fingers when breaking in the motor. The lift that my G-Pa had in his barn was a blessing. The 3/8 offset method was what we always went with. Even then it wasn't a 100% success.