Rear Main Seal Leak


Rusty Driver
Rusty Driver

Posts: 147

Joined: Thu Aug 08, 2019 8:14 am

Location: Rostraver, Pennsylvania

Post Tue Apr 06, 2021 8:09 am

Rear Main Seal Leak

Well,
I totally screwed something up... I cranked over our BD240 last night for the first time since rebuilding it. Didn't start it, removed the plugs and just cranked it with the starter to see if I am getting oil to the top end. After cranking it over a bit, I noticed a lot of oil pouring out of the bellhousing. I had a machine shop machine the block to accept a one piece rear main seal using instruction provided on this forum. The seal I put in was tight as Hell fitting into the block, so I can't imagine oil getting around it, but it is.... Also, I gooped up the flywheel bolts with sealant.
Here's something I am wondering though: The reason I wanted to make sure I was getting oil to the valvetrain is because while talking to some of you guys, as well as a mention in the manual, it seems that certain rocker arm rail supports are ported to allow oil flow. I did not see any ported while reassembling the head. There are three part number supports installed if I remember correctly, and I matched them to the parts book to make sure. There are the supports at each end, two supports that have a bushing in them, and two supports that do not have a bushing in them, so its somewhat idiot proof. But again, I saw no porting for oil. I am wondering if I missed something, because I cranked it a good bit but never did get oil to the head. Even though it was pouring out the back, I would still think that some oil would have made it to the top. I could be wrong though... Do you guys think its possible that I have an oil passage block at the valvetrain, and if so pressurized the crackcase enough to push the oil past the rear main seal?
Probably just wishful thinking at this point....
Any insight would be appreciated. I am literally sick about this...
Attachments
Leak.jpg

Golden Jubilee
Golden Jubilee

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Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Tue Apr 06, 2021 8:38 am

Re: Rear Main Seal Leak

The amount of oil and the fact the engine hasn't run, suggest that a plug was left out during re-assembly. either a pipe plug in a oil rifle drilling or a "core" plug in the back of the cam shaft. I don't think even a buggered rear main would leak like that when just spinning over on the starter.
Don't despair, Pull the engine and look. If necessary, spin the engine over with it out and see where the oil is coming from.
You will not be the 1st nor the last to have something like this happen.
After all the angst only thing to do is get on with locating the problem.

Rusty Driver
Rusty Driver

Posts: 147

Joined: Thu Aug 08, 2019 8:14 am

Location: Rostraver, Pennsylvania

Post Tue Apr 06, 2021 10:09 am

Re: Rear Main Seal Leak

That's a good point. It is dumping a ton of oil. I can't imagine me not seeing a missing plug but I obviously missed something.
I'm going to pull the gearbox and see if I can get the bellhousing out without pulling the engine. I'm going to do it this afternoon.
I'll let you know what I find.
Thanks!

Golden Jubilee
Golden Jubilee

Posts: 5170

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Tue Apr 06, 2021 10:43 am

Re: Rear Main Seal Leak

If it makes you feel any better, I can tell you of the time I stuffed a fully load 460 Ford into a van, only to get almost no oil pressure, the pick tube gasket had slipped out of position and was sucking air.
Or worse, the time I assembled a relief valve wrong on a 80' manlift. When I went to check the pressure, deadheaded the pump and dumped 55 gal of hyd oil on the ground in record time, spitting the pump section in two!
We all make mistakes, and you can sit around and kick yourself, or put you big boy pants on and get on with finding the problem and fixing it.

Rusty Driver
Rusty Driver

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Location: Ridgefield, Wa.

Post Tue Apr 06, 2021 11:57 am

Re: Rear Main Seal Leak

Sorry to hear about your dilemma Bryon. I agree with Cornbinder. There is a 3/8'' pipe plug on each end of the oil galley. Wouldn't be the first time they were forgotten. It may be hidden now behind the bellhousing, can't remember for sure.
Like Cornbinder said there is also a 2'' expansion plug at the back end of the cam shaft.
Let us know what you find. Good luck
Dennis
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Golden Jubilee
Golden Jubilee

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Joined: Sat Dec 01, 2012 9:55 am

Post Tue Apr 06, 2021 2:02 pm

Re: Rear Main Seal Leak

I have also seen the caution about one of the head bolts being drilled for an oil passage to the rockers. Not the case on the SD's or BD's however. As much oil as was spilling out the back, you might not have gotten enough pressure in the system to get oil to the top of the engine.

Rusty Driver
Rusty Driver

Posts: 147

Joined: Thu Aug 08, 2019 8:14 am

Location: Rostraver, Pennsylvania

Post Fri Apr 09, 2021 8:33 am

Re: Rear Main Seal Leak

Well I found the culprit and you guys are right. The 3/8 pipe thread plug in the main oil passage was left out. The machinist must have removed it when cleaning the block. He put new freeze plugs in but apparently forgot about this one. I can't believe I didn't notice it.... I am assuming I though it was a bolt hole or something. I have attached a photo.
I got everything put back together yesterday, with the exception of the transmission. I'll put that in tonight.
Regarding my concern about oil getting to the top end, I cranked the hell out of the engine and eventually oil started dripping out of the rocker arm rail, so it seems to be getting oil.
Thanks again for all the help. It sucks I had to pull everything apart, but I guess it could have been worse.....
Attachments
Plug.jpg

Golden Jubilee
Golden Jubilee

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Location: Minnesota

Post Fri Apr 09, 2021 11:59 am

Re: Rear Main Seal Leak

Good Bryon,

Rusty Driver
Rusty Driver

Posts: 119

Joined: Wed Jul 15, 2015 9:04 pm

Location: Ridgefield, Wa.

Post Fri Apr 09, 2021 12:49 pm

Re: Rear Main Seal Leak

Guess you found the leak Bryon. Good job. I would think that would have been a pain with engine in the truck.
Dennis

Golden Jubilee
Golden Jubilee

Posts: 5170

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Fri Apr 09, 2021 1:12 pm

Re: Rear Main Seal Leak

Glad it was simple, often it is. It would have been worse if it was dumping oil internally, like into the timing cover, and the only indication would be lack of oil pressure. Those can leave you tearing your hair out and second guessing all that you have done.
BTW, I think most people "over think" the oiling on start up. I lube everything with a film of oil as I assemble it, if the engine in question has an external oil pump, I dump a 1/2 pt or so into it before installing, turning it to spread the lube around, if internal to the oil pan, I just fill the sump before firing.
Once it starts, I look for oil pressure and oil making it to the rockers.
I've built some fairly pricy engines (Cummins K-19 liter) and never had any problems.
I once had a Cummins 885 sit in my barn drained for over 15 years and there was still oil dripping off the crank bearings when I pulled the caps.
As long as you don't assemble dry, you can idle an engine for a long time and do no damage on just the lube you assembled it with. Don't rev it when you start, just let it idle and look for oil pressure.
Because there are a few engines out there that have the drive gear on the bottom of the dist, so with the distributor out, you can spin the oil pump shaft, people think you need to do that, you don't.
I much prefer the drive gear on the oil pump shaft and the dist to be driven off the top of the oil pump, that way the most important drive is the one that has the gear, much less damage if the dist stops turning before the oil pump than the other way around.
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