Leaking near flywheel
 

I've noticed a few puddles of oil under my truck lately, and so I finally get under there to look around. This may be a really stupid question, but am I supposed to be able to see my flywheel like this? This *seems* like the origin of my oil leak.

I guess maybe it's leaking from the oil pan gasket or elsewhere and just blowing back to this spot but this just doesn't seem right to me.

https://lh3.googleusercontent.com/vS...Q=w976-h976-no

Re: Leaking near flywheel
 

What engine and trans do you have? that's usually covered up by an inspection cover.

Re: Leaking near flywheel
 

It is the L6 230 engine, and 3 speed manual trans. Assume it's the SM318 but I don't know how to confirm that. In any case, do you think this would cause a bunch of oil to leak out? Seems like it to me.

Re: Leaking near flywheel
 

I had a combo like that on my 65, but dont remember what was covered up or if some of the flywheel was exposed.

Re: Leaking near flywheel
 

It seems you are missing part of the inspection cover...I can try and get a picture when I am in the shop. Could be a pan gasket or rear engine seal leak.

Re: Leaking near flywheel
 

Try this....

Re: Leaking near flywheel
 

Thanks Nanook, got a part number by chance? Having trouble finding it for sale anywhere that fits my engine/trans.

Re: Leaking near flywheel
 

I don't think the cover is going to cure the leak. Most likley rear main seal, or pan gasket.

Re: Leaking near flywheel
 

Hi Praxiss. My truck was also missing this piece. 235 and 3 speed manual trans, so the cover looks a bit different on mine. I got the cover from a wrecking yard, but you could try Aspen Auto.

Re: Leaking near flywheel
 

You have either a leaking pan gasket or a rear main seal. The missing cover has nothing to do with the leak.

Re: Leaking near flywheel
 

Thanks for confirming, Captainfab, hotrodder. It sounds like in order to change the main seal I'd have to drop the oil pan so I might as well do both at the same time.

Re: Leaking near flywheel
 

Try to get a 1 piece felpro blueline pan gasket. They’re the bees knees compared to the old ones you have to piece together and join with silicone. They also come with little tabs that hold the gasket in place while you install the pan.

Re: Leaking near flywheel
 

https://www.summitracing.com/parts/FEL-OS34509T/
Best ones I have ever used.

Re: Leaking near flywheel
 

I used one on my 61 and loved it!

Re: Leaking near flywheel
 

Whoa! Backup!
Never assume anything!
First order of business is clean up the oil mess. Clean enough to eat off it. Clean enough to see where it’s actually leaking from. Start at the top and work down.
Most of that oil is likely from the valve cover. Somewhere high up and to the front of the motor.
I had a strange leak once on my old 283. Valve cover leaking at the front. Ran down to the pan, along the pan rail and showed up on the tranny shift rods.
So before you put a wrench to it or open your wallet real wide, do yourself a favour and find the source.

Re: Leaking near flywheel
 

Valve covers, timing cover, pan gasket....have some fun and do’em all with good gaskets. You won’t regret it, nice having a 60 year old truck that doesn’t leak.

Of course, it’s a lot more fun if it’s on an engine stand and you don’t have oil dripping in your eye as you put the pan on.:lol:

Re: Leaking near flywheel
 

Valve cover gasket is new and that area looks clean, but I agree cleaning everything is a good first step. Though I'm not entirely sure how to accomplish that with the engine still in the truck. I've read dollar store oven cleaner is good.

Re: Leaking near flywheel
 

To my knowledge, Fel Pro doesn't make the one piece reuseable pan gasket for the 230/250 I6 that the OP has.

Re: Leaking near flywheel
 

I didn't see any single piece oil pan gaskets, so I went w/ the multi piece from rockauto. Gonna try to get all that gunk cleaned off this weekend and see what I'm working with before dropping the pan.

Re: Leaking near flywheel
 

Thanks for the thread. Reminds me I have to do my oil pan/rear seal also. woo hoo.

Re: Leaking near flywheel
 

99% positive the rear main seal is leaking, not the pan gasket, seal probably hard as a rock on an original never rebuilt 50+ year old engine. Very difficult to change out with engine still in truck. There should be a rectangular cover plate in the open area. They are often left off or lost after a clutch job. This is what it looks like and may very well be correct for the 230 250 also https://www.ebay.com/itm/1956-62-CHE...JZGf1X&vxp=mtr

Re: Leaking near flywheel
 

My 250-6 is leaking also. Replaced once when I did oil pan. Now Pan doesn't leak, seal does.

Any hot tips on replacing seal?

Re: Leaking near flywheel
 

The rear main seal is leaking.

Re: Leaking near flywheel
 

With the help of some kerosene, some degreaser, and a power washer, I cleaned up the engine reasonably well, and then drove it around for a while. Most of the engine looks to be dry/leak free, but it looks like there is some fresh oil by the rear main seal.

I know there are a bunch of threads on this, but I see some conflicting info. On my 65 GMC 1000 w/ the L6 230, do I need to unbolt or loosen the engine, and jack it up in order to get the oil pan off? In my GMC Maintenance Manual, the procedure for changing the rear main seal does not include this step.

I'm not looking forward to dropping the pan. It looks like a PO used gorilla glue or some kind of slight expanding foam to seal the pan. The pan has also been dropped and sprayed blue, but the blue is peeling off and I can see the original red beneath it. So Ideally I'll completely remove the pan, clean it, spray red again, and button it back up.

Re: Leaking near flywheel
 

Well, rain in the forecast here for the next week or more, so not sure I'll get a chance to dive into this for a while. One of the drawbacks of not having a garage with enough space to work in.

Re: Leaking near flywheel
 

I have a garage and no space to pull in and work on my truck. When I was single, I had a garage with lots of space to work on my projects AND park my luxury car from Europe. Now I'm married and have enough room for my tools...on wheels (woodworking) and extra large 3 story tool cabinet setting up a temporary table between two body panel work stands from Eastwood and a 2003 Suburban we bought new to drive and two teenagers picking my pockets bare. I think the storage is moving more toward the door and and my workspace may be zero by 2020 and I'll be working in the backyard...LOL

Oh well.............at least i've got my '64 project in the driveway (under a cover or the city will cite me, believe that!?) and do housework/remodel jobs in the driveway on my temporary table. Better than sitting around all day watching the boob tube. Have a good day all........

And yes to the above advice. Check top to bottom, it MIGHT be or MOST LIKELY your rear main, but could be valve cover, oil sending unit, blowback so give it a wash with oven cleaner and a power washer and then keep an eye out for that nasty brown stuff and ATTACK.

Re: Leaking near flywheel
 

Got under there again between rain storms and it looks like I'm missing a few bolts to hold the oil pan on. Whatever the PO used to seal it seems to be holding it in place well enough.

Still wondering if anyone can confirm whether I'll be able to drop the pan straight away or if I need to loosen the motor mounts and jack up the engine. Maybe this is a dumb question, I just want to be prepared before diving into that.

Re: Leaking near flywheel
 

Can anyone answer definitively whether I'll need to loosen and jack my L6 230 engine up a few inches on order to get my oil pan off of my 65 GMC 1000?

My maintenance manual does not mention this step but others here have mentioned it.

Re: Leaking near flywheel
 

At the risk of being the annoying guy who bumps his question but no one is answering because they don't know the answer..... bump.

Re: Leaking near flywheel
 

I would say that since no one has answered that means no one has tried. If it were me I would probably pull the engine to do it. I hate having oil drip on my head while I work under an engine but I do it everyday so I might be a little biased. I think it would be easier to get everything lined up and make sure you aren’t going to create a bigger leak at the same time. And while you’re at it you could throw a rear main in to make sure it’s good for a while as well.

Re: Leaking near flywheel
 

Your answer is to get one of those rubber mats and park it under the truck. It works for mine LOL.

On your question though, from what I have been reading here over the last few years, I'd say yes you need to lift it some to get the pan off. Maybe lift it with a board and bottle jack under the pan and support it with a plank across the top of the engine? Let us know how it goes.

From a forum on the AMC 6 cylinders they talk about maybe loosening some of the mains caps a bit to be able to get the top half of the seal out. The rear cap of course would have to come off regardless to get the seal out of it.

Re: Leaking near flywheel
 

This would be surprising to me that no one has tried to drop the pan on a 230 with the engine in place, but you might be right. I don't really have the space to lift the engine out entirely, and the prospect of trying to jack it up is also not great, so maybe I just live with the oil leak for now. I just don't want to get half way through the project, realize I can't finish it, leaving the truck in an undriveable state.

Re: Leaking near flywheel
 

I have never done it with a I6, but with a small block you need to either lift the front of the engine, or you need to turn the crank so that the front counterweight is up. Then the pan can be dropped down and slid back.

Re: Leaking near flywheel
 

I guess I'll find out in a few weeks.

Any suggestions for anything else I should do while I have the pan dropped? Current project list is just to strip and repaint the oil pan (a P/O painted it blue), replace the pan gasket, and rear main seal.

Re: Leaking near flywheel
 

Okay, so I had to jack the engine to drop the pan. No biggie. Two of the bolts were broken off by a PO so I extracted those, feeling pretty good.

But I can't get the damn upper rear main seal out of the channel no matter what I try. The lower seal was RTV'ed into the channel, so I expect the same from the upper. I think this means I will need to drop the shaft. The seal is the neoprene style with the metal rod through it, and I was trying to tap it out with a hammer but kept slipping, and put a tiny knick into the shaft so decided I better quit while I'm ahead. Gently filed down the high spots from the knick.

Can anyone point me to a write-up of how to drop the shaft, or explain it? I have the GMC Maintenance Manual for my truck but so far can't find a section on this.

Re: Leaking near flywheel
 

Have you tried pushing on the seal as you rotate the crank?
Push on it with the eraser end of a pencil.

Re: Leaking near flywheel
 

Not yet, I can give that a try.

Re: Leaking near flywheel
 

No dice. It didn't budge. But take a look at this bearing surface. Reckon it needs to be replaced? I don't know much about this stuff, having never done it before, but I would guess so. And it makes me want to pull the engine and disassemble everything, which I've also never done.

https://lh3.googleusercontent.com/mQ...O=w500-h716-no

Re: Leaking near flywheel
 

Yes you need a rebuild.

Re: Leaking near flywheel
 

My wife is going to be thrilled.