Help, Another Oil Pan Leak Thread

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blewbyoutobad

blewbyoutobad

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OK FABO, I need some help. I have a stock block 340 with an 8 qt Milodon oil pan. This is a new motor with only 200 miles and I have had the pan off 4 times trying to fix the rear pan seal from leaking. I have installed the pan with and without gaskets (RTV only once) to see if I could get a little more clamping force on the gasket. It leaks between the main cap and rubber seal. The last time I staged all the gaskets on the pan with RTV including the rear seal and bolted it to an extra short block I have to seat them. Looked excellent when I removed it. I installed it on my motor, no RTV on rear seal at main cap and it started seeping after 5 minutes of running. Do I scrap all the gaskets and just use RTV. The front timing cover gasket has never leaked. Any ideas appreciated. :BangHead:
 
Are you sure it is not coming from the back of the block up higher? Or the center of the crank register. Have you ran this assembly before or is this a all new engine to you?
 
This is all new . I can see the seepage at the rear seal coming down the Lakewood BH. There is no oil inside the BH. When I pulled the pan you could see the oil between the seal and main cap.how do you seal this area.
 
I've never had that much trouble getting a pan to seal there. I use RTV on the pan and the seal. Have you used a different main seal yet? Make sure the lip on the seal haves are facing forward.
 
Some Aftermarket pans are cheap Chinese crap. Had that problem with a chrome Chevy smallblock pan.
 
Mike69cuda said:
Some Aftermarket pans are cheap Chinese crap. Had that problem with a chrome Chevy smallblock pan.
Click to expand...


Agree totally!. try putting the pan on a smooth flat surface like a tabletop and see if it sits flat or rocks back and forth. Could be a warped pan. Just because it is made by a big name manufacturer ( Milodon) doesn't mean it couldn't be defective!!
 
Never had an issue there. Any chance the pan is bottoming out on the oil pump or something stupid like that?
 
Moper
I did find the Melling HV pump hitting the pan. Clearanced it last time but didnt help. You are on to something. I think its time to get the clay out.
 
Have you checked the depth of the bolt holes for obstructions? Are the pan bolts clamping all the way?
 
Had almost the same problem with a 383 I built. Oil dripping from the rear pan bolts and off the bottom of bellhousing. No oil inside bellhousing... removed and sealed oil pan 3 times and was still leaking. Finally put UV dye in the oil and found it coming from the rear main seal. Could see a drop on the top of the seal retainer, was running the retainer and spreading from there. Again never had oil inside the bellhousing ...... dropped the pan again and replaced the seal, been good ever since ..... honestly it's kinda hard to mess up an oil pan gasket, I think I'd look elsewhere.
 
Since this has been off and on a lot, make sure the areas around the bolts are flat, and level with the rest of the pan's gasket surface. If you have put significant torque on the bolts trying to get things to seal, then these areas may well be distorted, and that will disrupt the sealing pressure in some areas. It should not take much bolt torque at all to get things to seal well.

I always use a skim coat only of RTV on the side gaskets and a modest bead of RTV around the end seal. RTV goes on both sides of all gaskets, with a blob in the 4 corners where the sides meet the end. Use Black RTV and let it set up overnight.

Also, were the small 'sprues' in the rear main seal that go in the slots under the rear cap in place when the rear seal was installed? These come in couple of configurations.
 
I've always install the gskts dry, or if under-car, use "gorilla snot" contact cement to secure the side gskts, so they can't slip.
I believe with clean, true mating surfaces, let the gasket do it's job, as it's done for decades, without "sealers".
Only RTV I use is 4 pea sized dabs where the gaskets meet.
Never tried all the goops, cuz never had a leak in any of the dozens of engines, all breeds.

I've often found RTV to be more a problem than cure, cuz if you try "snugging" bolts on dried RTV, and break it's adhesion to either surfaces, the RTV will squeeze out, and there's your leak.
Good luck

P.S. there are many, many similar threads if you do a "search". One very recent.
 
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I had that exact problem after I had my block line honed.
It had run well in the first season; but I had figured out that the decks had been machined ridiculously off square both side to side and end to end. So winter came and out popped the engine
Turns out that after the line-hone, the factory 360 seal was no longer even touching the crank on one side, while the other side was smooshed onto the crank. I saw that after I replaced it, chalking it up to a faulty install on my part, and sure enough the second seal leaked almost right away. That's when I went back to have a better look at the removed seal,and thought about it. I went straight back to the machine shop, which denied culpability.
But said the manager, if I brought them another block they would line-hone it for free. Yippee!
What about the boring,honing, and decking. I mean the whole reason it's here is cuz you said the bores were crooked. and I brought it to you cuz I knew the decks were not square and you said you couldn't square it until you line-honed it.
Well no that would be extra, cuz that part of the job was done right.
Wait what? you want me to pay for your mistake, and I should still supply another block for you to practice on. I don't think so.
Well that's the best I can do, said he.
Best daymn machine shop in townmyazz, muttered I.

So I took my leaker home and stuffed a rope seal in there, and the fix would have to be good-enough for me. It still seeps a bit. That was 2004.

Not saying this is your problem, but inspect your previously-installed seals for the tell tales. I guess also make sure they were not installed backwards,lol.
 
Went out tonight and worked on pan problem. I used some clay and clearanced the oil pump and the pump pickup. No problems anywhere. I torqued it down all the way around. I do need to work some high spots on a few bolts holes after having it on and off so many times. I just hope I am not chasing a ghost with a rear main seal leak that appears to be the oil pan. When I pulled the pan yesterday there was oil on the inside of the seal where it presses against the main cap. That tells me no rear main seal problem, I think. Thanks guys for all your comments and help. I also bought some right stuff today and will probably use it on the rubber seals inside and outside. I have never had a leak on the rails or the timing cover. :BangHead:
 
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