Rear Main Seal leak - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 10-08-2006, 10:31 PM   #1
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Default Rear Main Seal leak

So I went into the mechanic shop on friday...


Well I knew my rear main was leaking, as i've seen some places and my friend did some research, I was under the understanding that replacing it might or might not fix it, seeing as the crankshaft might be out of balance causing it to leak. I got the work done cheap since the dealer paid half as this car was just sold to me, I just got it home 2 days ago and well, it leaks still.

Here'* the questions to anyone who is knowledgeable..

1. My father informed me that in his opinion, the rear seal might still be "settling in" is this possibly true and does this mean the leak might go away or get smaller?
2. Since I got the car with thicker oil and additives I BELIEVE that kept this leak from occuring (it only started after I changed oil) I have put CD2 oil stop leak in, after about a hundred miles I think I am noticing a slight bit less of a leak, has anyone else used this or similar products? Is it a smart idea? What other suggestions are there.

Please do note, I don't have a "load" of money, my car is in otherwise mint shape, and I have to keep this baby running for at least a year, using it in an average miles per year way. If anyone has ANY suggestions, please let me know!

Thanks to everyone in advance,
Michael (ChilinMichael)

1995 Bonneville SLE 3.8 Series 2
Green with dark tan interior
Performance audio, sunroof, etc etc (Including those lovely gold wheels! lol)
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Old 10-09-2006, 01:37 AM   #2
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I hear a little Dodge will fix that up....



(Inside Joke rofl)
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Old 10-09-2006, 02:05 AM   #3
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Default Re: Rear Main Seal leak

Quote:
Originally Posted by ChilinMichael
I was under the understanding that replacing it might or might not fix it, seeing as the crankshaft might be out of balance causing it to leak. I got the work done cheap since the dealer paid half as this car was just sold to me, I just got it home 2 days ago and well, it leaks still.

Here'* the questions to anyone who is knowledgeable..

1. My father informed me that in his opinion, the rear seal might still be "settling in" is this possibly true and does this mean the leak might go away or get smaller?
2. Since I got the car with thicker oil and additives I BELIEVE that kept this leak from occuring (it only started after I changed oil) I have put CD2 oil stop leak in, after about a hundred miles I think I am noticing a slight bit less of a leak, has anyone else used this or similar products? Is it a smart idea? What other suggestions are there.

Please do note, I don't have a "load" of money, my car is in otherwise mint shape, and I have to keep this baby running for at least a year, using it in an average miles per year way. If anyone has ANY suggestions, please let me know!
Did they pull the engine and/or the transmission out of the car? That is the only way to get to the rear crankshaft seal. It is driven into an aluminum carrier that is bolted on to the end of the block and is covered by the flex plate (flywheel). The seal is a flexible neoprene lip seal with a garter spring to hold the lip against the crankshaft. If the crank is badly worn, a sleeve can be installed to provide a new sealing surface. If your crank is so badly out of balance that a new lip seal will not retain the oil, you have a lot bigger problems than the crank seal. Not saying it is not possilbe, but I have never heard of such a thing. I wonder if the leak was at the lip seal or where the seal carrier mates to the oil pan sealing surface. In that case, they may have just dropped the pan and gooped the surfaces with silicone RTV. Do you know exactly what was done?

You CAN do this work yourself, but it ain't easy. I would opt for dropping the trans, leaving the engine in place, then removing the flywheel and seal carrier and installing the new seal. The parts cost for this work is really small, like less than $20. If you have a lot of time, and can rent an engine hanger for dropping the trans, you can get it done yourself in two or three days. If you have to pay for the labor, it will cost you a bunch of $$$.

What usually happens to the lip seal is that it gets brittle and develops a radial crack. If that is your problem, the leak will be pretty fast. You could lose a cup of oil sitting at idle in less than 20 minutes, for example. And there really is no other fix than to replace the lip seal. But even if your problem is that the seal has just worn so that it no longer seals, it will not get better. Additives in stop leak products are OK for a $200 car that will go to the scrapyard before being repaired, but I would not use them in a "keeper." They will soften and swell the rubber in all the engine seals, not just the one you want to soften. This may help some seals and harm others.

Your Dad may have been referring to the older style rear main bearing seals that were made of packing and that would "wear in" over time. That ain't what you got.
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Old 10-09-2006, 07:32 PM   #4
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A faulty PCV valve can allow pressure to build in the crankcase forcing oil to leak out. Not very likely but should be checked.
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Old 10-09-2006, 09:19 PM   #5
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Well I went to the shop today, the flywheel is bone dry and they say it'* not the rear main...

Now another leak cropped up, my oil pan gasket.
Also seems i have some seepage around the lower intake manifold.

I feel so bad considering the rest of the car, is mint
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Old 10-10-2006, 12:01 AM   #6
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when cars sit for long periods of time the gaskets wear out.



the oil pan is not a bad job if you are changing your oil anyway. just getting all the torque right is the hard part
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Old 10-10-2006, 12:12 PM   #7
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Oil pan gasekt is fairly straight forward. Torquing it is the EASIEST part of the job as the bolts are a straight on access. (Maybe Hans can shoot me a pm as to why in all Potatoland.....that torquing would be hard???)

The intake gaskets are most likely (if original) in need to be replaced with a newer designed gasket made with an aluminum frame. However the oil you see is probably from your valve cover gaskets and pretty common.
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Old 10-11-2006, 12:50 AM   #8
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Besides what I posted in the other rear oil seal thread....

http://www.bonnevilleclub.com/forum/...ic.php?t=63772

..here'* some information that perhaps you can give to your mechanic about sealing the oil pan. This is another of GM'* technical service bulletins. As Bill said, the oil pan removal and installation is fairly straightforward. The only thing to watch about torquing is to use the proper amount....as always.

Quote:
This bulletin is being revised to change the procedure for greater ease of installation. Please discard Corporate Bulletin Number 01-06-01-008 (Section 06 - Engine/Propulsion System).

Condition

Some owners may comment on a repeat engine oil pan leak.

Cause

The engine oil pan leak may be due to an uneven (rippled) sealing surface on the oil pan.

Correction

Seal the leak with RTV sealant using the following procedure:
1. Remove the oil pan from the engine. Follow the oil pan removal instructions found in the Engine Mechanical section of the Service Manual.

2. Remove the old RTV sealant from the engine block at the joint face sealing surfaces and the oil pan. Use only a plastic or metal scraper as described in Corporate Service Bulletin # 00-06-01-012.

Important: Ripples which appear in the oil pan sealing rail surfaces of the oil pan will not affect sealability when using this procedure. Do not replace the oil pan for this condition.

3. Inspect the oil pan sealing rail surface for bends or distortion which would affect sealability.

4. Clean the engine block and oil pan mating surfaces using a solvent that leaves no residue, such as P/N 12346139 (in Canada, P/N 10953463), or equivalent.

Important: In the steps that follow, it is strongly recommended to use a 5 oz. (142 ml) RTV sealant cartridge and a hand-actuated caulking gun. This will help assure that a continuous bead of RTV sealant will be applied to the gasket surfaces.

5. Use a new oil pan gasket and windage tray assembly, P/N 24502397.


6. See the illustration. Apply a continuous 1/4 inch bead of 5900 RTV sealant, P/N 12346286, on the top of the new gasket. Apply RTV sealant directly over the gasket'* raised sealing bead.

7. Install the oil pan gasket and windage tray assembly to the cylinder block. RTV will hold assembly in place temporarily.

8. Install the oil pump pipe and screen assembly.

Tighten

Tighten the oil pump pipe and screen bolts to 15N.m (11 lb.ft).


9. See the illustration. Apply a continuous 1/4 inch bead of 5900 RTV sealant, P/N 12346286, to the bottom of the new gasket. Apply the RTV sealant directly over the gasket'* raised sealing bead.

10. Install the oil pan on the engine.

Tighten

Tighten the oil pan retaining bolts to 14 N.m (124 lb in).
11. Follow the remaining oil pan installation instructions found in the Engine Mechanical section of the Service Manual.

12. Before adding engine oil, allow the RTV to set for 30 minutes.

13. Add the proper amount of engine oil, then verify on the dipstick.

14. Run the engine and verify the repair.
And I've never heard of something "wearing out" from not being used.
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