Oil leak , rear main seal? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 06-12-2007, 09:21 PM   #1
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Default Oil leak , rear main seal?

I am getting the '95 ready to gift out, and I was going to replace the oil pan gasket because I have had an annoying, but small, leakage over the past year.

I put it up on the ramps to see if there was anything to do, more than in the Chilton'*. The pan bolts all have drips hanging on them. I haven't changed a pan in 35yrs, but i don't remember them leaking symmetrically all the way around. There'* also oiled gunk on the plastic flywheel cover and it looks like there is some above it on the engine. looking from above the engine down, I'm not seeing anything dramatic from the valve cover or back LIM.

Isn't the rear main seal somewhere up above the trans on the driver'* side? If so I'll need to know what to look for. I guess I'll have to degunk that entire area, then run it.

Any thoughts or suggestions would be appreciated.
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Old 06-13-2007, 12:41 AM   #2
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The crankshaft rear seal is a spring loaded lip seal that is driven into an aluminum carrier bolted onto the rear of the block. The flexplate is bolted to the end of the crankshaft and covers the seal and the carrier. If you remove the plastic covers and look up on the engine side of the flexplate, that would be where a rear seal failure would be likely to be seen. It would leak the most when the engine is running.

Check out the oil sending unit on the passenger side rear, also. These can crack and put out a lot of oil.
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Old 06-13-2007, 08:05 AM   #3
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In my experience.. if the leak begins at the rear of the engine, it is a good chance that the rear engine cover bolts have loosened.

I also thought rear main seal, when the trans was out..there was no signs of an oil leak. Many pan gaskets later, still leaking. Upon pulling the motor, I found the bolts holding the rear cover (rear main is in this cover) bolts to be less than finger tight. Actually..they were extremely loose.

Since tightening them (on all three motors) I have not seen a single leak. This leak is the reason I switched to a 2000 + oil pan.
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Old 06-13-2007, 12:12 PM   #4
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Quote:
Originally Posted by BillBoost37
In my experience.. if the leak begins at the rear of the engine, it is a good chance that the rear engine cover bolts have loosened. (snip) .
Thanks guys.

I finally found the section in my '96 FSM. Is that engine cover the "Crankshaft rear main oil seal housing"? I'm going to do what Bill Buttermore referred to, first I'm going to clean out the whole area, then run it. It looks like if either the seal or housing in leaking, the transaxle or engine has to come out. I'm not equipped for that, though.

I'm po'ed because I should have checked this sooner. We're tryin' to help out one of the families in town, the last thing I want to do is give them a car with a headache.
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Old 06-13-2007, 01:52 PM   #5
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Charlie..

The level of my leak was never a headache. More of a personal thorn in the side. I would wipe the pan and filter each time I changed the oil and it never left a drop of oil in my garage.

It is possible to remove the torque axis mount, unbolt the transmission and slide the engine forward about 4 inches to do this..however..Merely tightening these bolts would solve the issue if it'* the cover and not the seal.

Having the car in the air at Intense, I was allowed to quickly look at the rear main seal. I couldn't see a darn leak at all and figured it was my oil pan gasket.....STILL????

Pulling the motor and talking to Bob.. aka Echo.... he said they found Ben'* bolts to be loose. (Probably not the only screws..hehehehe). I tried it and found them to be pathetically loose.
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Old 06-13-2007, 10:34 PM   #6
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Bill

I also have had a leak for quite a while. It will leak after I shut the car off on the driveway. The leak will create about a 3 inch diamerter stain. I can also smell oil, like it is hitting something hot--like the exhaust manifold maybe. It does not seem to leak when the car is idling though.

The bolts that you are talking about tightening, do you need to seperate the engine and trans to get at them?

Thanks
Andy
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Old 06-14-2007, 01:01 AM   #7
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Quote:
Originally Posted by Andy King
Bill

I also have had a leak for quite a while. It will leak after I shut the car off on the driveway. The leak will create about a 3 inch diamerter stain. I can also smell oil, like it is hitting something hot--like the exhaust manifold maybe. It does not seem to leak when the car is idling though.

The bolts that you are talking about tightening, do you need to seperate the engine and trans to get at them?

Thanks
Andy
I would look at valve cover gaskets for this one.
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Old 06-14-2007, 08:53 AM   #8
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Andy... yes you would have to seperate for the bolts I was mentioning and yes..I agree with Sonoma..the leak you describe is probably a bad valve cover gasket.
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