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Oil Leak Source

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Old 05-11-2018, 04:16 AM   #1  
NJey1985
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Hi All,

I am trying to chase the source of an oil leak. I have jacked the car up and looked around the rear main seal area.

See below the pictures of oil on the bell housing inspection plate cover inner and outer. Note that this plate has been cut to accommodate the starter motor.
Outer side facing toward engine
Inner side facing toward flywheel

I have swabbed the rear main seal area with a q-tip and there doesn't appear to be recent oil residue. See pictures.

q-tip swab around rear main seal areaPictures of the rear main seal area.




Based on the oil residue on the bell housing cover plate compared to that of the q-tip swab and pictures in the area, the rear main seal or oil pan gaskets are not the source of the leak?

Car is 1969 427 C3 Corvette.

Thanks in advance for any advice.

Last edited by NJey1985; 05-11-2018 at 04:17 AM.
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Old 05-11-2018, 06:32 AM   #2  
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Because of the wet spot on the cover is dead-center, I would suspect the rear china wall but not either valve cover gasket. Oil pan / rear seal looks really good. What does the top of the bellhousing look like?
And, where is your oil pressure sending unit fitting on your car?

Last edited by HeadsU.P.; 05-11-2018 at 06:41 AM.
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Old 05-11-2018, 12:45 PM   #3  
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Oil pressure sender on a BB is over the oil filter.
How much oil are you having to add to maintain the level? From the looks of your pictures of the rear pan and crank- there is no leak unless you have cleaned it pretty well.
I'd look at the back of the intake and the distributor gasket, but with no oil showing on the pan, it's anyone's guess.
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Old 05-11-2018, 05:04 PM   #4  
NJey1985
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Quote:
Originally Posted by TimAT View Post
Oil pressure sender on a BB is over the oil filter.
How much oil are you having to add to maintain the level? From the looks of your pictures of the rear pan and crank- there is no leak unless you have cleaned it pretty well.
I'd look at the back of the intake and the distributor gasket, but with no oil showing on the pan, it's anyone's guess.
I am not having to put any oil in the car. That said the car rarely gets driven. Pictues are of the block uncleaned.

I know the valve cover has a leak which is dissapointing considering the mechanic installed brand new felpro rubber gaskets. I would have thought with the rubber gaskets they wouldn't leak and if the did it would be minimal, hence i suspected multiple sources for the leak.
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Old 05-20-2018, 02:45 AM   #5  
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Hi all,

Just following up, the top of the bell housing seems to just be greasy, I can't really see any oil film.

Intake manifold has had new gaskets and sealed up recently.

Back of the block leading down from the valve covers is dry. The valve cover has a very minor leak but drop straight down on the ground as opposed to running back down.

I used a endoscope and tried to grab a better look at the rear main seal and the oil pan gasket. I cleaned the bell housing cover re-installed and ran the car, there is a dribble right in the middle of the cover. Without the cover there is oil on the inside of the bell housing.

I can see the rear main is blue which leads to believe it's a felpro one?. The car was last rebuilt in 2008 according to the receipts I have.

Just after some thoughts on the pictures, apologies for the quality, the endoscope has a mirror on it and the tight space and focal length of the camera didn't help.

I am leaning toward the rear oil pan gasket seal based on the pictures....if I need to do the oil pan gaskets should I do the rear main seal since its been 10 years. I don't believe it is leaking. locations of the endoscope




Felpro seal I am guessing?

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Old 05-20-2018, 07:10 AM   #6  
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If you chose to drop the pan, then yes, what a great time to change the rear main seal.
Just drop the oil pump and decide if its a keeper or not. How is the pump driveshaft?

FelPro has very good rear main seals, some come with a little tool to help ease it in there. Idler arm has two carriage bolts, two nuts that will have to be removed. That will drop the drag link just enough to get the pan out of there.

Some people swear by the one piece FelPro oil pan gasket.
Some people swear AT the one " " (still leak).
One good investment is oil pan stud kit ($22) makes installing gasket / pan sooooo much easier. Allow the gasket / RTV set-up overnite and you will not get squeeze out.

The higher you can get the front end off the ground the better. Its not too bad a job.
Good Luck

Last edited by HeadsU.P.; 05-20-2018 at 07:12 AM.
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