Engine Oil Leak Only When Engine's Cold

FoxbodyStang1990

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Feb 20, 2017
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So I recently purchased a 1990 Mustang GT, so far it doesn't leak anything beside a little power steering fluid (or radiator fluid I'm not sure). Anyways it leaks a little bit of oil from where the oil pan meets the bellhousing. The weird part is that it only leaks when the engine is cold, It can go 2+ hours after the engine is off before it starts leaking and seems like it then only leaks for a few hours before stopping (maybe something draining?). Thanks in advance.
 
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JosephV

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Feb 20, 2017
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Remove the oil filter to see whether it was double gasket-ed. Sometimes when the oil change was done, the old filter gasket could've stayed there when the new filter was put on.
 

FoxbodyStang1990

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Also, wouldn't a rear main seal leak all the time even when running. I have a rear main seal leak on a '69 Oldsmobile and it leaks all the time no matter what.
 

General karthief

wonder how much it would cost to ship you a pair
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Aug 25, 2016
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Not that much, leaves a spot maybe half a foot in diameter and then stops.
Thats a fair amount of oil, so I understand, the leak comes from the bell housing when you turn off the engine, does not leak when engine is running. And it's not the rear main, that would leak when the engine is running.
Ok, first lets establish that it is motor oil and not trans fluid, place a pan under the area the oil comes from and capture a sample then see if it is oil or trans fluid.
I suspect its going to be a rear main I just cannot figuare why the leak acts like it does, can you take a mechanics mirror and look behind your intake for a leak where the lower intake meets the block, also check the valve covers back by the firewall.
You can get that little mirror on a stick at any auto parts store
 

Dan02gt

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Mar 2, 2003
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My money is on rear main seal or the rear of the intake. I think what's happening is that it takes a while for the oil to run from where ever it's leaking to where you can see it.
 

FoxbodyStang1990

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It's definitely motor oil, it's black not red. Looked up at the leak and you can see it pooling up at the top of the oil pan and seeping down the front face of the bellhousing. I will check the intake and back of block. Hopefully it's not the rear main but I guess it's not the end of the world if it is.
 

FoxbodyStang1990

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Is there any way this could be an oil pan leak, the gasket looks absolutely mutilated, but only leak is on front of bell housing.
 

Davedacarpainter

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Use a can of brake cleaner and clean the crap out of the pooling oil area. Warm the engine up and take a look.

Just have a good light so you can see where it's leaking from.

I'm thinking rear main seal as well, but it could be the oil pan gasket. I would be kind of surprised if it is that unless you've had it off recently to do some bottom end work.
 
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