Oil leak... Rear main seal, or oil pan?

[95CobraMike]

I just put an engine in and i have noticed a little leak from either my rear main seal or my oil pan gasket. the oil drips down from the back side of that little skinny plate that goes between the block and the bell housing if i drive it and then park it overnight i have about a 6-8" circle under my car in the morning....
What do you think it is? will i be ok till winter? as long as i keep checking my oil level?
thanks

 

[281pony]

im having the same issue with mine, just not as big of a leak.

i think its actually the rear main. i rtv'd the hell out of my pan where it appeared to be leaking from and it still does it. you should be ok if you keep checking the oil as you mentioned.

 

[5spd GT]

A 6-8 inch puddle is a pretty decent leak. I'd almost guarntee you that is a rear main seal leak. The oil pan won't leak at a stand still (I wouldn't think) but the rear main could because where it is located at.

 

[Pokageek]

I have the same ^%&*! problem with my new 306 install. I called the manuf and they said rear main seal is unheard of and prob oil pan gasket or valve cover gasket.

Well, it looks like its comin DIRECTLY outta the area between the eng and trans so it prob IS the rear main. ARGG!!

Mine aint leakin that much though, like a 2" spot in the morn and never drips when cars off. Still sucks.

 

[HISSIN50]

Is the clutch slipping yet?

I would degrease the entire motor and then get it on a lift and watch it. If it is valve covers or something up top, you can see it. If it is the pan, you should see a snail trail. Deduction leaves the RMS if that is what is left.

I am not familiar with your combo, but you have made crankcase ventillation accomodations for the 10 PSI, right?

Good luck.

 

[94-302-vert]

I would also thing rear main seal, and if you are running a manual trans I would go in and change it as preventative measures before it takes the clutch with it. With an auto if you keep up on the leaking oil and don't mind the spot in the driveway then you should have no problem making it to winter.

 

[95CobraMike]

i do not have any crankcase ventalation... are you talking about the little filters that go in the place of your engine oil cap?

 

[RowdyRed94]

I replaced my rear main seal when I did my clutch. I had previously changed to Mobil 1 and it started seeping. It still leaks. I'd suspect the oil pan where it curves around the cranshaft opening.

 

[HUNTED]

It is most likly your rear main that is leaking you might have to go to a slightly bigger rear main seal

 

[5spd GT]

This is the worst ever rear main seal leak I have ever had and it's been going on since April. It leaves a nice smoke show behind me when I go wide open throttle for a few seconds. My CF Stage II still doesn't slip. The rear main seal is behind the flywheel. The clutch disc/pressure plate is on the other side of it. It is kind of hard to get oil in there but it can happen.

 

[HISSIN50]

i do not have any crankcase ventalation... are you talking about the little filters that go in the place of your engine oil cap?

Yeah, some sort of crankcase ventillation (PCV, valve cover breathers, a vacuum pump, the oil fill cap breather [which is a valve cover breather], etc). You need some sort of decent ventillation. Otherwise with no breather, you bottle-neck the blowby and it will take the path of next-least resistance, which is often front and rear crank seals. And as air is expelled, oil goes along for the ride.

If you dont have bi-directional breathing capability, at times you will be sucking air IN through the crank seals, which is not good for them either. Furthermore, after the seal is fixed, if there is a ventillation issue, the new seal can leak again.

That is an insane oil leak. You might need to use a sleeve when you fix it. I am with David - I still cant believe that the seal is that far gone.

Good luck.

 

[slytherin]

Mine only leaks after she has been sitting for a while same spot as previously described. I thought it to be the oil pan and retorqued it when I did the tranny swap I should have done that real seal- ughh! maybe this winter as it is not that bad of a leak.

 

[95CobraMike]

a few questions....


if my crank was turned down .010mm, does that mean i need to get diffrent sized rear main seal? cause i didnt

this will cause me to have smoke behind me when i get into it??

where can i get a valve cover breather type thing?

thanks

 

[CManT1914]

a few questions....


if my crank was turned down .010mm, does that mean i need to get diffrent sized rear main seal? cause i didnt

this will cause me to have smoke behind me when i get into it??

where can i get a valve cover breather type thing?

thanks

I don't knoe about the crank clearances or whatever, but you can get breathers at most parts stores (Advanced Auto, O'Reilly's). That's where I got mine.

 

[95CobraMike]

a few questions....


if my crank was turned down .010mm, does that mean i need to get diffrent sized rear main seal? cause i didnt

this will cause me to have smoke behind me when i get into it??

where can i get a valve cover breather type thing?

thanks

ttt

 

[Alec]

ttt

Unlikely. I have seen seals cut grooves in cranks, hence the sleeve mentioned above.
My Fox did the same thing. I replaced the seal and it was still "leaking". My 95 is wet around the pan also and leaves a small spot. So I am thinking it's just the pan/rubber gasket combo on the 5.0's. You drive it, oil blows back hard to trace.

But a 6" puddle! thats not the gasket "weeping".

Remember the 302 H.O stock intake has a little screen or filter under the PCV valve, sometimes it gets carbon buildup and the motor can't vent. It is a bitch to get to, but you need to clean it or replace it. When you ask for it tell them you want "Motorcraft Crankcase Vent Oil Separator or Crankcase breather" Wix might make it too. It's hiding under the grommet in stock setups. Just a thought.