Rear oil leak when driving only

fritznbud

fritznbud

Senior Member
Hey all, After searching and reading every previous post ever posted, i cannot find anything on this topic except the rear main shouldn't be the cause of my leak. I start my car and let it warm with no leaks. I shut down the car and the leak stops after a few seconds. But after putting a load on it, driving a couple of miles i will stop and look under to see a small stream just forward of the flywheel housing and not through the cotter pin hole. Not enough to have to add oil yet. I have an oil pan gasket set and am ready to fix this leak but am not sure if the gaskets will do the trick. I've replaced the oil cap and checked out the obvious. Any suggestions on this type of leak? Thanks
 
Pan bolts tight? Not super tight to crush gasket! or maybe they were already tight to crush gasket!
 
Sounds like a bad thrust. You can check this by having someone to sit in the car and push the clutch in while you pry the crank pulley rearward. Just pry the pulley to the rear (gently but firmly) and let it go. Have the person in the car depress the clutch pedal and see how much the crank (pulley) moves forward. It should not move but between .004 and .012 thousands. If it moves more than this you will have a leak. The reason for this is, when the crank moves it will pulsate forward and rearward. As the crank moves rearward it pulls oil from the bearing into the void and return channel. When it moves forward, this oil is forced under slight pressure into the channel, overwhelming it and causing the overflow into the flywheel housing.
There is no proper cure except to have the mains re-poured and re-bored. perform the check and see if this is your problem.
 
Thank you James. I believe your right on this one. Especially when you said overflow into the flywheel housing as i'm seeing the oil come out there and thinking it's probably filling up. That saves me the oil pan gasket job because after reading some slightly scary posts here, i'm going to pass on dropping the pan. I'll be installing a janitor and driving her on for now.
 
I would wipe the area very clean and dry, then inspect very carefully for the source of the leak. Seem to me like it might be the pan gasket or a leak from the rear of the camshaft. Do you have the block to flywheel cover gasket installed? Some people just use silicone and no gasket.
 
Tom Wesenberg said:
I would wipe the area very clean and dry, then inspect very carefully for the source of the leak. Seem to me like it might be the pan gasket or a leak from the rear of the camshaft. Do you have the block to flywheel cover gasket installed? Some people just use silicone and no gasket.
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Tom, if the crankshaft thrust is too far from 'spec', as the crank moves fore & aft it just pushes the oil out no matter how tight the babbitt to crank journal clearances are. Also think what this is doing to the camshaft timing and ultimately the ign. timing.:eek:

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I have the same problem. Leaking oil down the front face of the flywheel housing but not through the cotter pin hole. I am hoping it is the oil pan gasket specifically where the two gaskets interface. However, a problem with the camshaft gasket has also crossed my mind. Is there an easy way to figure out if the leak may be camshaft seal related or is this a trial and error thing?

http://www.fordbarn.com/forum/showthread.php?t=30803
 
BRENT in 10-uh-C said:
Tom, if the crankshaft thrust is too far from 'spec', as the crank moves fore & aft it just pushes the oil out no matter how tight the babbitt to crank journal clearances are. Also think what this is doing to the camshaft timing and ultimately the ign. timing.:eek:

.
Click to expand...

Yes, I understand the need for correct end play, but wouldn't that oil leak be be more likely to show up at the cotter pin rather than from the front of the flywheel cover?

A leak at the rear of the cam should be the same no matter the engine speed, but a leak at the pan gasket might be more with more engine speed because so much more oil gets thrown around at higher speeds. I'd first look for a pan gasket leak.
 
I have read your post a couple times and you state the leak is outside of the flywheel housing…I agree with you that that fact alone pretty much rules out a rear main leak. If the leak is outside of the flywheel housing, (not dripping from the cotter) it is likely coming from the pan gasket or the rear main cap cork gasket. Another indication it is the pan is that it is leaking primarily when the engine is running. Tom W. says it may be a leak from the rear of the camshaft opening in the block but I don’t think so as I have found that particular leak continues to leak for some time after a warm engine is stopped. Reason: The oil in the valve chamber continues to supply oil to the rear cam journal until the rear reservoir has drained below the rear main and cam bearing openings, thus the extended leak after stopping. I suggest cleaning the entire bottom of the oil pan and pan flange, the pan area adjoining the flywheel inspection cover which seats on the rear main cap cork gasket and the flywheel inspection cover as it also rests against the rear main cork gasket. Start the engine let it warm up and drive it...park it and then follow the leak back to its source. Look closely at the ends of the rear main cap cork gasket as it may have shrunk opening a path to oil being splashed when the engine is running at a higher rpm. Since it isn't leaking at idle, there may not be enough oil splash to fully wet the area it is leaking. It is probably a pretty small opening as it takes warm oil and higher rpm to make it leak. There is a chance you have a slight amount of wear in your rings and exhaust valve guides that are slightly pressurizing your crankcase when running at a higher rpm. All these factors can contribute to the cause of the leak you are describing.

Added after seeing Tom's updated post: I agree with Tom...it is not sounding like excessive end play as that leak would show up at the cotter.
I stand with Tom...check the pan and rear main cork gasket first.

Good Day!
Dave in MN
 
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Thanks you guys....Dave, it leaks at idle, when i pull over and check after driving 3 miles. It's just this side of a stream meaning it is a fast drip that turns into a stream. After 8 to 10 seconds it slows to a drip. I'm thinking that after braking, and things settle to flat and level, the true leak is the dripping part and the stream is alot of motion pushing it along. I may as well change out the pan gasket and hope i dont walk into a tough job. There isn't one soul in this "Deliverance" home town to help me so i work alone. May i add, this motor runs perfect, torque and power galore and never a miss, even running an air filter. You have to watch when you start her to just tap the starter it starts so quick, and i run her with 1/8" GAV adjustment.
 
If the drip is coming down the front of the flywheel housing, change the pan and valve cover gasket. If it is coming from the hole in the bottom of the flywheel housing, don't waste your time with new gaskets, you need new mains. Simple as that.
 
It doesn't leak at all through the hole in the flywheel, where the cotter pin is. The valve cover has no leaks. So i'm going to replace the oil pan gaskets, i picked up the set from Smith & Jones last friday down here at the A club swap meet. I've done all of the obvious like the oil cap, pan bolts and everything else that has been posted here from the search tool.
 
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