oil leak

B

ba49

Senior Member
I recently bought a 30 coupe and I'm new so I looked through the archives but didn't find a solution for my problem. I have a bad oil leak but it doesn't seem to leak when running. (Except when it overheated once it left a trail of oil down the street and driveway.) When I shut it off it steadily streams out of the flywheel cover them after a few minutes slows to a drip. After about ten minutes the drips slow up alot.When I looked at it through the removed flywheel inspection cover I could see it dripping from the rear main in the center between the bolts.I pulled the pan and the drip tube was attached to the cap. I'm not sure where to go from here. I'm really getting frustrated with this car but I really like her. Sorry if this was adressed before.
Bill
 
if im not mistaken that means your rear main bearing is pretty bad and allowing oil to flow past its groves and into the flywheel housing.
 
Drain holes in rear main cap could be plugged not allowing the oil to drain back to the drain tube . In my case the rebuilder put a rope seal in the same groove the slinger goes in . Rope seal came apart and pulged the oil passages . You might want to pull the rear main cap and see whats going on .
 
I had the same problem and it was as simple as a $5 oil cap. The old cap had the tabs bent down and was pushed too far down. I was panicking because the oil was pouring out same as yours. Some nice folks on here suggested I try a new oil cap. Five bucks later...problem solved. Hope yours is as simple.
 
Try the easy things first. The oil cap is a good first try. Also drain the oil and look for pieces of metal in the old oil; that will tell you if the babbitt is coming undone. If you see metal, drop the pan and visually check the bearings for obvious damage. Metal might mean your bearings are shot. These things will give you some idea about how serious the problem is.
 
Last edited:
I did drop the pan and I didn't find any chunks. I did find a very small amount of pieces about the size of a grain of sand. The pipe appears to have been welded in place. Would blowing some compressed air in the pipe help? Would it hurt anything? I'm hesitant to remove the rear main cap because I'm new to all of this.Can it be done inside the flywheel cover? I didn't notice any chunks missing from the babbit that I could see. The oil cap does have a flex hose attacted. The PO said he dropped the pan to clean out the sludge. I'm wondering if he discovered something he didn't like? He bought it in 08. Before that it sat in a dealership showroom for 35 yrs. The PO said the motor was rebuilt, but had no details. I did notice some copper rtv visible arould the rear main cap near the seal so I'm may have been rebuilt.
Bill
 
Their is a long list of "What it might be" but a few things to check first. I had a similar problem that was caused by someone putting a steel wool pad in the oil cap to help with blow by. Well it helped with blowby but it also pressurized the oil system which caused the oil to leak out the back. Antique Engine Rebuilders have an excellent article on rear main leaks. Look at this link and it may help shine a light on your problem. Rear Main Leak
 
I had the same experience as sconnors, pull the cap all the way off and try it. The positive pressure that can build in the crank case will push the oil up the rear tube and.... under pressure push it out the rear bearing no matter what shape its in.
 
Thank you for all of the feedback. I will try the simple things first. What I'm having trouble understanding though is why the oil leaks out AFTER the engine shuts off and not during? This leads me to think maybe something is not draining back to the pan fast enough, like the drain pipe is plugged? If it were bearing clearance or cracked babbit wouldn't it be more likely to leak while running? Sorry if I'm missing something.
Bill
 
I am guessing that your rear main actually is leaking while running, and leaking into the flywheel housing where it collects and drains out the hole with the big cotter pin. Also, after you shut down the engine there is a process of the valve galley oil draining that can contribute to leakage after you shut down.
 
ba49 said:
Thank you for all of the feedback. I will try the simple things first. What I'm having trouble understanding though is why the oil leaks out AFTER the engine shuts off and not during? This leads me to think maybe something is not draining back to the pan fast enough, like the drain pipe is plugged? If it were bearing clearance or cracked babbit wouldn't it be more likely to leak while running? Sorry if I'm missing something.
Bill
Click to expand...
I don't type as well as I would like so I can't tell you why it leaks like that here in detail but, that is a symptom of a bad rear main bearing. The crank is riding on a cushion of oil when running and the oil is circulating from the pan through the motor and back to the pan like a pump when running but when it stops the circulation is done and the crank settles to the bottom of the bearing it allows the clearance to be all at the top and the oil overwhelms the rear return and leaks out the bottom of the flywheel housing. You might clearance the main and get some relief if it is not cracked or broken. In that case you will have to have new bearings. Don't remove the tube from the cap if you pull it, just blow through it and make sure it is clear. Most tubes are welded to the cap and if you can't cut the weld and replace it, don't try it.
 
Recently I saw a fresh new rebuilt engine where the customer had assembled the short block. It leaked oil after shutdown. Did not leak as much when running.

The problem was that the owner had used WAY to much silicone gasket sealer on everything. Silicone sealer was applied so thick that it that had ozooed out from between the pan and was found in gobs all over inside the engine.

A chunk of sealer had found its way into the rear main cap and lodged in the entrance to the main cap drain tube. Blowing air in the drain tube seemed the tube was clear but leak continued.

Removing the main cap revealed a gob of sealer that had been floating around and was stuck in the entrance to the oil drain tube where the oil channel changes direction from horizontal to vertical and enters the drain tube.

This guy must have used 2 tubes of sealer just on the pan and valve cover gaskets.

A light coating on gasket surface is all that is needed!
 
Thanks guys, I'm going to pull the cap today. I have some plastigauge coming today also. I'll let you know what I find. You guys are the best help a newbe could find. Last winter I totally rebuilt a vintage T-bucket but this is a whole new ballgame. I think I'm hooked. I even have the Bucket up for sale.
Bill
 
A friend of mine wired an aluminum turkey pan to his flywheel housing to catch the leaking oiland then poured it back in the engine
 
The leak could also be coming from the back of the cam . There is a gasket around the fly wheel housing cover . The gasket also covers up the back of the camshaft . If this gasket is torn oil will leak out from the back of the cam and drain down into the fly wheel housing. Mine was not only leaking from the plugged up main drain system it was leaking from the back of the cam . In the end I pulled the engine and fixed both leaks . Now I am glad I pulled the engine as I would not of found the leak at the back of the cam if I had not pulled the engine . If all the easy remedies do not fix the leak ,in the long run you will probably be better off pulling the engine and checking all possibilities . It is a lot easier working on the engine on an engine stand .
 
ba49 said:
Thank you for all of the feedback. I will try the simple things first. What I'm having trouble understanding though is why the oil leaks out AFTER the engine shuts off and not during? This leads me to think maybe something is not draining back to the pan fast enough, like the drain pipe is plugged? If it were bearing clearance or cracked babbit wouldn't it be more likely to leak while running? Sorry if I'm missing something.
Bill
Click to expand...

The oil stays in the flywheel until you shut down the car. Then it runs into the flywheel housing. Two big problems that make a oil leak, are a loose rear main and to much end play. But there are many more things that can do it.
 
Mine tends to leak until the oil level gets about 1/2 way between the F and L on the dipstick. I also have a steep driveway thinking some oil is dumped into the rear main before I shut down.
 
If the portion of the main bearing that takes the thrust is bad then the crankshaft will move back anf forth along the longitudinal axis and will pump the oil out of the rear main . You can check this by having someone push in on the clutch while you observe the crank pully . If you see the crank pully move towards the radiator at the same time the clutch is pushed in you more than likely have a bad thrust bearing . You can also check the run out on the end of the crank shaft using a gauge .
 
You must log in or register to reply here.
Back
Top