VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 31 oil leak at rear of engine

I recently removed the oil pan and cleaned about a ½” of gunk from the bottom. I also cleaned the troughs above the main bearings and anything else I could access. Filled it with 10W-30 and my oil pressure improved from about 5 to 10 psi. warm. I didn’t run the engine much before the cleaning but did not notice any major leaks. Now I have a steady drip when running just above idle. When I shut the engine off, oil runs out in a steady stream for about 15 seconds. It is not the pan gaskets. It appears to come from behind the rear main bearing. It runs down the front face of a sheet metal cover that the clutch cover tucks into. I can see the front of a cover that is just behind the main bearing by looking between the oil pan and the cross member just ahead of the flywheel. The oil is running out from behind this cover. I have read on this forum about a check ball in this area. Could this cause the leak? What should I try to fix the leak?

Thanks for any info.

Joe

Yes.

If the ball check valve in the rear main bearing cap is stuck in the "closed" position, oil cannot return back to the oil pan and it will leak out through the flywheel sheet metal covers. If that is the case, you will have to remove the oil pan to check the position of the ball check valve. You can either clean out the passage way that contains the ball check valve, or you can remove the ball check valve completely.

Another thing that would simulate the same type of oil leak would be the valve cover gasket. Check the back of the valve cover gasket and the cylinder block to see if oil is leaking there as well.

can i access the check ball without removing the rear main bearing?? i did not notice it when cleaning the trough etc, the valve pan gasket is ok.

thanks.

joe

Yes.

is there a cutaway drawing or picture of the check ball location available??? my parts list / repair manuals do not show it.

thanks

joe

Once you remove the oil pan, the ball check valve location on the rear main bearing is obvious.

I sure hope so.... i somehow missed it the last time. :-(

thanks.

joe

I have removed the oil pan. attached i hope is a picture of a hole in the front face of the rear main. It looks like a pin is coming down from the top. Is this what is plugged and causing the oil to run out of the back of the engine? how can i determine if it is clear? or am i looking in the wrong place.

I don't see a spring or a check ball.

http://i1105.photobucket.com/albums/h355/joe15747/oilreturn.jpg

thanks for any info

Joe

The pin holds the ball in the passage. There is no spring just gravity to position the ball. The passage is tapered so when the car is parked with the back of the car well below the front the ball seals off the passage. As long as the passage is clean the ball does not impede the oil flow. If the leakage of oil out of the rear of rear main bearing is not too great and the passage is clear no oil will leak. Because of normal movement of the crankshaft the rear main bearing wears more on the back side than front. Eventually that produces more oil flow out the back. When it exceeds the capacity of the passage to drain it away oil leaks. Typically measurements are not made to show the taper and the method to set the rear main will not result in eliminating the leak. Putting plastigage across the bearing (in line with the crankshaft) may show the taper.

Thanks for the detailed explaination.

What is the solution? How should I proceed?

Does the main bearing lower cap need to come off to access and clean the passageway? Any special precautions?

Is the ball really necessary?

Should I remove the ball and if so, how?

Before I removed the pan the first time for a thorough cleaning, I didn't notice the rear engine oil leak, so perhaps something happened while cleaning the trough above the rear main bearing?

Thanks for all the help.

Regards,

Joe

To clean the passageway, it would be easier to remove the rear main bearing.

Is the ball really necessary? No.

To remove the ball check valve, take out the pin in the front of the main bearing and then the ball will come out.

I removed the main bearing and cleaned the ball and passageway.

To remove the pin and ball does the bearing shell need to be removed?

What are the chances of the ball getting stuck again?

Also what is the number 4 stamped into the back side of the housing?

how difficult is removing the bearing shell and getting it back in correctly

Thanks for any advice.

Joe

http://i1105.photobucket.com/albums/h355/joe15747/mainbearing.jpg

http://i1105.photobucket.com/albums/h355/joe15747/main-bearing.jpg

It is easiest to remove the cap to remove the pin.

If the passage and ball are cleaned the chance of ball sticking are very small. If clean oil is maintained in the engine then sludge will not stick the ball again.

Have no idea why the 4 stamped on the housing.

The bearing shells can be carefully snapped out and replaced. The center main is toughest but carefully tapping with soft piece of wood between hammer and bearing shell on the edge can get it done. Easy on the cap but tough on the part in the block.

Thank you thank you for all the help.

i took the 31 for a short trip around the runway today and i think the oil leak is fixed. :-)

if the clearance in the rear main bearing gets excessive, especially more wear towards the back, would all the oil be able to get past the check ball??? seems like the passageway is really restricted by the ball.

is the oil checking dip stick supposed to be perfectly straight or does it have a bend??

regards,

joe

Dip stick is straight. Actually the ball does not restrict the flow when it is down by the pin. The taper of the passage takes care of the area taken by the ball.