The Stovebolt Site Forums The Shop Area Engine Shop Rear main seal

Hi Bolties! Drove the old truck yesterday and noticed an oil leak when I got home and parked it on the inclined driveway. I observed the oil coming from the hole in the flywheel cover. The engine only has about 200 miles on a rebuild, if that. Was rebuilt last May. I feel it is probably a rear main seal. The engine is a 1957 235. Need to know if the wick seal was still used that late in the game. Also, thoughts on removing the pan and rear main cap to replace the seal with the engine in the truck. Thanks for the advice!
KT

Changed mine a few years back and there was a rubber-type seal in there. I replaced it with a FelPro rubber-type. Dropping the pan is fairly basic. Remove the cap and remove pry out the bottom half of the seal. The top half can be pushed thru if it is a rubber-type. Once the end protruds grip it with needle nose pliers and pull it out. Be careful with scratching anything. If you are lucky you can get by without loosening the other caps and dropping the crank a small amount.
When you put the seal in try to stagger the joint so that it is not in line with the mating surfaces of the cap and block. In other words put the ends of the seal at a 2 o'clock and 8 o'clock position. This will help keep oil from leaking past at the block/cap joint.

I have mentioned this before and it should be checked before you conclude the rear main needs to be replaced.

The crank shaft flange that the flywheel bolts to has two or three holes in it other than the bolt holes which the crank shaft bolts go into. These "other" holes are supposed to have alignment pins in them which allows the correct allignment of the flywheel. If the pins are not in the crank holes, the bolt holes can be used to align the crank so consequntly the pins are left out by some rebuilders. If the pins are not in the holes, those holes go through the crank flange into the bottom cavity of the engine. When running, the engine will "pump" oil out of those holes, throught the flywheel and right onto the clutch and it will run out of the hole in the flywheel cover.

I had this happen to me. Unless you know for sure the pins are in the holes, I would not assume the seal has gone bad. I would check the for pins. If you need pins, you can get them at a parts store. Do not cut off bolts and put them into the holes. Use pins and they will have to be driven into the holes. I did this and it solved all the problems.

I also put in a new seal before I found the pins missing.

Good luck!

SixCyl-

I missed this before, thanks for mentioning it again. I have a '54 GMC leaking oil and this could account for some of it. Gracias!

This brings up another question for me. If the pins are missing, can the flywheel be installed in the wrong position? I can't align the timing ball with the pointer when trying to set the ignition timing. Plus, I have an oil leak.

Thanks!

Doug

:confused:
I have been told that it is possible to install the flywheel without the pins and get it right, but with the pins you always get it right.

Maybe someone else can come in on this, but I think the answer to your question is "Yes", you can get it on wrong without the pins.

Agreed. And any "pro" mechanic that does that should have his wrenches repossessed. :mad: The pins are ther mainly for shear load transfer, the bolts are set up strictly for tension application.