The Stovebolt Site Forums The Shop Area Engine Shop REAR BEARING LEAK On Engine

My Son and I just got done with restoring everything as far as the running gear goes on our (1940 1/2 Ton Truck). We jacked the back end up off the ground and fired up the engine. After it had run for a while we shifted it thru the gears. A little while latter we saw some oil dripping from the clutch cover. We shut the engine down and then the oil ran for a little bit then stopped. We ckecked the oil level and it was OK so we started the engine up again and the same thing happened. We are thinging it is the WICK in the rear bearing were the oil is coming from. We would like to now if we can drop the oil pan and replace the wick in the rear bearing or do we have to pull the whole drive train apart to get at the problem. Please if anyone can let us now as soon as possible. You can contact us at this Email [email protected]
****PS**** I quess we forgot to tell everyone the engine is a 216 straight 6 cylinder. This is the original engine. Waiting to Hear from everyone

Tailgate, Check out the Tech Tips section, look under engine, rear oil seal replacement.

Hy Tailgate, I think you created your own oil leak by jacking the truck up in the rear without blocking the front up so it would end up level, I think some of your transmission oil leaked out of the front bearing, there is no seal there the only thing that keeps the oil in is keeping it at the proper level, hope this helps.

3B,

As much as I respect your knowledgeable post's, I am going to disagree with you. I don't think gear lube would leak from the transmission by putting the rig in the nose down position.

It seems if this were the case, driving down a long steep grade would certainly raise havoc with the clutch, from a leaky gear lube standpoint.

I think the rear main is leaking..a quick smell of the oil slick would tell the tale.

Rumor has it that if not all the flywheel bolts were installed, a path exists between the rear main cavity and the outside of the engine.

I would guess that the information in the Tech Tip answered all of Tailgates's question. I will add that I have replaced several rear main seals (rope type) with the engine in the rig..it isn't the most fun I have ever had, but it certainly can be done effectively.

I think if the mains are badly worn and loose, the fix will not be permanent.

Stuart

atomarc wrote:

"Rumor has it that if not all the flywheel bolts were installed, a path exists between the rear main cavity and the outside of the engine."

Not a rumor! This can happen and I am living proof it can! I would FIRST check the flywheel and be sure ALL of the bolt holes are closed with a bolt. The oil can come out of the of the clutch or flywheel cover!

Joe

Joe,

I know that this can happen..I was taking liberty with my prose.

Stuart

Hy atomarc, I was only offering a suggestion of somewhere else to look given all the facts in the post, and I have seen this before when a transmission has been over filled, that is why we only fill to the bottom of the plug on a level surface. Tailgates post said they had just completed restoring the running gear, so I assumed [and we all know what happwns when we do that] that a new seal had been installed correctly. By the way does the replacement neoprene seal fit the 216s if my memory is right I think it does.

If you have all bolts in the fly wheel and the seal is correct installed abnd not lkeaking (the neoprene seal fits 216 but will not seal. It only works on 55 or 56 engines up)your crankshaft may needs balancing. Been there....

but check all other posibyllities first. This is a verry rare condition.

Frank

Hello To Everyone That Replied to My Leaky Rear Seal. I Dropped The Oil Pan And Then The Rear Main Cap. I Removed The Wick In The Rear Cap And Installed The New One. But I Did Not Find A Good Way To Get The Wick Out Of The Block So We Did Not Put The New One In. I And My Son Dissided To Remove One Of The Two Shims On Each Side Of The Main Cap And Put It All Back Together. We Put It Back Up On Jack Stands And Ran It Like Before And No Leaks. Does Anyone Think I Will Have A Problem With This Down The Road. It Seems To Have Taken Care Of My Problem And The Engine Seems To Run Just Fine.

Removing the shims may hurt your crank and bearings.
I would put it back on and the wick out of the block.

For peace of mind and the wick in the block search for "Chinese Finger Torture Tool" (no joke).

According to an informative source who worked on these motors in a GM dealership, what you performed was what they used to, do to the letter.

First was to adjust the rear main bearing itself because that would stem the flow soemwhat. By the procedure in the manual, if you removed one shim from each side and the motor was not too tight, this adjustment is just fine and needed.

For the seal, it was standard procedure to replace the bottom only because you can run into real difficulty trying to get the old one out of the top, with the crankshaft in place.

Congratualtions on your success. as far as whether it will start leaking again, there is no reason to worry about that. I would just keep an eye on it just like you would the rest of the motor.

The way we were taught to check main and rod bearing clearances at the Chevrolet plants in Saginaw was to use plastigage. Very accurate and still available. The instructions are on the box.

http://www.hastingsmfg.com/Tools/plastigage.htm

Beat me to it fredstev. No problem removing the shims if you still have adaquate clearance

If you read the service manual, you will find a detailed procedure for adjusting the bearings. The procedure relies on removing shims until there is interference and then replacing one. Plastigauge works really well on a new assembly but it is not that great for a partially worn engine.

Well, yeah, maybe. If you have tapered or grooved bearings or journals, plastigage isn't too accurate. It's been a LONG time since I've messed with the babbit bearing system, but do use a micrometer to check the thickness of the shims. I seem to recall that they came .001, .002 and .003 and there just may have been .0015 shims available.

At any rate, I would "unshim" about .001 at a time. If you DO use the plastigage, don't rotate the crank after you put it in, just torque down, then remove the cap.

Real GM mechanics, please comment here.

Hello to everyone that replied to my question. This will ease my mined about what we have tried. We will keep an Eye on the engine to see if anything changes. *****Thanks again******

fredstev,
on those 216s, they came with brass and steel shims. The steel shims were .001" and the brass one were .002". If I remember correctly, there were one brass and two steel shims on each cap when they were new. Some of the literature specifies the bearing wear limit as .004".

You're right - I'd forgotten about the brass shims. I called a geezer buddy of mine, he said that the blued steel ones were .003 and for new assembly only. He didn't remember any .0015 shims.

The plant next door to where I worked in the mid-sixties was "service parts". They had one assembly line that we supplied castings for, the "5 main bearing" engine, AKA the service six. This was our old friend, the 235 CID "blue flame" six. That engine went in every delivery truck known to man.