The Stovebolt Site Forums The Shop Area Engine Shop 216 Rear Main Seal Replacement ?

My '38 is leaking oil like crazy - about one drop every 3 seconds drips from the lower clutch cover when the engine is running.

So, my question is: Can I replace the rear main seal on this 216 without pulling the engine ? I can't find a nice picture of how it all goes together so I don't even know what surfaces the seal touches, but I'm assuming I can just remove the clutch and flywheel and get to the rear main seal. Does anything else need to come off ? Oil pan ? Crankshaft (I hope not !). Apparently I'll be using the "original rope type" seal, as the neoprene replacements are not listed as fitting the pre-1941 216's.

Thanks in advance to all the 216 gurus out there.

Alex Meade

If you really have a 1938 engine it will not have a rear seal, they only had a slinger. Are you sure it is not the pan gasket? If it is coming from the crank it would help to pull some main bearing shims to slow down the oil leaking out of the bearing.

So how effective is the slinger ? Is it actually better than what followed?

Pre '68 Dave:

Well, at least I know I'm talking to the right folks about this ! So, the numbers on the block of my 216 decode to being made in 1939. Does this change the situation any, or did the '39 also not have a rear main ?

Thanks, again !

Alex

Pre '68 Dave,

I should have answered your other question: I'm not sure that the leak is not coming from the pan gasket - the only observation is a steady drip from hole at the bottom of the clutch cover when the engine is running.

Thanks again.

Alex

That is usually a pretty good sign that it is a rear main seal leak, assuming that you have a rear main seal. As you will see in the tech post, you have to remove the pan for starters, to replace it. I tried the method in the post and I could not get the old one out. I read about another method of removing the tranny, ( I would think clutch and flywheel) all the main bearing caps (that means the front cover too) and pulling the crank down some as it is still suspended by the rods. I think that would work for sure.

1940 was the first year 216s got a rear seal. A 1940 can easily be distinguished from a 39 by the oil distributor on the drivers side. 1940 was the first year to use the kidney bean shaped three screw cover.

Truckernix -
Thanks for the hints - I was assuming that the tech tip began with the assumption that the trans, clutch and flywheel were already out, so it would be pretty nice to not have to remove them. Seems like the main thing I have to figure out is whether or not I actually have a main seal at all.
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Pre '68 Dave,

Based on your description, I think it's still probable that I'm pre-1940. The oil distributor only has two bolts holding it to the block. If it helps any, the casting numbers on the block look like this:

GM
888941
21

Any of the "8"s could be "3"s. I've been told in the past that this indicates a 1939.

So, assuming that this is indeed a 1939 engine without a rear main seal, it sounds like the recommendations are to pull the pan, maybe tighten up the rear main bearing by removing shims, and reseal the pan. Are there any other sources that could cause the leak as described ?

Thanks again - this is an awesome forum.

Alex

I would say that 75% of the time when someone says there main seal is lealing it is the valve cover leaking. Oil will run down the back of the engine into the flywheel cover which makes it look like a main seal leak.

Pre '68 Dave,

That's good to know. Maybe I'll be one of the "lucky 75%".

One other thing occurred to me: maybe I've got too much oil in the crankcase. I'll obviously need to drain the oil anyway to replace the pan gasket, so I'll measure what comes out. Maybe I have a too-short dipstick !

In any case, when I take the pan off, the '38 shop manual tells me that I should do a number things: check and adjust the dipper heights, check the depth of the oil nozzles, aim the oil nozzles, and check the trough depths. Sounds reasonable, except they are all specified in terms of special gauges - no numbers are given.

So, I assume I should just cross my fingers and bolt it all back together, under the premise that it's working now, so it's probably OK. Any advice in this area ?

Thanks once again.

Alex

I would be slapping it back on without " fixin stuff that is not broke!!". The one exception here would be shim adjustments of the rear main bearing. It would be a good idea to look at that.

Truckernix,

You folks are great !

Now, about that rear main bearing adjustment: My shop manual talks about how to shim each bearing until the crank turns freely by hand, but the procedure assumes no other bearing caps are in place and the connecting rods aren't there either. No clearance numbers are given. Obviously with the crank still attached to the conn. rods and the other main bearings, this method won't work. So, I'd jump to Plastigage or some other technique to set the clearance. What's the recommended clearance for the rear main bearing ?

Thanks !

Alex

I would agree that the dippers and troughs should be set ok if it is working now. Bearing clearance is .001-.003". If you use Plastigage support the crank with a bottle jack to hold it against the top bearing.

Pre '68 Dave,

One last question, as this is the first time I've been inside this engine: Where can I find torque specs for the bolts ? Clearly the ones I'll be looking for are the pan bolts and the bearing cap bolts, but in general, is there a source for this information. Again, the shop manual for my '38 doesn't mention torques.

Thanks once more !

Alex

Amen on the plastigage!!! I followed the non-pg method in the manual and ended up with a seized rear bearing after removing shims to stop seal leak in my '52.

The reason you don't find the torque specs in your manual is that torque wrenches weren't invented yet:)
The torque for main bearings is 105 ft lbs. The torque for the rods is 40 ft lbs.

What I found with plastigauge on an old engine is that because the crank and bearings do not wear in a perfectly even pattern, you can get readings that look right but there is great interference. I found that the shop method worked best for me. You will find that the motor will turn quite easily and when you don't have enough clearance, it will make a big difference. Of course, you want to remove the sparkplugs so you are not fighting compression.

Yes checking rod bearings with plastiguage can be inaccurate since rod journals wear out of round. Main bearings tend to stay round as they wear so plastiguage is an acceptable method.

My impressions are more relevant to the rod bearing adjustments but I did my rods and mains by the shop method. If you want to see how easy or difficult it is to turn the motor over, remove the spark plugs and turn it over with the fan belt.

Pre '68 Dave,

OK, I just gotta ask: Where are you finding all of these valuable numbers - bolt torques and bearing clearances ?? If I ever rebuilt this 216, I'm sure there are a few more I'll want to find out.

Alex

Alex
216s and 235s use the same bolt sizes and the later shop manuals give 235 torque specs.