1955 331 V-8 upper rear main seal

[5390john]

Just to make it interesting, after 6 years of restoration and 3 weeks after winning 2 awards at the first showing, my '55 Coupe De Ville decided to have the engine's upper rear main seal fail, puking out about a cup of motor oil on the garage floor.
I'm assuming this will require removing the engine, but thought I would check and see if anyone out there had any "old mechanics" secret magic cures for replacing the seal without pulling the engine.
Anyone?
John Adams

[The Tassie Devil(le)]

I take it that the seal you are referring to is the old "dog turd" style.

How do you know it is the upper half that is leaking?

As the transmission is still attached, one simply cannot drop the crank whilst the engine is in the car.

I have always found that the best fix is to remove the engine to get the crankshaft out to give you complete access to it.

Bruce.

[Jay Friedman]

John, Bruce,

I respectfully differ.  The rear main seal, both upper and lower, can be replaced without removing the motor.  I've done it several times, to 2 '49s and a '51, both alone and along with fellow CLCer Art Gardner.  In fact, Art wrote a detailed, illustrated article on how to do it, including the only really tricky part which is trimming the new oil pan gasket.  I'd be glad to email it to you if you send me your email address at jaysfriedman@yahoo.com.  (I don't know how to post illustrations to this web site.)

To summarize, you must first remove the starter, the oil pan, oil baffle, oil pump and then the rear main bearing cap.  The key is to loosen somewhat but don't remove the screws on the four front main bearing caps so that the crankshaft drops down a few thousandths of an inch to ease upward pressure on the upper half of the old rope seal.  You then partially screw a wood screw into one side of the existing rope seal and press a brass punch (brass so you don't scratch the crankshaft journal) against the other side of the seal.  You grab the screw with a pair of pliers and pull, while pushing against the other side of the upper half of the seal with the punch, and it will come out.  You just pull the lower half of the seal out of the bearing cap.  Once both halves of the seal are out, you can easily install a new modern neoprene rubber seal available from Terrill Machine, DeLeon, Texas, which doesn't require the careful trimming necessary on a rope seal. 

[The Tassie Devil(le)]

I mustn't be holding my mouth right as I have never been able to get these out, and replaced satisfactorily.   Never had one leak when I have installed them.

Doesn't a crankshaft with the rope seal have spirally ground grooves in the crank to assist in working any escaping oil back into the engine as the crankshaft turns?

I have seen these on many cranks with the rope seal.

Whereas the neoprene seal requires a completely smooth seal surface.

Bruce.

[5390john]

Hi Jay:
Thank you for your response, I very much appreciate it.
My e-mail is john@logo-products.com
I would love to receive the article you mention. If this works, I'll owe you one big time........maybe two!!
John Adams

PS, Marilyn would also appreciate it, see attached

[The Tassie Devil(le)]

Please let us know how you went, including the replacement of the replacement seal.

If you do get in a replacement neoprene seal, make sure you put it in the right way.   As in the lip to the front.

Bruce.

[Roger Zimmermann]

Doesn't a crankshaft with the rope seal have spirally ground grooves in the crank to assist in working any escaping oil back into the engine as the crankshaft turns?

No Bruce: the crankshaft is smooth at this location. Like Jay, I replaced with success the old rope with rubber half seals. As the ceiling of my garage is low, I don't have a lift. Did all my work on the back! Sometimes it's oil raining...

[Jay Friedman]

John, I emailed you Art's article.  Hope it helps.

Bruce,  You are right in cautioning that the lip of the neoprene seal must point the correct way.  Would be a major downer to have to take everything apart again to reverse an incorrectly installed seal.  Roger is right: the crankshaft does not have spiral grooves in the crankshaft at the rear.  However, if I remember correctly it does have spirals or what looks like threads in the FRONT of the crankshaft just behind the felt seal in the timing chain cover.  When the crankshaft is turning with the motor running, the spirals "move" toward the interior of the motor, thereby "working any escaping oil back into the engine" as you wrote.  I imagine the reason is that the felt seal is not much of a seal and needs all the help it can get.  I would also guess there is not much oil pressure at that point.  Let me add that replacing the rear main seal without removing the motor can be done in a 1949-55 331 or 1956 365 motor (which is practically identical), but I have no idea if this is true of earlier or later motors.

As Roger mentioned "oil raining", it brings to mind that, as the old saying goes, someone has to do it but this is definitely a filthy job.  Even after draining the oil out of the motor before removing the oil pan (sump for Bruce), enough oil will remain in the motor that, as you remove each component, more oil will spill out and, if you are not careful, maybe all over you or your garage floor.  So, I suggest covering the area under the motor with flat pans or any other appropriate container to catch it, as well as covering yourself with whatever it takes. 

Roger, I also did this once lying on my back in my garage.  It wasn't getting down under the car that was a problem, but getting up again afterwards.

[Roger Zimmermann]

Roger, I also did this once lying on my back in my garage.  It wasn't getting down under the car that was a problem, but getting up again afterwards.

Newton saw that too with the apple! I don't know how you restore your nice '49; I did my 3 cars without a lift...

[5390john]

To All who commented, THANK YOU. I will be discussing this project with a highly regarded local shop in the next day or so, and see what they have to say. FYI, I am not too hip on doing this project myself, would much prefer to have someone who has experience do it. I think I've earned it after all the work I've put into the project!
John Adams

[Caddy Wizard]

John, Bruce,

I respectfully differ.  The rear main seal, both upper and lower, can be replaced without removing the motor.  I've done it several times, to 2 '49s and a '51, both alone and along with fellow CLCer Art Gardner.  In fact, Art wrote a detailed, illustrated article on how to do it, including the only really tricky part which is trimming the new oil pan gasket.  I'd be glad to email it to you if you send me your email address at jaysfriedman@yahoo.com.  (I don't know how to post illustrations to this web site.)

To summarize, you must first remove the starter, the oil pan, oil baffle, oil pump and then the rear main bearing cap.  The key is to loosen somewhat but don't remove the screws on the four front main bearing caps so that the crankshaft drops down a few thousandths of an inch to ease upward pressure on the upper half of the old rope seal.  You then partially screw a wood screw into one side of the existing rope seal and press a brass punch (brass so you don't scratch the crankshaft journal) against the other side of the seal.  You grab the screw with a pair of pliers and pull, while pushing against the other side of the upper half of the seal with the punch, and it will come out.  You just pull the lower half of the seal out of the bearing cap.  Once both halves of the seal are out, you can easily install a new modern neoprene rubber seal available from Terrill Machine, DeLeon, Texas, which doesn't require the careful trimming necessary on a rope seal.

Pictures of the seal installation job attached...