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Posted By Discussion Topic: Replace Rear Oil Seals -- page: 1 2     tbirdhandyman 09-13-2012 @ 1:07 PM reply profile send p.m. Member Posts: 51 Joined: Oct 2009 I am going to change out the rear crankshaft oil seals in a 59 AB block with a 4" Mercury crankshaft, and after removing the rear main cap and backing off on the front and center main caps, I cannot get the crankshaft to drop down at the rear. Is there a trick to this? I used a pry bar on the counter shaft weights, but it only turns the assemble, not lowering it for access to the top rear seal. Thanks for any help. This engine is in my '41 Mercury convertible. Robert E. Tbirdhandyman Stroker 09-13-2012 @ 2:53 PM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 The crankshaft cannot drop down "at the rear" because you have 8 connecting rods holding it in perfect alignment with the crankshaft axis. Don't force it, as you could damage the rod bearings. You must move the crankshaft exactly parallel to its' axis, which will require more than simply "backing-off" the center and front mains. tbirdhandyman 09-14-2012 @ 8:55 AM reply profile send p.m. Member Posts: 51 Joined: Oct 2009 Stroker: thanks for the reply. I backed the nuts off so only 2 turns was holding the front and middle caps, giving about 1/4" clearance that would allow the crankshaft to drop along its axis. I then rotated the crankshaft and so far, the crankshaft has not dropped. What do you suggest that will lower the crankshaft? Tbirdhandyman Stroker 09-14-2012 @ 12:09 PM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 The only times I've replaced an upper rear main seal was when I have had the engine on a stand, and the crank out of the block. I have never attempted this with the rods connected. The problems you are confronted with are due to the oil film on the upper main bearings, combined with the fact that in order to drop the crank, all 8 pistons have to slide the same amount at the same time, so you are in-effect dragging at least 32 piston rings simultaneously. I'd disconnect all the rods before I tried to separate the crank from the block. supereal 09-14-2012 @ 5:36 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 Trying to replace the rear seal with the engine in the car is not possible. You have to get clearance to remove the upper seal carrier. Stroker 09-15-2012 @ 6:10 AM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 Thanks Super. I was trying to avoid the "impossible" statement, as some people have developed impractical shortcuts that I have never personally attempted. tbirdhandyman 09-15-2012 @ 10:50 AM reply profile send p.m. Member Posts: 51 Joined: Oct 2009 Super: Thanks for jumping in on this. My block does have part #91A-6335, pot metal upper rear crank seal and I have read that this part could be bad. The rear main cap in my engine is #21A-6325, which has the lower rear crank seal (19B-3663) cast into it. This part number is not listed in either the '50's Green Book or the 39/48 Mercury chassis parts catalog. I guess that after 70 years there is no telling what parts are in these engines. The leak has gotten so bad that my wife's car was covered in oil after following me from a 50 mile car show trip. Regards, Tbirdhandyman supereal 09-15-2012 @ 12:15 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 My green book shows the number for the lower seal packing as 19B-6336, and the packing as 91A-6347. The seal carrier, 91A-6335, holds the packing. Unless it is damaged, it probably doen't need to be replaced. If you engine is leaking oil that bad, I'd also look somewhere else. I've seen oil leaks at the back of the engine from the oil pressure sender, the oilpump drive gear gasket, and from overfilling the pan. If the seal wasn't properly installed, and didn't have the ends cemented, it could leak, but it is usually a drip, rather than the gusher you mention. Any leak at the rear of the engine is hard to pin down if it runs down or through the flywheel housing. There is also a pipe plug behind the flywheel that seals tha oil gallery. If it wasn't sealed and tightened, it will leak badly. I have assumed you removed the transmission before attempting to drop the crank. The transmission pilot fits into the flywheel, preventing it from dropping. I would hope the prying on the crank hasn't damaged the pilot bearing, the clutch, or input shaft. That much leakage has probably ruined the clutch disk facing, in any case. Look at the C&G catalog online (cgfordparts.com) It shows the parts you need in Section 11. This message was edited by supereal on 9-16-12 @ 5:53 AM tbirdhandyman 09-19-2012 @ 11:20 AM reply profile send p.m. Member Posts: 51 Joined: Oct 2009 Super, I value your experience over the printed instructions I received with the GraphTite rear seal kit from C&G. They say "do not apply sealant on rope ends". Please tell what brand of sealant you use, and that is what I will use. I can't explain why I thought I could change this seal with the engine in the car, but maybe a hint would be that I am a member of the EFV-8 "80 Club". Regards, Robert E. Tbirdhandyman supereal 09-19-2012 @ 3:16 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 We use a dab of Permatex non hardening sealer. Avoid RTVsilicone, as it can cause problems if it gets into the oil stream. If the seal is correct size, it shouldn't have to be trimmed. Forcing the seal into the carrier swells it a bit, increasing its effectiveness. Be sure to check the other possibilities for leakage in my earlier post. Normally, oil doesn't gush from a rear seal. Drip, yes, that is why you can spot an old car garage from the layers of cardboard on the floor! As a certified old coot myself, I understand the drawbacks of the socalled "golden years".

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