Update: Rear main leak, Be aware!!
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Senior User
Joined: Jun 2002
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From: simpsonville USA
Update: Rear main leak, Be aware!!
Well,
This is an update on a rear main seal leak on my new rebuild that I posted awhile back.
Macguyver nailed it. It's a marine crank reverse rotation with the 45 degree slits going the other direction. I bought it off E-bay and thought nothing of it. It was the the right casting code? Does this mean I have to pull the whole crank and have it reground? Hey Macguyver, is their anyway to "Macguyver" it. This sucks!!
Well, I thought I had better put this out there so people check.
Ken
74 Bronco 351W
68 F100 390 (boatmotor
)
This is an update on a rear main seal leak on my new rebuild that I posted awhile back.
Macguyver nailed it. It's a marine crank reverse rotation with the 45 degree slits going the other direction. I bought it off E-bay and thought nothing of it. It was the the right casting code? Does this mean I have to pull the whole crank and have it reground? Hey Macguyver, is their anyway to "Macguyver" it. This sucks!!
Well, I thought I had better put this out there so people check.
Ken
74 Bronco 351W
68 F100 390 (boatmotor
)
Posting Guru
Joined: Aug 2002
Posts: 1,214
Likes: 2
From: Minneapolis, MN
Update: Rear main leak, Be aware!!
Sorry for your bad luck.
Considering there's no way to easily sleeve that area (like you can with the dampener), you're going to have to pull the crank. Short of starting over with a different crank, the seal area will have to be ground to remove any trace of the old grooves, at least where the seal lip rides. If you were running a rope seal, you might get away with putting in deeper grooves in the proper direction. Talk to your machinist. He may have run into it before and might have some suggestions.
Considering there's no way to easily sleeve that area (like you can with the dampener), you're going to have to pull the crank. Short of starting over with a different crank, the seal area will have to be ground to remove any trace of the old grooves, at least where the seal lip rides. If you were running a rope seal, you might get away with putting in deeper grooves in the proper direction. Talk to your machinist. He may have run into it before and might have some suggestions.
Thread Starter
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Senior User
Joined: Jun 2002
Posts: 119
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From: simpsonville USA
Update: Rear main leak, Be aware!!
Pulled the crank and my machinist doesn't feel he can safely grind the crank and still have it seal. He did bring up the idea of using a rope seal with the deeper grooves the right way but I nixed that idea as thats a big MAYBE. So it looks like I need another 390 crank. Anybody got one?
Ken
Ken
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Joined: Feb 2000
Posts: 5,130
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From: Brea CA
Update: Rear main leak, Be aware!!
Ken, I've heard of other people just grinding down the oil grooves until they disappear. The grooves are only needed for the rope seal. Does your machinist think the neoprene seal won't work?
Barry
Barry
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Joined: Jun 2002
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From: simpsonville USA
Update: Rear main leak, Be aware!!
Well,
That's the wrinkle. The seal surface is much smaller in width than the bearing journal and nobody that I know of has a precision grinder this small. So it looks like it needs to be done by hand. I think the machinist is worried that he will ruin it making it useless where now I may still be able to sell it. I only paid 40 bucks for it plus having it turned. It also has some pitting in the seal area as well?? I have found another crank for $100.00 bucks turned 10/10 (same as mine) and guaranteed to be straight with no cracks. So theres the choice, Do I attempt to grind it and hope it works, along with several hours of work, or bite the bullit and do it once with a crank I know will work and try to recoup a few bucks?? It's a s***sandwich anyway I look at it. 
All ideas are welcome, thanks
Ken
That's the wrinkle. The seal surface is much smaller in width than the bearing journal and nobody that I know of has a precision grinder this small. So it looks like it needs to be done by hand. I think the machinist is worried that he will ruin it making it useless where now I may still be able to sell it. I only paid 40 bucks for it plus having it turned. It also has some pitting in the seal area as well?? I have found another crank for $100.00 bucks turned 10/10 (same as mine) and guaranteed to be straight with no cracks. So theres the choice, Do I attempt to grind it and hope it works, along with several hours of work, or bite the bullit and do it once with a crank I know will work and try to recoup a few bucks?? It's a s***sandwich anyway I look at it.
All ideas are welcome, thanks
Ken
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Senior User
Joined: Nov 2001
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From: Western NC
Update: Rear main leak, Be aware!!
Simple choice from my view...go with the $100 good crank. Anything I could think of would certainly cost much more than that.
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