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Rear Main Seal Rubber Dowel Alternative

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Chris Breedlove

Farmall Cub
Joined
Sep 11, 2014
Messages
110
Points
18
Location
Canton, MA
Replacing the rear main seal. This is the second time. I'm using a speedi sleeve on the crankshaft, and the rubber type lip seal, not the Teflon one. I noticed that the rubber dolls I put in their previously, had climbed up inside the block at least a quarter of an inch. This may be the source of my leak. Other then replacing the rubber dolls again, or squirting RTV up in the holes, why can't I drill, tap, and plug these holes? Any reasons not to? Thanks!
 

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Dana Strong

Lives in an IH Dealership
Joined
Apr 4, 2008
Messages
6,471
Points
113
Location
Sunnyvale, Ca.
Replacing the rear main seal. This is the second time. I'm using a speedi sleeve on the crankshaft, and the rubber type lip seal, not the Teflon one. I noticed that the rubber dolls I put in their previously, had climbed up inside the block at least a quarter of an inch. This may be the source of my leak. Other then replacing the rubber dolls again, or squirting RTV up in the holes, why can't I drill, tap, and plug these holes? Any reasons not to? Thanks!
I assume you're speaking of the two machined holes, one on each side of the insert and at its junction with the block. I've never heard the side seals called dolls, but that aside, the rubber plugs are supposed to adsorb oil and expand to fully seal the hole. The bottom surface should fit against the oil pan, perhaps sticking out a bit after expanding.
How would drilling, tapping and screwing in something(?) better seal those holes, leave alone possibly cause other problems?
Assuming the rubber plugs are still installed, why not try to blow air through the junction to satisfy yourself that those junctions are still sealed?
I wouldn't remove either the plugs or the bearing insert; I'd be sure the crank sleeve was properly positioned, that the new crank seal fit over it properly and wasn't damaged during installation and that it had a film of oil on the contact surface before running the engine.
Did you install the 4 screws when pulling the old seal shown in the picture? It didn't come with holes for that purpose, did it?
 

Greg R

Lives in an IH Dealership
Joined
Mar 23, 2002
Messages
5,364
Points
113
Location
Lebanon, OR
I drill, tap, and plug these holes?

No. The rear main bearing cap along it's vertical edge is fairly loose in the block most of the way. The bottom 1/2" inch or so and the mating surface to the block is tight, almost an interference fit. The side plugs stop leakage along those edges between the bearing cap and block, particularly the "loosey goosey" part.

Add to that, the amount of material in the cap between the side seal chamber and the main seal bore is very very small. It's almost as if the seal bore is not directly centered in the cap it self.

15 years ago I put a very light coat of Right Stuff on the plugs and it slid in further than the 1st time I did the job. No leakage since though it will probably require removing the bearing cap, (with the tool), to clean it out properly if it ever needs replacing.
 

Chris Breedlove

Farmall Cub
Joined
Sep 11, 2014
Messages
110
Points
18
Location
Canton, MA
I assume you're speaking of the two machined holes, one on each side of the insert and at its junction with the block. I've never heard the side seals called dolls, but that aside, the rubber plugs are supposed to adsorb oil and expand to fully seal the hole. The bottom surface should fit against the oil pan, perhaps sticking out a bit after expanding.
How would drilling, tapping and screwing in something(?) better seal those holes, leave alone possibly cause other problems?
Assuming the rubber plugs are still installed, why not try to blow air through the junction to satisfy yourself that those junctions are still sealed?
I wouldn't remove either the plugs or the bearing insert; I'd be sure the crank sleeve was properly positioned, that the new crank seal fit over it properly and wasn't damaged during installation and that it had a film of oil on the contact surface before running the engine.
Did you install the 4 screws when pulling the old seal shown in the picture? It didn't come with holes for that purpose, did it?
The seal is already removed. I put the screws in it to get a good grip on it with a slide hammer. I don't understand why the holes are there in the first place. The rubber dowels, or side seals, seal those holes and that's there only function, what difference would it make to tap the holes and put plugs in them? Threaded plugs mean no leaks. Why should I not thread the holes and put plugs in them?
 

Chris Breedlove

Farmall Cub
Joined
Sep 11, 2014
Messages
110
Points
18
Location
Canton, MA
No. The rear main bearing cap along it's vertical edge is fairly loose in the block most of the way. The bottom 1/2" inch or so and the mating surface to the block is tight, almost an interference fit. The side plugs stop leakage along those edges between the bearing cap and block, particularly the "loosey goosey" part.

Add to that, the amount of material in the cap between the side seal chamber and the main seal bore is very very small. It's almost as if the seal bore is not directly centered in the cap it self.

15 years ago I put a very light coat of Right Stuff on the plugs and it slid in further than the 1st time I did the job. No leakage since though it will probably require removing the bearing cap, (with the tool), to clean it out properly if it ever needs replacing.
Than you, I understand the reasoning here. Rubber dowels/ side seals it is then. This time though, I'll put RTV on mine.
 

jeff campbell

Moderator
Staff member
Joined
Jan 8, 2003
Messages
16,614
Points
113
Location
lima,ohio
The seal is already removed. I put the screws in it to get a good grip on it with a slide hammer. I don't understand why the holes are there in the first place. The rubber dowels, or side seals, seal those holes and that's there only function, what difference would it make to tap the holes and put plugs in them? Threaded plugs mean no leaks. Why should I not thread the holes and put plugs in them?
Not designed to function properly if plugged.with threaded plugs or screws. No need for re-invention of a lifelong project.
 

J.J.

Lives in an IH Dealership
Joined
Dec 14, 2003
Messages
7,014
Points
113
Location
Castalian Springs, TN
I never put those back in, clean it up with carb cleaner and squirt some of "the good stuff" up in there until it oozes out of the cracks from the top down. None of mine leak.

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JJ in TN
 

Greg R

Lives in an IH Dealership
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Mar 23, 2002
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5,364
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113
Location
Lebanon, OR
Going on the look of what extruded out, gotta wonder what went IN the crankcase or the cap's drain groove for that matter.
 
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