Rear Main Seal Rubber Dowel Alternative

Discussion in 'General IH Tech' started by Chris Breedlove, Feb 14, 2020.


  1. Chris Breedlove

    Chris Breedlove Farmall Cub

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    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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  2. winchested

    winchested Y-Block King

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    Because the dowels are in the split of the main bearing cap. I rtv'd mine in and I haven't had a drop from mine.
     
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  3. Chris Breedlove

    Chris Breedlove Farmall Cub

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    You mean you coated yours in RTV then stabbed them in? Did you cut them flush or leave a little past flush?
     
  4. Dana Strong

    Dana Strong Lives in an IH Dealership

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    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?
     
  5. Greg R

    Greg R Lives in an IH Dealership

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    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.
     
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  6. Chris Breedlove

    Chris Breedlove Farmall Cub

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    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?
     
  7. Chris Breedlove

    Chris Breedlove Farmall Cub

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    Than you, I understand the reasoning here. Rubber dowels/ side seals it is then. This time though, I'll put RTV on mine.
     
  8. Greg R

    Greg R Lives in an IH Dealership

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    Very little, just a dab to light coat.
     
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  9. jeff campbell

    jeff campbell Lives in an IH Dealership

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    Not designed to function properly if plugged.with threaded plugs or screws. No need for re-invention of a lifelong project.
     
  10. mallen

    mallen Y-Block King

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    99 times out of 100 someone's "better" idea when repairing something makes it t worse or screws if up.completely.
     

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