Rear main seal failure at 50 miles

Discussion in 'Small Block Tech' started by vonhef, Aug 24, 2019.

  1. vonhef

    vonhef Well-Known Member

    With around 50 miles on my engine, the rear main seal failed. It looks like the block half has over heated. The bearing cap side did not look it had failed. Crank looks perfect. I an unsure what has caused this failure. Has anyone seen this before?


  2. TrunkMonkey

    TrunkMonkey Well-Known Member

    Did you (or builder) check crank endplay?

    Overheating failure on the block side would indicate a crank too far forward and the back of the flywheel flange on the crank pressing against the seal.

    Improper sizing of the thrust bearing would be one cause.
  3. vonhef

    vonhef Well-Known Member

    Good suggestion, I just checked the end play and it reads .009”.

    here is a photo of the rear flange:

    Last edited: Aug 24, 2019
  4. telriv

    telriv Well-Known Member

    Not properly lubed upon assembly.
    alec296 likes this.
  5. alec296

    alec296 i need another buick

    I would say lube also.
  6. vonhef

    vonhef Well-Known Member

    I hope it was just lube issue. That means I can install a new one and solve the problem
  7. alec296

    alec296 i need another buick

    Vasoline on top piece. Personal i still use rope seal. Since most kits still come with it.
    docgsx likes this.
  8. telriv

    telriv Well-Known Member

    As far as I'm concerned Vasoline doesn't have the proper lubing characteristics to properly lubricate the rear seal upon start-up. Use oil or some other type of assembly lube.
    300sbb_overkill likes this.
  9. alec296

    alec296 i need another buick

    I would use something thicker then oil. It takes time for oil to get there to lube the seal. You don’t want something thats gonna burn off. Atleast a grease will stick to the seal longer.
  10. TrunkMonkey

    TrunkMonkey Well-Known Member

    I failed reading comprehension on this one.

    My take was the front (block side) was damaged, but not the back (flexplate side).
  11. vonhef

    vonhef Well-Known Member

    there is Lubriplate on the new one.
  12. bigtorque5

    bigtorque5 Well-Known Member

    dont use grease,doesnt dissolve in oil,a few engs i redid for ppl packed the oil pump with grease,never primed
  13. alec296

    alec296 i need another buick

    Thats hard to believe. I have done many fleet gas and Diesel engines with lubriplate. Never had a problem with prime or it dissolving once oil was hot.
  14. Mark Demko

    Mark Demko Well-Known Member

    I smear some 90 weight gear oil on 'em
    alec296 likes this.
  15. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    I usually use wheel bearing grease, never had a rear main seal fail. And if the rope seal serrations on the crank's seal surface weren't touched up(ground off) while the crank was being reground(if it was) the grease would block the oil from running through the rope seal serrations(for a little while anyway).

    It will take a long time for the WBG to melt off from hot oil and the seal doesn't move so it won't get slung off. It doesn't run off from where it is installed and can handle a whole lot of heat if the oil takes a long time to make it to the seal area. It doesn't take much either so don't get carried away if you decide to use it, just a thin layer on the area where the crank will contact the seal.

    Very important, make sure the seal isn't installed backwards.
    alec296 likes this.
  16. hugger

    hugger Well-Known Member

    Lubriplate is my go-to also
    alec296 likes this.
  17. Mart

    Mart Gold level member

    Was it an old stock, dried up seal that was rock hard? Or a new fresh pliable one?

    Lubriplate, EOS, or CMD hold their lube properties well.
    alec296 likes this.
  18. Schurkey

    Schurkey Silver Level contributor

    Does the crankshaft have rope-seal style embossings on it? I've dealt with several older V-8 engines where the crank has been embossed with a series of grooves designed to pull oil out of a rope-type seal, and it's so aggressive that it tears a neoprene lip-type seal.

    The journal where the seal rides looks like " ////////////////////////////////// " all the way around.

    If so, you'll want to polish the embossing so it's less aggressive. You'll never get the embossing removed totally, and if you did the journal would be undersize. You can emery-cloth some of the aggressiveness out of it, though.

    Is this seal intended for Buick engines? Or is it re-purposed from some other application?
  19. vonhef

    vonhef Well-Known Member

    It was a new seal that failed. Only one half failed.... so I must have lubed one and not the other
  20. vonhef

    vonhef Well-Known Member

    It does have the markes you describe, but they were polished by my machine shop. I also bought my seal from TA for the intended engine.

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