Main seal Leaking.. looking for causes

Discussion in 'Small Block Tech' started by apachepatmanfx, Sep 12, 2018.

  1. apachepatmanfx

    apachepatmanfx Well-Known Member

    I have a main seal leaking. the 72 buick 350 has 60,000 miles on it. Never Raced, maybe punched it here and there. The car has been sitting and started now and then for the past 5-6 years. I assumed that the seal may have dried up.

    The mechanic says there may be a deeper issue than just the main seal. I just wanted to run this buy you guys.

    I really don't want to spend 1900 for a mainseal and bearings. A friend said he would do it for $800.
  2. BYoung

    BYoung Stage me

    Be sure to use the TA seal. A leaking rear main seal doesn't necessarily mean there are any other problems. The rope seals get old and dry up. Had it replaced on my 72 GS350 and it is now dry as a bone.
  3. 1970 STAGE 1

    1970 STAGE 1 Well-Known Member

    I replaced my rear main for 100 dollars in parts. If you had a mechanic type friend it is not a bad job to do yourself. Torque wrench and a way to lift the front of the engine are your only non normal things that you may not have.
  4. buick64203

    buick64203 Mopar or no car Staff Member

    800?? American dollars? For what exactly? to replace the seal??
  5. apachepatmanfx

    apachepatmanfx Well-Known Member

    Yes. How much should I be paying? If we weren't in the process of moving I would do it myself, but I don't want to be "rushed." Mechanic quoted $1900, and a friend said $800.

    The mechanic (reputable racing shop) on the phone was either trying to upsell me or fear monger. The work done to my engine is in my sig. The car was well maintained, never abused, but now and then I would open it up on the highway and (as a stupid teenager).

    The crankshaft was ground and polished by the previous owner, i would assume the replaced the bearings while they were in there, but not confirmed. At 60,000 miles this should not even be an issue.
  6. pbr400

    pbr400 68GS400

    I bet your problem started after the rebuild. Rope seals used to have asbestos fibers and were fairly durable. New ones don’t and that makes them more prone to leaks, so use the T/A neoprene instead. Also, unless you’ve run it out of oil you shouldn’t have any other problems (depending on the rate of leak, just park over dirt, check you oil regularly, and wait for a better price). Shop around!
  7. telriv

    telriv Well-Known Member

    I've done this MANY times & it normally works. Others I've told have tried it also. Some with success & some with out. Put in a pint of Dot 3 brake fluid & run it. Especially if the car has been sitting & NOT driven on a regular basis.
    What can you lose the cost of a pint of brake fluid???
    Ask Nick Servo if it works or not. He'll tell you.

    Tom T.
    300sbb_overkill likes this.
  8. buick64203

    buick64203 Mopar or no car Staff Member

    Sounds like a lot to me. And just out of morbid curiosity, how bad is it leaking?
  9. 64 skylark mike

    64 skylark mike Well-Known Member

    T/A seal kit is $16.95 plus shipping. I replaced mine with their kit, worked good and not too difficult. Did the work with engine in the car, parked in the carport on jack stands. One afternoon. Both prices seem high to me.
  10. sean Buick 76

    sean Buick 76 Buick Nut Staff Member

    Drive it for 200 miles keeping an eagle eye on the oil level and likely it will swell up and seal up okay.
  11. MrSony

    MrSony Well-Known Member

    Buy a ford 460 rear main seal from the parts store for $10, use gbs of rtv in place of side seals. Thin smear on the mating surfaces from cap to block install seal offset so it will push together when installed. No leaks here. Buy a pan gasket as well. Oil pickup tube gasket (football shaped) while you're in there. No rtv on the pickup gasket, install dry. Tighten with 1/4 ratchet just past snug.
  12. buick64203

    buick64203 Mopar or no car Staff Member

    This is good advice. And the best part is that it doesn't cost $800:D
  13. 64 skylark mike

    64 skylark mike Well-Known Member

    Yeah, Ford 460 seal is exactly the same, but T/A kit comes with the wedges and pins for the side seal. First time I bought this seal from NAPA, and it was $27 without side seal stuff. I didn't price it at Auto Zone or O'Reilly's though.
  14. sean Buick 76

    sean Buick 76 Buick Nut Staff Member

    My 75 regal leaked so bad out of the rear main when I bought it that it was unable to be driven... I drove it around for a few hours, checking the oil level and topping it up as needed. Next thing I knew it had stopped leaking... never leaked anymore after that... it had sat for 10 years prior to me buying it.
    BYoung likes this.
  15. gstewart

    gstewart Well-Known Member

    Dude wants to pull the motor + trans. The most sensible way to then replace rear main seal & front seal & maybe the rear cam plug. Been there and done all that, with help from a couple of friends.
    Last edited: Sep 18, 2018
  16. sean Buick 76

    sean Buick 76 Buick Nut Staff Member

    True yes I know I pulled the engine to do my main rear... was fun.
  17. jay3000

    jay3000 Well-Known Member

    So, do the math for me. Assume this is a working shop that pays its' employees.
  18. buick64203

    buick64203 Mopar or no car Staff Member

    The book gives you 2.9 hours. And if you plastigage the bearing, its an extra .4
  19. jay3000

    jay3000 Well-Known Member

    :D Good luck with that..
  20. buick64203

    buick64203 Mopar or no car Staff Member

    Even if the mechanic drags his feet and takes an extra 2 hours, at $100/hr, that's still $500

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