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old 6.2: which oil to free up stuck rings?

Discussion in '1982-Present GM Diesel' started by Steve_87K5, Sep 23, 2005.

  1. Steve_87K5

    Steve_87K5 1/2 ton status

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    This old '82 6.2 has been sitting for several years outside, under the hood of a Suburban. The compression is equal on all cyls at about 120 PSI.

    I pulled it and have it on a stand, and have shot some Marvel Mystery oil
    into the glow plug holes because I think the rings have set up.
    What else could it be? The guy I got it from said it was low miles and
    ran fine before.

    Right now I am on my 2nd soak with MM oil.

    1. Is there a better oil to squirt in to unseize rings?
    The 2 syringes in the photo are "flavor injectors" I found at supermarket.
    30 ml capacity with graduations. Perfect for knowing how much oil you
    have put in.

    2. how long should I let the MM oil (or something else??)
    sit in there? The first time I let plain
    30 weight sit sit for only a few hours. This did not improve PSI.

    3. what should the cranking RPM be to get a proper PSI reading? I tested
    with glow plugs out. Oil I added, squirted out all over the place from the glow plug holes.

    stuck rings.jpg
     
  2. sweetk30

    sweetk30 professional hooker Premium Member

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    pb blaster works wonders.
     
  3. yunit

    yunit 1/2 ton status

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    Get yourself some marine fogging oil; stuff is awesome. Try to get it in a spray can, it will foam up coating the cylinder walls and will help breakdown any kind of rust that may be in the cylinders.
     
  4. Steve_87K5

    Steve_87K5 1/2 ton status

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    Called Advance Auto, they have PB Blaster in gallon cans, nonaerosol for just under $20.

    Will try this PB, and also see if I can find the fogging oil. Do you recall
    the trade name for the fogging oil?
     
  5. arveetek

    arveetek 1/2 ton status

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    Since the engine is already on a stand, I would highly suggest that you go ahead and tear the engine apart to see what the problem might be. If the engine was in a vehicle that you were wanting to run right away, I would try unsticking the rings, but you might as well tear it down, hone the cylinders (which are probably rusty), install new rings and bearings, install new head gaskets, and then you're set to go, assuming you don't find any other major problems.

    Casey
     
  6. Steve_87K5

    Steve_87K5 1/2 ton status

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    You are right.

    But... I am going to use some penetrating oil
    for a week or so, and retest.
    Then decide if a complete T&I is called for.

    It is a GM reman engine, from the original owner, he says
    w/less than 20k on the engine.

    It's one of the old blocks which originally had red paint.
    It's also J code.
     
  7. diesel4me

    diesel4me 1 ton status Premium Member

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    Marvel oil works ok..

    We used Marvel Mystery Oil on a lot of the antique cars gas engines that sat for years in the boneyard to free up stuck valves and rings..but oil does not always penatrate deeply enough, or loosen baked on carbon--a few motors we tried using laquer thinner--it lossened the rings up better than oil did,but we also had to drain and flush out the crankcase before attempting to fire the motor up..

    We found nothing frees them up better than getting them running!--some motors had such low compression they refused to start--we'd dump oil down the intake while it was cranking over good--that usually built up enough of a "seal" to allow it to start-(also would help knock a stuck valve closed sometimes)..you dont need a lot of oil--but a diesel might "run away" on the oil until it burns off!--a rude awakening for a low mileage motor...might not be a good idea on a diesel engine..but if you could get it fired up and let it run awhile,that will probably free the rings up better than soaking them with anything will...wont hurt to soak it though.. :crazy: be prepared to fog out the nieghborhood once it starts!.. :haha:
     
  8. imiceman44

    imiceman44 1 ton status

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    I think he will have a problem starting it with 120 PSI.
    Mine were just under 300PSI and the engine wouldn't start.
    I am sure with a little coersion it might start with me but at 120 there isn't enough pressure to ignite.
    :(
     
  9. crawlink5

    crawlink5 1/2 ton status

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    try a non-polar solvent something like heptane (if you can get it), it dissolves petoleum products well. Works good on tar. Maybe spray can carb cleaner.

    Or try Kroil.

    Acetone won't work. It is polar like water.

    If you install the engine without taking it apart, you'll always wonder if you still have that problem.

    At least pull the pan to let this stuff drain.

    A few gaskets, a set of rings, and a days work and it'd be done right. A stuck ring WILL ruin your cylinder wall. They are made to float.
     

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