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Thread: Cracked Head

  1. #1
    Join Date
    Apr 2011
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    12

    Default Cracked Head

    My 6.5 ran hot (multiple times) so I replaced the water pump. Not only did it run hot again, I could get water to flow into the engine by squeezing the Upper Coolant Hose. I was concerned about locking up the engine so I let it sit. Unfortunately, I have let it sit for over a year and now I am ready to do what I need to do to get it going.

    Hoping someone can give me some advise on what to check next and keep from locking up the engine. I assume I need to change the oil/filter, pull the glow plugs, and crank the engine over by hand? Trying to ensure that the coolant is going into the engine through the head and not where I installed the new water pump.

    If I have to do a head job, just want to verify it's a head/head gasket before pulling all of that out, etc.

    Any help will be appreciated.
    95' GMC C3500 6.5L Dually 5" Stack Exhaust 4" Aero Exhaust Turbine 185k miles

  2. #2
    Join Date
    Feb 2007
    Posts
    2,891

    Default

    I assume by water flowing into the engine, you mean into a cylinder. I is probably already seized. If you meant into the oil, then that will be the water pump job, failure. Is or was the oil milky coloured. Either problem, the coolant needs to be drained and the engine run for a minute, of course changing the oil if water is in it. That is if you are not going to fix it now. To check for which head has a problem, remove the serpentine belt and remove the thermostat cross over. Now you can see the coolant in each head, have someone crank the engine over, or start it, and see if bubbles come out of the coolant.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, 3.73 diff, 16 mpg
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, since 1992.

  3. #3
    Join Date
    Apr 2011
    Posts
    12

    Default

    Thanks for your quick response. I thought I would get an email when someone responded so now I know I have to keep checking back.

    The engine was running fine when I let it sit. It just kept over heating. I did take the water out of it over the winter because it was pure water with no antifreeze, etc.

    I just want to be clear. Are you saying to run the engine with no antifreeze and no thermostat crossover? My fear then is damaging the brand new water pump?
    95' GMC C3500 6.5L Dually 5" Stack Exhaust 4" Aero Exhaust Turbine 185k miles

  4. #4
    Join Date
    Feb 2007
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    2,891

    Default

    I am sill not clear on whether water gets into the oil or a cylinder when you squeeze the radiator hose. But to answer your question, remove the crossover coolant pipe and the serpentine belt, to stop the water pump from blowing the water out, and fill the block with water. Now running the engine or perhaps just cranking it will show bubbles coming from one of the heads, if there is a crack or blown head gasket.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, 3.73 diff, 16 mpg
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, since 1992.

  5. #5
    Join Date
    Apr 2011
    Posts
    12

    Default

    Thanks Grancito, I could only hear the water and see it on the dipstick so I guess I would have to say getting into the oil. I had no way of knowing if it was getting into the cylinder and that is why I stopped immediately.

    I better understand what you are saying now. The pump won't be harmed because it won't be turning. Gotcha. I will get back to it in a week or so and circle back. I can't thank you enough for all of your help.
    95' GMC C3500 6.5L Dually 5" Stack Exhaust 4" Aero Exhaust Turbine 185k miles

  6. #6
    Join Date
    Feb 2007
    Posts
    2,891

    Default

    Something must have gone wrong with the assembling of the water pump, I can't imagine a head gasket blown that bad. There will be water through the bearings and lifters, and likely corrosion after sitting so long. If it had a blown head gasket that bad, the engine would run rough and probably blow the dipstick out and blow the coolant out. Did you put all of the bolts in the water pump back plate?
    Last edited by grancito; 05-21-2019 at 06:06 PM.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, 3.73 diff, 16 mpg
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, since 1992.

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