Water in oil - How do you test for an internally cracked engine block. GM straight 6

Discussion in 'Gas Engines' started by 73tomsawyer, Oct 20, 2010.

  1. 73tomsawyer
    Joined: Aug 2010
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    73tomsawyer Junior Member

    My straight 6 runs good, but I am getting water in the engine oil. How do I check for leaks in the block?
     
  2. wardd
    Joined: Apr 2009
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    wardd Senior Member

    pressurize the cylinders?
     
  3. 73tomsawyer
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    73tomsawyer Junior Member

    I checked the pressure of the cylinders all around 150, which I believe is right on with the age of engine. Specifically the engine is a 1973 GM 4.1 liter straight 6. Used in Chevy C-10 trucks.
     
  4. troy2000
    Joined: Nov 2009
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    troy2000 Senior Member

    A more likely culprit is your head gasket; that's a lot more common than a cracked head or block.

    It also might just be condensation, especially if you make short trips -- or if your scavenger hose is blocked.
     
  5. 73tomsawyer
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    73tomsawyer Junior Member

    I have replaced the cylinder head and head gasket with brand new ones.
     
  6. dinoa
    Joined: Oct 2007
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    dinoa Senior Member

    If you have an oil cooler check it too.

    Dino
     
  7. 73tomsawyer
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    73tomsawyer Junior Member

    I am almost positive this engine does not have an oil cooler, although I am not exactly sure what you would be describing. I can check if you can tell me where to look. Thanks for the ideas guys, hope to hear more!
     
  8. Petros
    Joined: Oct 2007
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    Petros Senior Member

    There is a dye you can get to put in the water to see if and where it is leaking. If it is coolant getting in your oil than you will see the dye in the water mixed with the oil. Check with auto parts stores, perhaps NAPA, might have such a dye.

    You also might put some stop-leak in the coolant, it will fix, at least temporarily, and small cracks or leaky gaskets that allow coolant into the oil. The stop-leak is cheap and will not harm the engine. It will tell you if it is indeed coolant getting into the oil, or just condensation.
     
  9. pistnbroke
    Joined: Jan 2009
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    pistnbroke I try

    bring each cylinder up to TDC and apply compressed air to the plug hole via an adaptor.. if you have leakage into the water jacket you will get bubbles in the water /water loss ....if its leakage from a water gallery to a oilway its most likley its in the head gasket ...was this a problem before you did the head gasket??
     
  10. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    You are needing to pressure the the water jacket and not the cylinders. Plug the the water hoses (inlets and outlets) Use a plumbing pressure test setup, which is a tire type air valve and a pressure gauge. If the pressure goes down there is a leak.
     
  11. 73tomsawyer
    Joined: Aug 2010
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    73tomsawyer Junior Member

    *THE BLOCK IS CRACKED*

    The engine runs decently, but does take on about 4 quarts of water in 3 hours of boating. How long do you think I can run it pulling skiers and such? I have a short stretch of river and could go upstream in a small area and be pretty safe with engine failure.

    Previously I was changing the oil every run, which is horrible for the environment, and not something I can live with. If I filled the engine with fresh oil once, and ran it until it died, I think I could get the most out of it.

    As posted earlier, I did install a brand new cylinder head so it could possibly be worth parting out instead. What would most likely be the first failure? Am I in any danger of a fire (the engine always ran fairly cool)? Does anyone have experience with running an engine with these problems until their just ain't nothing left? Thanks in advance, and your help is much appreciated to a young gun who will carry this knowledge and pass on the joy of tooling and boating.
     
  12. Capt Ram
    Joined: Jan 2011
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    Capt Ram Junior Member

    4 quarts in 3 hours says your lucky to go 1 mile-
     
  13. WickedGood

    WickedGood Guest

    I had that same Sraight Six in a 71 Chevy pickup truck.

    Ran it over 500,000 miles.

    I would say that the engine has given more than its lifespan and you can go pick up a Chevy 350 at a junkyard for a couple hundred bucks and just swap out the engine if the boats in good condition.

    dont bother trying to get a chevy V6 as they were junk.


    a Jeep straight 6, 4.0 ltr would be perfect
     
  14. mark775

    mark775 Guest

    "The Joy of Tooling And Boating"

    - Chapter one
    "running an engine with these problems until their just ain't nothing left"
     

  15. 73tomsawyer
    Joined: Aug 2010
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    Location: Iowa

    73tomsawyer Junior Member

    Do I risk doing damage to the cylinder head? I have thought about a new block from a junkyard.A couple hundred dollars ain't bad. I would want it rebuilt if I wanted it to last for longer than just trying to sell the boat off. I guess that would cost me too. BTW how would you go about removing an engine block from a junkyard, just start wrenching and throwing **** in the truck bed? Then get a dolly or fork truck and lift it out?
     
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