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Easiest and surest way of testing for blown head gasket?

Discussion in '1982-Present GM Diesel' started by FWP, Jul 29, 2004.

  1. FWP

    FWP CRS

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    I'm thinking radiator test cap. Down and dirty, easy to do. I'm seeing some small bubbles with the cap off, but I just re installed the radiator (Got a few minor leaks fixed on it), so it may be air still in the system. I just want to eliminate the head gaskets, and get some piece of mind on that.

    Any other thoughts for an easy way to check for a blown head gasket??
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Leak down test is the best way I have heard of.

    Rene
     
  3. FWP

    FWP CRS

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    I'm not following ya Rene, explain it to a dummy /forums/images/graemlins/ears.gif.

    BTW, I just finished testing the cooling system with my homemade pressure gage, didn't get over 1 psi, system hot, t-stat open, idle.
     
  4. BlueBlazer

    BlueBlazer 1/2 ton status

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    You test the cooling system with the engine off.

    Leakdown test involves applying air pressure to each cylinder and seeing if it holds the pressure or leaks it. If it leaks, you can find out if its leaking past rings, valves, or head gasket. If its a gasket, then when you apply air to the cylinder that has the leak, bubbles will form in the coolant and you will usually hear it too.
     
  5. FWP

    FWP CRS

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    Ah, gotcha, makes sense. Like I said, I ain't none too bright /forums/images/graemlins/rotfl.gif
     
  6. FWP

    FWP CRS

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    OK, got 10 psi in the cooling system, waiting for leakdown. How long shoud I wait? How fast would the pressure drop if there was a problem in the head gasket???
     
  7. BlueBlazer

    BlueBlazer 1/2 ton status

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    Leakdown and cooling system pressure check are two totally different animals. You will need to get a fitting that will fit the glowplug hole on one side and an quick disconnect for air on the other, then apply regulated air to it, see how fast it drops if at all, if it does leak, see where is leaks from.
     
  8. FWP

    FWP CRS

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    I understand, thank you.

    Question... If the head gasket is leaking at one of the coolant ports into a cylinder, wouldn't I see it in a pressure check of the cooling system? I guess that's what I was asking in my previous post, maybe I wasn't clear, sorry bout that.
     
  9. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Yes, if the gasket is badnear a coolant passage. However a head gasket could still be bad and not blow bubbles into the coolant. It could bleed compression into the next cylinder or almost anywhere. The leak down test is cool in that it will find a problem if there is one...and...tell you exactly where the problem is down to the cylinder and how the gasket is leaking. It'll also find burnt valves, bad rings etc etc.

    Like Tyler said you need a fitting that will thread into a GP hole, compressed air, a shut off valve of some sort and decent hearing.

    Rene
     
  10. FWP

    FWP CRS

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    Cool, got it. /forums/images/graemlins/thumb.gif
     

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