Pressure Test

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  • ndutton
    Afourian MVP
    • May 2009
    • 9777

    Pressure Test

    Gauge and Schrader valve all in one. Just before posting I checked Home Depot's price, $10.
    Attached Files
    Neil
    1977 Catalina 30
    San Pedro, California
    prior boats 1987 Westsail 32, 1970 Catalina 22
    Had my hands in a few others
  • CalebD
    Afourian MVP
    • May 2007
    • 900

    #2
    This one?

    Wouldn't I need some kind of fitting to adapt to the spark plug holes as well ?

    Tartan 27 #328 owner born 1958
    A4 and boat are from 1967

    Comment

    • ndutton
      Afourian MVP
      • May 2009
      • 9777

      #3
      Yeah, that works. HD has this one too


      The test is of the water jacket, not the combustion chamber so the spark plug hole is not involved. Using the example gauge/valve assembly on the manifold, adapt the threads to fit a water inlet on either end on the top, plug the other one and pump up to [insert preferred pressure here] psi. 20 psi is frequently mentioned on this forum but I think that's excessive considering our cooling systems operate at much less (4 psi or so for FWC, 0 psi for RWC). I'd suggest 5~10 psi for a reasonable test.

      A manual air pump is all that's needed. If you're using compressed air, be careful. This is intended as a diagnostic test, not a destructive one.
      Neil
      1977 Catalina 30
      San Pedro, California
      prior boats 1987 Westsail 32, 1970 Catalina 22
      Had my hands in a few others

      Comment

      • Dave Neptune
        Afourian MVP, Professor Emeritus
        • Jan 2007
        • 5063

        #4
        Caleb,, the pressure test is for testing the integrity of a sealed system like the water jackets at LOW PRESSURE.

        Testing the cylinders is a different story as the rings are designed with a gap so they won't seal. If they do seal the top of the piston will be compromised or pulled in half. there is a test commonly called a "leak-down" test of the cylinders. This is done by injecting air into the cylinder and "listening" to the crankcase for air leakage and a guess as to the severity of the leak.

        Dave Neptune

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        • JOHN COOKSON
          Afourian MVP, Professor Emeritus
          • Nov 2008
          • 3501

          #5
          The Ultimate Leak Down Test

          Many years ago I have my car at the shop to have some work done on it.
          It was a one person shop. A couple of gents showed up with a VW engine wanting to know if they needed to tear the engine down further and replace the rings. The mechanic took the air hose to each cylinder and pressed the trigger. The verdict: The compression was fine. I assumed he could feel the resistance on his arm.
          Dave N. or anybody; ever hear of anything like this?

          TRUE GRIT

          Comment

          • ndutton
            Afourian MVP
            • May 2009
            • 9777

            #6
            Leak down test explained
            Neil
            1977 Catalina 30
            San Pedro, California
            prior boats 1987 Westsail 32, 1970 Catalina 22
            Had my hands in a few others

            Comment

            • CamaroMan
              • Oct 2017
              • 42

              #7
              Make sure the actual pump doesnt leak.. I made on similar to this for outdrive tests - its pointless if the pump leaks anywhere since a pump keeps the valve open when connected (of course you could pull it out quickly but that usually costs u a few psi - not good on lo pressure tests). I put my pump in a bucket of water pressurized and lo and behold - bubbles.

              I bought a one way pressure activated valve on amazon for 5 bucks that I plumbed in after the schraeder valve - it makes sure air can only go one way - works like a charm!



              Last edited by CamaroMan; 10-30-2017, 10:02 PM.

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