Thermostat & gasket

  • Filter
  • Time
  • Show
Clear All
new posts
  • Aaz
    • May 2023
    • 4

    Thermostat & gasket

    What is the right place for gasket? Should it be between thermostat and housing?

    When I opened outlet the housing it looked like the old gasket was placed between head and thermostat. There were no leak. So I cleaned, tested and put the thermostat back in the same order head - gasket -thermostat - housing. There is no leak. Is this the correct order?

    Also, I had to replace the nut. Can I use the Home Depot's ones?
  • Dave Neptune
    Afourian MVP, Professor Emeritus
    • Jan 2007
    • 5063

    Yer becoming a mechanic already. Yes the nut should be fine. It is a good idea when replacing nuts, bolts or studs to get Grade 8 when you can. They are stronger heat treated steel and rust far slower than softer ones. Stainless is not a bad idea either in some cases.

    In "ANY" T'stat installation first determine whether the "recess" for the flange of the T'stat is in the block or the housing, that is where the T'stat should be first and the gasket between the housing and the block.

    When the T'stat is in the housing you can use a bit of Permatex to hold it in place so it does not fall when inverted in hard to reach installations. It is also a good idea to goop both sides with a film of Permatex for best sealing. The silicone style sealants work well on new and pristine parts however the Permatex will not allow moisture in as the oil saturated in cast iron will not allow the silicone to bond to the metal. Silicone works well on aluminum though and Permatex will stick to both. Permatex #2 or "aviation" grade are well proven.

    Dave Neptune


    • ndutton
      Afourian MVP
      • May 2009
      • 9777

      The recess groove is in the housing as Dave said so the gasket goes directly on the head. I just did this last Monday exactly as Dave described including using Permatex #2. Upon start-up there were zero leaks.
      1977 Catalina 30
      San Pedro, California
      prior boats 1987 Westsail 32, 1970 Catalina 22
      Had my hands in a few others