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Technical Thermostat sealant of choice

Discussion in 'The Hokey Ass Message Board' started by NAES, Jun 6, 2019.

  1. NAES
    Joined: Dec 24, 2008
    Posts: 434

    NAES
    Member

    I know this topic has been beaten to death on just about every car forum out there but for the life of me I cannot get my thermostat to not leak.

    I have an aluminum Edelbrock intake which I have filed flat and there's no pits, etc. I just put a new AC Delco tstat housing on, used the supplied gasket and sealed both faces of the gasket as well as both metal mating surfaces and the bolt threads (after chasing with a tap) with Indian Head shellac. I've used Permatex blue and gray as well as Toyota FIPG with no luck. I let the shllac dry overnight and as the engine sits here and runs its blowing boggery bubbles in spite of retorquing.

    Any ideas?

    Sent from my SM-N910V using The H.A.M.B. mobile app
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 43,180

    squirrel
    Member

    is it a chrome housing? or what? The brand name doesn't tell us much, unfortunately.

    Can you see where it's leaking?
     
    Nailhead Jason likes this.
  3. 19Fordy
    Joined: May 17, 2003
    Posts: 6,385

    19Fordy
    Member

  4. KJSR
    Joined: Mar 7, 2008
    Posts: 2,130

    KJSR
    Member
    from Utah
    1. Utah HAMBers

    Take a video and post it........
     
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  5. dirrty
    Joined: Dec 10, 2011
    Posts: 16

    dirrty
    Member

    Use a housing with an "O" ring, gaskets are not very forgiving.
     
  6. use a good quality gasket. the ones in the T-Stat boxes are typically crap. Use a good thick Fel-Pro gasket. when you put the T-Sat in the intake manifold put a thin amount of Grey Permatex around the edge of the thermostat and put it in the in manifold. then put a small bead around the opening in the thermostat housing and the bolt holes. if you can use an original thermostat housing, Most all of the aftermarket ones are piles of shit.
     
    lothiandon1940 likes this.
  7. brigrat
    Joined: Nov 9, 2007
    Posts: 4,781

    brigrat
    ALLIANCE MEMBER
    from Wa.St.

    You said that you flattened the Aluminum manifold but most thermo housings are also "bowed". You can true up the housing but I find that torqueing the 2 bolts will bow it again, just a cheap bad design. O ring is best, if using gasket I use Ultra Grey..................................
     
  8. Terrible80
    Joined: Oct 1, 2010
    Posts: 700

    Terrible80
    ALLIANCE MEMBER

    Do the mating surfaces match? I had a Mopar housing that had to be perfectly centered to not leak. Pos, but working for now.

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  9. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 5,350

    Bandit Billy
    ALLIANCE MEMBER

    I always plane the t-stat housing, new or used. Start with a flat file across the entire mounting area then I like to stick a 180 grit DA paper to the work bench where it is nice and flat, place the housing on it, apply pressure and sand the shit out of it. Then permatex silicone, paper gasket, more silicone and twist it down. Let it dry before adding water. Never had one leak. Polished aluminum is ok, chrome is crap.
     
  10. Chappy444
    Joined: Jan 27, 2012
    Posts: 808

    Chappy444
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    1. Maryland HAMBers

  11. Oldioron
    Joined: Dec 12, 2018
    Posts: 844

    Oldioron
    Member

    At one time I would make sure everything was flat and put 3M black weather strip adhesive on the gasket and the metal parts let it all set up and set it together. Most of the time it would work on my mopars and that's saying something.
    Not sure what but something. :)
     
  12. TimCT
    Joined: Jun 6, 2017
    Posts: 100

    TimCT
    ALLIANCE MEMBER

    Echoing what others have said - check the housing to make sure its as flat as the intake. I've always used Permatex #2 non-hardening on water pump and thermostat housing gaskets - both sides. The only thermostat housing that ever leaked on me was one of the charming cheapie chrome swivel housings with an O ring. Swapped that out for a Billet Specialties piece (sorry for the B word) and that one sealed fine.
     
  13. NAES
    Joined: Dec 24, 2008
    Posts: 434

    NAES
    Member

    Ok thanks everyone for the help. I guess I didn't mention it but I also filed the Tstat housing flat as well. It is an aluminum AC Delco with a raw finish.

    The only other thing I can try is a thicker gasket and one of the above mentioned sealants.

    Thanks again everyone. NAES

    Sent from my SM-N910V using The H.A.M.B. mobile app
     
  14. NAES
    Joined: Dec 24, 2008
    Posts: 434

    NAES
    Member

  15. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 1,641

    2OLD2FAST
    Member
    from illinois

    You won't warp the housing if you don't over- tighten the bolts ....
     
  16. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 1,641

    2OLD2FAST
    Member
    from illinois

    You say you filed the manifold , if you took off too much material , the stat flange may not be seating and won't allow the housing to pull down completely.....
     
  17. jimmy six
    Joined: Mar 21, 2006
    Posts: 4,551

    jimmy six
    ALLIANCE MEMBER

    I'm a Permatex #2 guy on all water joints. Use vinyl gloves as that black shit will get everywhere you don't want it. I put it on both side on the gasket and nothing else. They never leak for me.
    Make sure the recess for the thermostat has enough meat to place it correctly. If there was one on the manifold and you filed if off, now the housing will need to have one.
     
  18. BigChief
    Joined: Jan 14, 2003
    Posts: 2,042

    BigChief
    Member

    I'm a Hylomar man myself. Make sure everything is really flat...relative...relative to each other....assemble without gaskets or Tstat ...finger snug the bolts and used the a bendalite around the inside with the shop lights off looking for any air gaps.

    Sent from my SM-G950U using The H.A.M.B. mobile app
     
  19. I had the same problem, and after several tries with new gaskets, goo, etc, I ended up putting the housing in the mill and skimming it until flat. Installed and problem gone.
     
  20. 26hotrod
    Joined: Nov 28, 2009
    Posts: 809

    26hotrod
    Member
    from landis n c

    I use Permatex clear rtv sealant on the "O" ring on a Billete Specialties aluminum housing. I smear the Permatex all over the "O" ring on both sides and bolt it down as usual. Let it set over nite and so far no problems. This is on an aluminum manifold. I'm sorry I also used the "B" word and I will try to do better...………….
     
  21. OLDSMAN
    Joined: Jul 20, 2006
    Posts: 1,816

    OLDSMAN
    Member

    I have never used any kind of a sealer on thermostat housing gaskets. Just put them on dry, and I have never had any leaks.
     
    clem likes this.
  22. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 1,641

    2OLD2FAST
    Member
    from illinois

    You're either haven't done very many or you're extremely fortunate ....
     
  23. I don't use nothing but the gasket, all that sealant is good for is make a mess . A new gasket has a crush factor in it. If it leaks some thing is not flat, Good luck.
     
  24. chevyfordman
    Joined: Oct 4, 2008
    Posts: 770

    chevyfordman
    Member

    Blue Monster has worked for me.
     
  25. OLDSMAN
    Joined: Jul 20, 2006
    Posts: 1,816

    OLDSMAN
    Member

    I was a professional mechanic for 40 years so yes I have changed just a few thermostats in my life. My convertible doesn’t leak a drop of coolant, and the gasket was out on dry
     
    clem likes this.
  26. BamaMav
    Joined: Jun 19, 2011
    Posts: 3,236

    BamaMav
    Member
    from Berry, AL

    I’ve did them both ways, dry with a good thick gasket, or wet coated with Permatex Ultra Copper or Ultra Black. Seldom had one leak, not even the chrome ones.
     
  27. bigdog
    Joined: Oct 30, 2002
    Posts: 475

    bigdog
    Member

    Way back in 1974 when I was in auto mechanics class the grumpy old instructor said something like,"If you put it together right you don't need that shit." I've figured out he's right. If it leaks somethings probably not flat.
     
  28. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 1,641

    2OLD2FAST
    Member
    from illinois

    Extremely fortunate....
     
  29. I've used Gasgacinch for about 40 years, I find it works well.
     
  30. WB69
    Joined: Dec 7, 2008
    Posts: 782

    WB69
    Member

    Have seen that before. Not as uncommon as one would think actually.
     

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