Engine - thermostat housing keeps leaking | Ford Escort Owners Association (FEOA)
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Engine thermostat housing keeps leaking

Discussion in '2nd Gen 1991-1996 1.9L SOHC' started by axa, Sep 20, 2020.

  1. axa

    axa FEOA Member

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    so after 24 years i decided to do a full coolant flush, long overdue... so there was no way of getting it clean without removing the thermostat and stick a hose in the block.... the worst brown crap you'll ever see...
    changed the thermostat, put it all back together.

    it leaked, somewhere on the bottom of the housing near where the heater return hose. replaced the 5" return hose, got a new gasket, applied the silicone even more carefully, finger tightened, let it sit several minutes, then torqued to spec. and soon after, it's leaking again from what appears the same spot.

    ive done this job before without
    trouble, didn't notice cracks anywhere, anyone got any tips?
  2. zzyzzx

    zzyzzx FEOA Member

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    How long did you wait for the sealant to cure?
    How pitted was the housing?
  3. denisond3

    denisond3 Moderator Staff Member

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    Glad to hear of your maintenance action. It can be difficult to tell where a leak is, since its going to get the bottom of things wet even if the leak is higher up.
    Is it possible the leakage is between the head and the thermostat housing? Those surfaces can be corroded enough to require heavy sanding to flatten them. I use a thread tap to clean out the threaded holes going into the block. I think it is a 6mm-1.25 tape. And before I run the little bolts back in, I wipe some antiseize onto their threads. I never put a steel bolt into an aluminum threaded hole without a little antiseize on the threads.
    I put sealant on both sides of the paper gasket and use a small torque wrench to get the three bolt tightened down; and Im careful putting sealant around the narrow area where the small hole into the thermostat housing is.

    I usually find it necessary to sand down the two outlets (to radiator and to heater inlet hose) to remove crud and corrosion. I may use permatex RTV sealant - my favorite being their "ultra black" product. I then let any sealant cure overnight. When using the original spring clamps I install them and havent had leaks. With screw clamps I tighten them down snug, but comeback a couple of days after using the car, and retighten the screw, then do that re-tightening a couple of weeks later. The rubber of the hose will 'give' enough to need another turn or two of the screw clamp.
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  4. zzyzzx

    zzyzzx FEOA Member

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    I think it's a M6-1.0

    The OP should see if they have a coolant system pressure tester as a free loaner tool at a local auto parts store. In Anne Arundel County MD, that would be an Advance Auto.
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  5. marclar

    marclar Administrator Staff Member

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    can you get an inspection mirror under the housing? it is possible the housing is pitted, OR one of the small bolts could be partially stripped out not allowing it to clamp as designed. the housings are super cheap, may be in interest to replace it.
  6. axa

    axa FEOA Member

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    would you elaborate on "super cheap" best i could find is about 35$ plus shipping.
  7. marclar

    marclar Administrator Staff Member

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  8. axa

    axa FEOA Member

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    good info here...
    i would say i was doing most of what was suggested... anti seize, cleaned the mating surfaces, applied rtv to both sides of gasket, pretty carefully... cleaned the hose barbs

    i didn't check carefully enough for cracks i guess as i didn't consider it... didn't retap the holes as i didn't think it an issue, but I'm going to look more closely for all this next time...

    i hate the fact that there is often an unnecessary next time...
    Last edited: Sep 21, 2020
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  9. axa

    axa FEOA Member

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    not pitted at all from what i recall.

    i don't recall exactly how long i let the sealant cure but i did take heed of the suggestion in the manual.... i have to be more careful about everything next time
  10. marclar

    marclar Administrator Staff Member

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    could be chunk of something in the lower bolt hole (s) that is preventing the screw from going in all the way.. this also can happen if excessive silicon gets into the threads prior to installing. effectively creates a hydrolock situation inside the thread bore.
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  11. henryinSATX

    henryinSATX FEOA Member

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    Assuming that you've gone as far as you can trying to seal it, you could try running the coolant system w/o pressurization. Just remove the rubber seal that contacts the inside lip of the radiator spout. this prevents any seal and buildup of pressure. leave the other one in the cap, that's a vacuum seal, so it sucks coolant back into the radiator on cooldown. I run mine like this, with a 180 degree stat and straight antifreeze, no dilution. This may cure the leak.
  12. axa

    axa FEOA Member

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    radiator spout?
  13. denisond3

    denisond3 Moderator Staff Member

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    That lip contacts the smaller 'lid' on the radiator cap.
  14. zzyzzx

    zzyzzx FEOA Member

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    There is a 5PSI cap that fits this radiator perfectly.
  15. henryinSATX

    henryinSATX FEOA Member

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    ya know, that NEVER occurred to me, I thought they were all around the same pressure.

    from something post-war hopefully

    ..."Jeremy, when I was your age, we had a '48 Kaiser Manhattan,and dad made us kids go crank the pump to pressure up the cooling systen before we could start it!

    and we LOVED it...you spoiled kids nowadays"

    so, which car's it on?
  16. zzyzzx

    zzyzzx FEOA Member

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    Stant 10268 will work on this car and is 5PSI.
  17. henryinSATX

    henryinSATX FEOA Member

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    "]Stant 10268 will work on this car and is 5PSI.

    Thanks, that'll be handy when I fix the AC

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