Thermostat gasket leaking AGAIN!!!!

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J

jfive

Well-Known Member
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Nov 17, 2023
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Location
Elkmont, AL
1970 Swinger 318

ok so in the process removing and installing the engine i replaced the thermostat and gasket. after getting fluids in i noticed it was leaking, must have dine something wrong.....
so i went and got another gasket pulled it resealed it, re-torqued it, added fluid, now leaking again. I don't even have engine running yet and water/coolant has pooled up on the water pump top, running off intake and a little on the intake. I went with a Felpro both times, not sure of part number off hand, and it had a paper on one side that you peel off and has sticky material on it. the first time i used Permatex on both sides, it leaked so i thought maybe not on the sticky side since it is already something there? when removing it i noticed that the film that was no longer part if the gasket, it appears that the sticker part of the gasket was no longer stuck to the gasket after the water/coolant mix touched it, that's where the leak came from. so i only used Permatex on the one side the second time around, and i am still leaking. with all that being said, what did i do wrong? or was it just a janky gasket both times? any recommended gaskets?

thanks in advance everyone.
 
Is it one of those chrome thermostat housings?

Years ago I tried a bunch of different gaskets and tried sanding both the surface of the intake and the thermostat housing cover and it would always leak. I then bought a Billit housing with the o-ring gasket and it’s not leaked since.
 
Get a Flashpower #181491-200. O-ringed housing. This is for the large thermostat. When torquing, we are talking inch lbs, not Foot lbs, 15- 25. Had your same problem, not a anymore.

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@ H22A4 - I have scraped, with a plastic razor, and then used 600 grit paper on it both times, was nice and shiny, dry surface

@Dartsun - yes stock housing

i will look into another housing, but this one didn't seem to be leaking before i removed it, but i only had the car running for a few minutes a few times. so i am not sure what I did wrong, or it is just that temperamental about sealing up? i have changed a thermostat before, not this car but another 318 '70, although it was some years ago.... and do not recall the gasket having a sticky side so i was thinking maybe the gasket just sucked, lol
 
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Both sides of the gasket..... I use this **** on anything that can leak pretty much and never have an issue
 
jfive said:
i used Permatex, just not that specific one i don't think. mine was a tube. it was Black and very thick.


so if i get the O-ring style do i still need this?
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probably not.. but if you use that you won't need the o-ring style... the aviation sealer is more a shelac that brushes on, a very thin layer and it 100% will not leak..
 
No sealer on the o-ringed housing. You may want to run a file or sanding block over thermostat base on the intake, just to be sure that it is flat.
 
BTW, your current housing, check it for flatness, people overtighten them and can bend them a bit.. not common but worth checking.. and i use aviation on timing cover/water pump/thermostat, rtv on oilpan/china walls and such..
 
i guess i am still puzzled as to why it is leaking. it seems to be the gasket coming apart at the factory sticky surface, are all gaskets that was now?

if i used that Permatex that @Icetech says will i still need a gasket? i assume yes, so if i get the same type of gasket then how does that solve that issue of the gasket failure? i believe this to be the failure point as the first time i remove the housing the Permatex i used was very well stuck to all parts of the housing and the intake. the clear film, that used to be sticky was on one side and gasket was on other. i have not remove this time to see where the failure is. got frustrated as i was working on a fueling issue and seen this leak AGAIN!!!
 
I'm sure the billet housings are awesome, but the Permatex Form-A-Gasket is great stuff. Cheaper and worth a shot.
 
CRUZE 418 said:
No sealer on the o-ringed housing. You may want to run a file or sanding block over thermostat base on the intake, just to be sure that it is flat.
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yes have a flat surface that i stick sandpaper on then can sand flat, came out shiny with 600 grit, intake seems to be flat, i used a flat block i have for it, all looked smooth, clean and straight
 
jfive said:
i guess i am still puzzled as to why it is leaking. it seems to be the gasket coming apart at the factory sticky surface, are all gaskets that was now?

if i used that Permatex that @Icetech says will i still need a gasket? i assume yes, so if i get the same type of gasket then how does that solve that issue of the gasket failure? i believe this to be the failure point as the first time i remove the housing the Permatex i used was very well stuck to all parts of the housing and the intake. the clear film, that used to be sticky was on one side and gasket was on other. i have not remove this time to see where the failure is. got frustrated as i was working on a fueling issue and seen this leak AGAIN!!!
Click to expand...
You keep saying permatex but i think you mean RTV you used? (silicone) it sucks for water parts.. the aviation dries hard and will basically glue the gasket in place (get a new gasket) the RTV stays soft-ish and can let the gasket move/expand a tiny bit.. i know it sounds odd.. but...
 
thermostat leaks are par for the course honestly.... once you go with the aviation you will never have issues again. You can get it at any local auto parts and prolly even walmart
 
BTW, you aren't using a chrome thermostat housing are you? cause they should just be called "Always leak housing! now in chrome!"
 
One last thing.. if any squishes out when you tighten it down... DO NOT attempt to clean it up while wet.. it will smear and you will 100% have a brown shitstain forever where it smeared :)
 
Icetech said:
You keep saying permatex but i think you mean RTV you used? (silicone) it sucks for water parts.. the aviation dries hard and will basically glue the gasket in place (get a new gasket) the RTV stays soft-ish and can let the gasket move/expand a tiny bit.. i know it sounds odd.. but...
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yea, maybe it is RTV, i will stop by the O' and get some of this Aviation Permatex, and another damn gasket, lol.

ill let you guys know how it goes, probly good since i got the advice on here. :thumbsup:
 
jfive said:
yea, maybe it is RTV, i will stop by the O' and get some of this Aviation Permatex, and another damn gasket, lol.

ill let you guys know how it goes, probly good since i got the advice on here. :thumbsup:
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you will be happy.. and one thing of that sealer will literally last you 25 years.. the **** goes a LONG way
 
well i just searched all my local resources and noone has this stuff in stock, go figure. ill get some ordered only a day to store shipping. but this is just my luck, :BangHead:
 
jfive said:
well i just searched all my local resources and noone has this stuff in stock, go figure. ill get some ordered only a day to store shipping. but this is just my luck, :BangHead:
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there isn't a auto parts store near you? like every store will have it... that's really weird..
 
No biggy.. one day won't matter.. looked at the advanced auto near you and i am really surprised they don't have it
 
oh yea there's plenty. in the town i work in there is an O'Reilly, 2 Autozone and 1 Advanced, oh and a NAPA, then by the house i have 1 of each as well. noone has this stuff, it is either supper popular and they cant keep it or noone around here has every heard of it. yea been this long waiting to run whats another day.... or week really, lol
 
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