Thermostat housing leaks after a simple replacement job...

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Mr.cant-find-his-10.5-mm

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So I just replace the thermostat in my 95 Chevy 1500 with the 5.7 today. It was a very simple job, took around half hour to complete. I put in an ACDelco thermostat with a fleepro rubber gasket. Everything sits in there nicely. Torqued the two bolts to 20 ft-lb and call it a day. After refilling the coolant I notice a small leak coming from the thermostat housing. I'm really frustrating now as I cannot figure out what I did wrong.

Any help would be greatly appreciated, thanks.
 
This happened to me with my Ford. I could not for the life of me get the thermostat housing to seal. I finally took it to a shop. They used "the right stuff " and apparently that stuff works. No leaks since.
 
Originally Posted by Chris142
Is the housing flat?

double post - sorry. FWIW, I've had good luck with "paper" gaskets and some Permatex Grey.
 
Last edited:
Originally Posted by Chris142
Is the housing flat?


Yep it's flat. Never had a leak before.


Originally Posted by ag_ghost
Originally Posted by Chris142
Is the housing flat?

double post - sorry. FWIW, I've had good luck with "paper" gaskets and some Permatex Grey.




I know some GM trucks had a gasket between the housing and the intake manifold, but mine does not. It only had a o-ring on it.
 
Originally Posted by PotatoFarmer77w
Originally Posted by tig1
You may have cracked the housing. 20 ft lbs seems high to me. Is it cast aluminum?


That's what it says in Haynes manual.

I just checked another source on line and it showed 30 ft lbs.
 
I always run a file over the t-housing face and the intake. I have some broken files that fit in almost anything. The RIGHT STUFF is $$$$$$$$$ but it works.
 
As the aluminum housing corrodes and pits, the seal gets much harder to make.
A new AC Delco housing is $17 at RA.
That and some Hylomar sealant and you should be all set.
 
Originally Posted by P10crew
The gasket should be molded silicone/ aluminum.
Not rubber

That gasket is typically paper.

Both surfaces clean to bare metal, use a new paper gasket and Permatex Aviation Form a gasket and torque to spec. Never a leak.
 
Originally Posted by tahoe_hybrid
did you bother to replace the seal? you can always get one of those make your own seal deals if your that lazy

His is basically an oring with a groove that the thermostat sits in.
 
Make sure both sealing surfaces are spotless and use Permatex high tack or Hylomar on both sides of the O ring. On stuff like this I never bother with a torque wrench.
20 ft.lb is close to the bottom of the scale for many tools making them inaccurate just tighten in 2 steps to compensate for compression of the rubber is fine.
 
Originally Posted by edwardh1

what does Toyota do?


The same as this '95 Chevy when things are no longer perfect after 25 years!

Did you clean out the bolt holes real good with a 3/8-16 thread chaser along with taking the bolts to a wire wheel? Adequate clamping force cannot be achieved with dirty bolt holes & hardware!

The Intake manifold side also tends to pit.....Where High Tack or Hylomar works great as Trav pointed out, Permatex Aviation Form-a-Gasket also works well
 
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