Ok, I was banging my head last with what seemed to be a simple process.

I flushed out the coolant and put on a new thermostat the other day. All went well but I noticed a hairline crack in the thermostat housing that would not leak completely, but would let out just a drop of coolant when I burped the upper radiator hose. No big deal, I thought, just change the thermostat housing. So I got a new one at Napa yesterday, and proceed to install.

Long story short, I went through 2 gaskets because every time I refilled with coolant, a leak would spring from the bottom right side of the housing. I used silicone RTV on the gasket on the first attempt, on the second, I used the red RTV gasket maker and got the same results. I did let the sealant "cure" for about an hour after each application. Clueless as to whats going on. Questions/caveats:

1. Coolant was not completely drained from the block, so would having coolant in close proximity (perhaps dampening the contact surface) have an effect on the seal?
2. Outside air temp was close to freezing last night while I was working on this, does that have an effect on the amount of time it takes for RTV to cure?
3. Thinking about trying the permatex right stuff on the gasket. Yay or Nay?

 

 

the 'RIGHT STUFF " will work but I have hated myself when I had to take it back apart lol that stuff sticks too good !

 

Thats what I've been reading. So how do you go about taking it apart without prying and damaging the aluminum or cast components?

 

Use a soft (softer than aluminum) prying tool— e.g. a nylon trim pry tool, and GO EASY. Another option, and your mileage may vary, is to pry it with the larger inlet/outlet section on the housing, but this could damage your thermostat— Since I was replacing mine anyway most recently, it didn't bother me.

My reliable go-to for thermostat gaskets has been cereal box cardboard—no, really. Recently I've found foam-like crap gaskets that come with the water pumps, but cereal box cardboard is what I use.

And I apply a LIGHT coat on both sides with Permatex high tack spray-a-gasket sealant (the red stuff, NOT COPPER). Let it set a few minutes before you put it down on the metal, too. You don't want too much, but you want enough to tack the gasket to the housing.

 

Sealant on bolts! There is 1 or 2 that goes into the water jacket too.

 

I'd also make sure the thermostat is seated correctly before bolting it all back up.

I believe the thermostat can fall down out of its groove and prevent the housing from sealing properly.

 

Cracked cylinder head.