Technical Sealing a thermostat housing.... opinions?

@Al T I have the chrome die cast garbage water neck on the Ole Hotrod didn't use gasket maker ( wish I did) and the gasket actually seemed to act like a sponge and it does leak not enough to be concerned right now...but I had a friend give me a bead blasted original and upon close inspection it had stress cracks where the tab meets the radius on both sides...he bead blasted another and I thought it was okay and low and behold it has hairline cracks as well. One was hollowed on mating face like yours the other was solid...so long winded but closely inspect the areas for Hairline cracking and heavy deep pitting inside water flow areas.​

 

If you lap it flat, then use Permatex 22071 with NO gasket, then let it set up for 24 hours, it won't leak. Gaskets don't work well because almost everyone overtorques the bolts and bend the ears. If you lap it flat, it will mate up with the flat surface on the intake and a small bead of the sealant will seal the inside mating surface. That's all that is needed. I gave up on gaskets for these.

https://www.permatex.com/products/g...ex-water-pump-thermostat-rtv-silicone-gasket/

 

Log onto Rockauto and order up a nice cast iron housing, verify it’s flat, paint it the color of your choice and put it together with a little Indian Head on the housing to hold the gasket and dry on the intake. Assemble, fill, and cruise!


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The gasket is made with a crush factor in it, if it needs any other sealant the manufacturer of the gasket would have called for it. Clean both the intake and thermostat housing and torque the bolts and it should be good. If it leaks some thing it not level then repair that and save your self the head ache. Gasket maker and permatex have a use but not needed on every thing. just my through on it.

 

I don't use the chrome ones, I used the gm aluminum ones. Glass bead it, sand and polish to desired luster, take a 6" adhesive DA 180 grit pad and stick it on your work bench and sand the mounting surface perfectly flat. Then a little RTV and gasket. Never leaks.

 

I have found that the only way I can tighten the housing down good enough is if I use studs in the manifold, not bolts. Bolts tend to loosen with expansion/contraction. I also use nyloc nuts on the studs. No leaks, ever.

 

How many of these have I installed in the last 45 years? The Aviation stuff in the tube always works, so does that Indian Head shellac... messy as hell. I would consider The Right Stuff sparingly with no gasket. The water neck on my car is the o-ring type, I used nothing on that.

 

Heck, usually put thermostat housings and water pump gaskets on with nothing but a light coat of grease- holds the gasket lined up and you don't destroy it if you have to remove the thermostat on the road in the middle of the night.

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Like Billy said, but he should have unlined “ little”! I hear talk and see evidence all the time of RTV squeezed out around gaskets. You don’t need that much. If any ,save a tiny bead, squeezes out you used too much.
And... I put the parts together as quickly as possible so that the RTV is still wet,so that it adheres to the mating part that is clean enough to eat off of.
I used that method to do the top end on a 1979 Shovelhead in 1983.Today that engine still gets dusty. If it works in that app, it will work anywhere.

Bones