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The thermostat housing was oozing a tiny amount coolant all around the perimeter of the housing which was unacceptable. I removed the housing and found a normal looking 195F termostatat that was sealed with a gasket which was in poor shape. Now this car has the original small block engine that the car came with but with an upgraded Edelbrock Performer intake manifold. Looking through various suppliers they list both o-ring and gasket sealing types for replacement thermostat housings and thermostats.... so you know the question now - do I use a gasket or an o-ring? Some pics for context and reference....
For this application, I use a paper gasket with a light coating of "Indian head" shellac, on both sides of gasket,,, has always worked well for me, , , i only use o-ring if their is a milled recess for it in eather the intake or houseing,,,
Whatever gasket used has to match the thermo housing. I always sand the housing on a flat surface on sandpaper till its even. Keep turning the part different directions, and upon install dont over tighten the bolts.
Also use a 180 thermo for best all around performance
I was under the assumption that if you were going to move, swivel or clock the housing to line up with the rad hose, then use an "O" ring. In your case, a non-moving housing, I would think a Felpro paper or Mr Gasket silicone is your best bet.
Permatex makes a sealer specifically for waterpump gaskets and waterneck gasket. Small silver tube, Autozone, not cheap but works well for glycol situations where other Permatex could be ruined by anti-freeze.
I stopped using paper gaskets in the 90's...I only use a rubberized gasket like A felpro PermaDryPlus.....2-3X thicker than paper gaskets, rubberized which will seal most imperfections easily, and a raised center O ring for double sealing.....
I stopped using paper gaskets in the 90's...I only use a rubberized gasket like A felpro PermaDryPlus.....2-3X thicker than paper gaskets, rubberized which will seal most imperfections easily, and a raised center O ring for double sealing.....
I agree. They ( rubber / silicone) are pricey, maybe $22 but well worth a leak free thermo housing. And I believe you can use it over & over if you had to.
I agree. They ( rubber / silicone) are pricey, maybe $22 but well worth a leak free thermo housing. And I believe you can use it over & over if you had to.
The problem with using gaskets is the soft aluminum ears of the thermostat housing get bent downward. I used my bench grinder to grind my housing flat again and have used only RTV ever since. Assemble it "wet" and it'll never leak because some of the RTV will squish out on the inside; preventing the coolant from ever leaking.
The problem with using gaskets is the soft aluminum ears of the thermostat housing get bent downward. I used my bench grinder to grind my housing flat again and have used only RTV ever since. Assemble it "wet" and it'll never leak because some of the RTV will squish out on the inside; preventing the coolant from ever leaking.
Where do you come up with this stuff? If any part of that housing is bending, you need to upgrade to a quality unit.
Use a GM gasket with the soft center ring in the gasket, crappy gaskets will leak.
I have replaced many friends gaskets when they could not stop the drips...
1000%
I keep them on the shelf and are the only type I use now.
I do not use the Indian Shellac....I use a very thin layer of the the GREAT STUFF RTV...where it is thick bodied and not a really creamy type of RTV.
I actually take the thermostat housing over to the deck of my large drill press and place a piece of 180 grit sandpaper on it and slowing hone the surface flat IF I see after few swipes over the sandpaper that I can see that the surface is all warped. I know I would never take it to a bench grinder. I am just not that good.
Originally Posted by jb78L-82
I stopped using paper gaskets in the 90's...I only use a rubberized gasket like A felpro PermaDryPlus.....2-3X thicker than paper gaskets, rubberized which will seal most imperfections easily, and a raised center O ring for double sealing.....
INTERESTING...I looked at it and it basically looks like the GM ones but it is blue. The GM ones do have a double o-ring sealing area on each side and they are also thick. I am sure it has that plastic film coating like many Fel-Pro gaskets have on them. On some of the Corvettes I work on ...seeing any blue is not something that I can let go out the door.. But I still will look at one.
Something we discovered here on the forum at least a decade ago was often the T-stat housing bolts are just a tiny bit too long. Not sure the reason whether stock bolts are a tiny bit shorter than hardware bolts the same thread. Or replacement T-stat housings just aren't tall enough or even the intake manifolds aren't thick enough there. Well whichever but you should check and ensure the T-stat bolts aren't bottoming out and may need to remove some length.
I never used to like O-ring T-stat housings before and thought they inherently leaked. Thats all I use now as the swivel housings work great with aftermarket manifolds.
12-23-2017, 02:26 PM
79 - thermostat housing gasket or o-ring?
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