Hot Rods Thermostat housing leaking???

Question on thermostat housing gasket. (pictures)

Should I use the rubber O-Ring only (with or without gasket sealer?)
I have never used an O-Ring before.
Use the Fel-Pro gasket only?
Should gasket sealer be used?

Any input would be welcome.
jeff

 

I have offen wondered the same thing

 

I put good stuff if I have it. But the orange one works too. Always use sealer.
Check if your housing is flat once cleaned

 

The gasket with the O ring will keep the O ring from compressing. So no gasket with the O ring.

 

Have to have good clean mating surfaces for oring . Dry no sealer . I have seen where is no mating surface on the intake to mate to oring

 

If it came with an o ring, it’s designed to seal with an o ring. Use that, not the gasket.

 

I've never used anything but a gasket and Permatex II. Never had one leak.

 

Use some Oring grease, if you're really conscientious...

 

get rid of that housing, get one that's like the original, one piece of cast iron or aluminum, designed to use only a gasket.

 

Yep, you will never distort one of these GM cast iron thermostat housings.

 

You mean I've gotta take off the Oring type that's been on & off many times for manifold changes , etc & has never leaked a drop in 25 years , that seems silly . How about don't buy junk & learn to install things properly . Too bad some have had problems .

 

yours isn't leaking, why would you change it?

 

I always use an original iron one, and get it chrome plated.

 

...Not only do they warp when tightened, but the chroming process itself tends to warp them. Ditch the chrome one. I try to keep a few GM ones around in different configurations.

 

If you need a straight up type housing a Mopar one will work.

 

2/16/25 If your thermostat is warping, your probably over tightening it. You might want to try installing it using both the O-ring and paper gasket together along with some non-hardening Permatex Gasket Sealer.

 

Or you can whittle one up!

 

or get one for a van?

 

It is easy to say to use an "original" when the "original" will point it the correct direction. That is not always the case and I don't have the equipment nor expertise to fabricate one from scratch. I don't like the O ring style and always fight them to not leak but in my case that is the only way to get the coolant to the radiator. I use "just a dab" of silicone gasket to the o ring after running a flat file on the mating surface.

 

I have had nothing but bad luck over time with the o-ring style. Even if they seal when new, I have had the chrome corrode bad enough that they start leaking. I run original thermostat housings anymore as has been mentioned. I’m sure there are decent ones. But, cast iron ones always work great with a gasket and some sealant.

 

Just to add to the confusion:

Great for low mounted radiators

 

Maybe the gasket is there to keep from overtightening it and warping it when the o-ring is in place..........

Since you already have it, try it out and see how much gap there is when you just set it in place with only an O-ring.
If its very much, try it with both the o-ring and gasket or just the gasket. If it doesn't work and does leak, its not that hard to replace it..............

 

If the new one is all you have at the moment, use it with your choice of O-ring or gasket. Don't be skeered. If it doesn't leak, you're done. If it leaks, it's right there in your face. Take it off and do something else. Don't overthink it.
It shouldn't warp from bolting it down. If it does warp or leak, you've done something weird.

 

According to the x-spurts here. They're all junk , I wouldn't want junk on my car , right?

 

you can run that junk on your car if you want. That's your problem.

 

If you use it, take any chrome off the mating surface and be sure it's flat.

 

It's your advice column ....

 

My self I over years have used OEM ,
& all the other mentioned above & more, Some leak , trued up with file ,
Intake & housing .
Unless cracked ,some can weld , some not.
Something I just experienced in the last two weeks, My cars are garage kept,

In one of my Blown engine I run water with weepier, Its been under 30 degs @ night here , when I wanted to test , So I did not want to take a chance of freezing up radiator while driving / testing @ night , temp was staying @ 160-170 engine block with a 195 thermostat, shocking but So ,
I have 3 temp gauges One on each side of heads , & One near thermostat.
So I drained all water & even @ bottom of block both sides , 3 plugs .
Filled up with 50/50 , after change I did not get to test Rain & snow ,
Car setting in shop , afew days later
Coolant puddles under car , started looking around to see where leaking,
Then see leaks from several places ,
From pipe threads , I run lines from back of intake to front to a thermostat box I modify and made before thermostat, & hose clamps ,
Shocked / puzzled . No leaks with Water , but with 50/50 leaks .
So thinking Antifreeze thinner & oily.

 

I'd have to say from what I have seen personally the number of people who have trouble with those particular thermostat housings may be larger than the number who have never had a problem with them. I have never had one but know several guys who have had them and gave up on them because o leaks.
I'd say the key to success is having a perfectly smooth flat mating surface on the manifold, having a thermostat that the shell isn't too thick on and sticks up above that surface on the manifold and the housing is in perfect shape and not one you got at a swap meet for three dollars that had already been on someone else's engine. Plus the correct O ring and not just an out of the O ring selection box one.