I have a problem that is driving me nuts, a leaking thermostat housing. I have tried everything I know to fix it. I had a chrome one which leaked so I went back to the stock one which also leaks, though not as bad. I also have tried different sealants, but nothing seems to work. I have replaced many thermostats in my life and never had a problem , so I am stumped Any suggestions would be appreciated. The engine is a 68 plymouth 318 with a edelbrock performer manifold THANKS

I had that same problem with the performer on my Chevy 350. I finally just used Permatex sealer on all surfaces, and haven't had any problems since...been about five years. I have the original style housing.
phil
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One man's treasure is another man's trash.

I use silicon or RTV or what ever you call it. I use it with a gasket but there are people that don't use one. The trick with RTV is to put it on and don't tighten it down for about 24 hours. Put the part on and make it just tight enough to form the surface and wait. This works on any gasket I have tried wether it is a oil pan or what ever......Ray
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Grump

I have the O ring type on my SBC performer & it leaked so I used the O ring, a stock gasket & RTV & it doesn't leak anymore.

Hi Stoke, Take your thermostat housing & a piece of 80 grit sand paper or a finner grit. Tape your paper to a flat smooth surface. (could use shop floor). Now rub your thermo housing gasket surface dowm on the sand paper in a circular motion. Look at it and repeat until its flat. Do the same on your intake using a sanding block. Try with your chrome one first, sometimes the chrome surface is to smooth to work as a gasket surface. Blue gasket sealer should work when surfaces are roughed up and flat. Let me know. Regards,HonestFrank
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"VEO DINDICE"

Hi, I find that some of those import chrome thermostat housings are just junk out of the box. a Quick cure that I use is my d.a. sander with 80 grit on the warped housing. A decent belt sander will do, but they are a little awkward to handle. A good gasket and a little "sillycone" and care not to over torque should do the trick.

I stay away from the chrome housings. Most are aluminum or pot metal and warp very easily. I usually buy a cast iron replacement part like Everco or Four Seasons. Paint it engine color and it lasts forever.

bjb
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There's a world of difference between "good" and "good enough".

I put one of those Chromed hood ornament-pot-metal-zinc housings on my truck years ago, the kind with the neat little O-ring that looks so fool proof.
Then about three months later I overheard someone talking about them being junk and corroding away from the inside.
I took mine off and found that in just the three months it had literally dossolved down to the point that there was just the chrome shell in spots.
I think the only reason it didn't blow is because at the time I was running a non-pressurized radiator.
You see, the zinc in those housings works like a zinc on a boat.
On a boat it's the zinc's job to dissolve through electrolisis so that other more important metal fittings don't.
I replaced it with a cast iron housing, painted to match the Krylon green waterpump and engine block....
And yes, the gasket leaked...
I did the sanding trick with the samdpaper taped to a piece of flat laminated glass and used the new black Form-a-Gasket sillycon, and did the only snug till it sets and then torque it the next day routine on the Form-a-Gasket.
That worked...

DrJ;
Thanks for the heads up on the corrosion picture. I wonder if I can get a cst iron neck with a threaded connection for my temperature gauge like the chrome one I have now?

Yes you can. Trot down the the local parts store and look at their Buyer's Guide for heating and cooling parts. If you have a Chevy motor, there are lots to choose from, and almost all Chevy's are interchangeable, big block, small block, even most 4 and 6 cyl. Some even have 2 threaded holes in different sizes. Take your pick. Just make sure you pick one that's pointing the same direction as your old one.

bjb
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There's a world of difference between "good" and "good enough".

After replacing yet another leaking housing came up with a so far still working solution. Found myself couple hundred miles away from home on a sunday and not a part house in sight. Dam leaky Taiwan housing that seems to find themselves on many a SBC. Only solution that day was some 2 part epoxy. cleaned the housing as well as could be accomplished with a scrap piece of 80 grit then mixed up a generous amount of epoxy {5 minute type} the coated the inside as thick as the housing would hold. Its been over a year now and its still holding. Maybe not super trick butit did get me home and a lot further.

Stoke,
I replaced a leaky chrome thermostat housing this spring. I ordered a new one from Jegs. I too installed this on an aluminum intake. The one I got from Jegs leaked right out of the box. There was a pin hole in the casting. So, I sent it back for another one. This one has been on ever since, and not a drop has leaked.

Here are my observations from my experience:
1) You may have to try several before you find the "right one"
2) Identify the location of the leak. Mine was at the crease in the neck, not at the mating surface
3) I used an o-ring gasket, and high temp copper silicone. No leaks yet.
4) Don't over torque the bolts, you could crack or warp the aluminum.

Hope this helps,
Bob

I find you should do the belt sander trick on all flat surfaces before install.Heck we even do water pumps and intake manifolds.You will not believe how many of these NEW parts are bad.Also use a big file on t-stat opening in the manifold.Black silicone seems to be the best choice.Never really seen the chrome t-stat housing errode that quick(WOW) but we use antifreeze up here with over a 50% mix. One last note ,watch the bolt length,last week a customer car came in with bolts on the t-stat that were just a little to long(the silcone in the bottom of the bolt holes plus NO washers) let the bolt bottom out.
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If you have to trailer it, leave it home!