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Leaky Thermostat Housing

6

68rt

Well-Known Member
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I recently installed the Mopar Performance alumn. water pump housing on my 440 with the original thermostat housing and it leaked at the thermostat housing gasket. I tried some silicone gasket sealer and it still leaked. I bought a new thermostat housing and again, it still leaks. I check the top deck of the new water pump housing with a machinest straight edge and its straight. so now I'll try a billited thermostat housing. Any suggestions on a gasket sealer??? or anyone had this problem???
 
i just noticed my housing leaking as well. Just ordered a new housing from NAPA. I will keep you posted.
 
I seem to always have some trouble getting the thermostat housing from leaking. Doesn't make any difference small block or big block seem to atleast have one small spot that will drip. I always use felpro gaskets with sealer, and wait 24 hours for it to dry before putting the anti freeze back in. I saw that some one said to try 2 gaskets together. I have never personaly tried that , but I may.
Matt
 
first make sure both surfaces are very clean,suface prep discs on an angle grinder work best.use a good quality gasket(felpro is great).glue the gasket to the water outlet with permatex gasket adhesive(hightac and gasket maker work as well)it will seal the thermostat into place.use either ultra black or right stuff silicone sealer on the housing.speread to an even thin coat(about 1/16 inch)over whole contact surface.alow sealer to"skin up"as stated in directions.assemble,and most important,dont over tighten.i bet it wont leak any more.
 
I used the hard plastic gasket with molded in rubber o-rings from a late model small block Chevy (Sorry, I don't remember the part number) to solve the problem.
 
68rt said:
I recently installed the Mopar Performance alumn. water pump housing on my 440 with the original thermostat housing and it leaked at the thermostat housing gasket. I tried some silicone gasket sealer and it still leaked. I bought a new thermostat housing and again, it still leaks. I check the top deck of the new water pump housing with a machinest straight edge and its straight. so now I'll try a billited thermostat housing. Any suggestions on a gasket sealer??? or anyone had this problem???
Click to expand...

I think your problem is ALUMINUM pump housing with STEEL thermostat housing. Dissimilar metals expand/contract at different rates and are therefore hard to seal. I had the same problem, replaced the steel thermostat housing with a billet aluminum one from Mancini's and problem solved.
 
The steel/aluminum idea could be it, but that's what I've got and in my particular case all is good. I've had good luck with a thin layer of 3M weatherstrip glue on these gaskets.

Just a little sealant is good... too much can cause a problem Like stated before give whatever you use some time to dry before coolant goes in.
 
Thanks to all who replied, I'll give it another go with all your advise. Any others feel free to ad...Thaks Nick
 
Mopars & Missiles said:
I think your problem is ALUMINUM pump housing with STEEL thermostat housing. Dissimilar metals expand/contract at different rates and are therefore hard to seal. I had the same problem, replaced the steel thermostat housing with a billet aluminum one from Mancini's and problem solved.
Click to expand...
Agree. I'm using an aftermarket aluminum housing that is grooved with a rubber O ring. Have taken it off several times to try different thermostats and it doesn't leak a drop.
 
Not to be different...LOL....but I bought an aluminum T-stat housing that I could never get to seal correctly with the aluminum pump...went back to the stock t-stat cast housing on the alum pump and not a problem since!
 
Hello

I just went through this headache, several times. I installed all the air conditioning and got ready to fire it up for the first time and it was leaking like a stuck pig. We actually dicovered a small hole in the original cast aluminum housing. I had a cast chrome housing and blasted the chrome off and sanded out the bottom to make sure it was smooth and flat. Put it all back together and it leaked worse than the one with the hole in it. I bought a cast housing from Brad's NOS. I was going to buy a billet aluminum one but elected to go the heavy duty route. Did the same thing sanded it on a table until it was smooth and my buddy brought over some sealant called the "Right Stuff" in an aerosol can. Put a little on it, bolted it on, filled it up, pressure tested and no more leaks. TA DA.

Just thought I would put my two cents in seeing as I hear alot of complaining about these things leaking. I tried all the good sealants and this stuff is the bomb. Hope you got it fixed.
 
Where did he get the Right Stuff, and thanks for your imput....
 
68rt said:
I recently installed the Mopar Performance alumn. water pump housing on my 440 with the original thermostat housing and it leaked at the thermostat housing gasket. I tried some silicone gasket sealer and it still leaked. I bought a new thermostat housing and again, it still leaks. I check the top deck of the new water pump housing with a machinest straight edge and its straight. so now I'll try a billited thermostat housing. Any suggestions on a gasket sealer??? or anyone had this problem???
Click to expand...
Usually it's the t-stat housing. Did you check that with a straight edge? Either go with the billet one and standard paper gasket, or use the stock housing but have it machined flat. As you can see by all the posts, this is a common problem. Every one I have ever done I run on a belt sander to make sure its flat. They all needed it.
 
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