thermostat woes

tsiemens · Feb 2, 2020

This thermostat housing is driving me crazy and good thing these gaskets are cheap. I've had 3 different new gaskets in this thing already and it leaks every single time out the bottom. I cant even fire the old 5.0 up. Twice I've used red rtv and once silicone spray. Always leaks as soon as the coolant level reaches the bottom of the housing. Any suggestions? How much torque should these bolts get?

Thanks!
Its my old 86 5.0

OldManRiver · Feb 2, 2020

The only time I've had one leak is when the thermostat slide down and got pinched between the housing and the block.
Use rtv on the thermostat to help hold it in place in the housing,letting it dry so it stays in place.Since most housings are pitted,I've always apply a thin amount of gasket maker on both sides of the gasket.
If this is the way you've done all the installs then I got nothing else.
Good luck

Potomus Pete · Feb 2, 2020

I may be wrong but I had a leak on my trucks thermostat and the only thing that sealed it was a special rtv that was made for antifreeze. The fluid kept going thru gasket maker. The parts store has it and it says its for cooling system-antifreeze.

Potomus Pete · Feb 2, 2020

Permatex for waterpump and thermostat .5 oz

JD1964 · Feb 2, 2020

OldManRiver said:
The only time I've had one leak is when the thermostat slide down and got pinched between the housing and the block.
Use rtv on the thermostat to help hold it in place in the housing,letting it dry so it stays in place.Since most housings are pitted,I've always apply a thin amount of gasket maker on both sides of the gasket.
If this is the way you've done all the installs then I got nothing else.
Good luck

Ditto...glue the T-stat in place in the housing with a small amount of rtv and let it sit overnight. Then a light coat on both sides of the gasket and the mating surfaces. Let it get flashed over like its beginning to set, then install. After that I usually let it sit overnight again before I fill it up.

revhead347 · Feb 2, 2020

If it's the original aluminum one, it's likely warped. They suck. Go to Advance or Autozone and ask for a "water outlet" for your car from the parts guy. It's like $11, and made of cast iron.

Advance Auto Parts - Down for Maintenance

These never warp, and last forever. Best $11 you'll ever spend I guarantee it.

Kurt

tsiemens · Feb 2, 2020

thanks for all the advice I'll update soon

tsiemens · Feb 2, 2020

I have to say theres a strong possibility the thermostat is sliding down as mentioned

JD1964 · Feb 2, 2020

Also make sure you get both gasket surfaces free of all previous sealer and gasket material. One little chunk of stuff left on there from before can prevent a good seal.

90sickfox · Feb 2, 2020

I had an issue once and found out coolant was leaking past the bolt threads. I use " right stuff " on my thermostat housing and use a little to stick the thermostat to the housing as mentioned. I don't even use gaskets anymore...just the Permatex. If the holes for the bolts pass into the water jacket I apply a little to the bolt threads too.

General karthief · Feb 2, 2020

To check the mating surface on the housing take a piece of sandpaper on a flat surface and rub the mating surface of the t state housing a few times that will show you how bad it is.

96pushrod · Feb 3, 2020

90sickfox said:
I had an issue once and found out coolant was leaking past the bolt threads. I use " right stuff " on my thermostat housing and use a little to stick the thermostat to the housing as mentioned. I don't even use gaskets anymore...just the Permatex. If the holes for the bolts pass into the water jacket I apply a little to the bolt threads too.

I rarely use the t-stat gaskets anymore either. A little bead of ultra black is usually all I use. Never had one leak.

+1 for attaching the thermostat to the housing with rtv.

revhead347 · Feb 3, 2020

tsiemens said:
I have to say theres a strong possibility the thermostat is sliding down as mentioned

Yup, and the first time you crank the bolts down after the rim of the thermostat has dropped down, you bend the factory thermostat housing, and it takes a miracle amount of RTV to seal it, if it will ever seal. It's something that almost every Mustang owner has done. I remember bending my first thermostat housing.

I use gasket tack on all my gaskets. First I tack the thermostat into the housing, then tack the gasket to the housing. Let it set up for a few minutes, then move it around to ensure the thermostat won't drop out just by moving it.

Advance Auto Parts - Down for Maintenance

Kurt

revhead347 · Feb 3, 2020

90sickfox said:
I had an issue once and found out coolant was leaking past the bolt threads.

Also a valid point. Those bolts should have a little bit of teflon thread sealant spread on them before they go in.

Advance Auto Parts - Down for Maintenance

Kurt

dcm0123 · Feb 4, 2020

Had a problem with a new aftermarket cast iron housing a couple of years ago. Check to make sure the holes line up properly with the gasket before you install it.

OEM ones crack very easy, check your for cracks.

For what its worth Permatex makes a special gasket sealer for coolant. They do not recommend the others sealants for coolant. Most auto stores carry it.

Would be a good idea to use an adhesive to hold the thermostat in place. I sometimes use Permatex #2 between the thermostat and the housing to hold it.

Gs1987GT · Feb 6, 2020

As mentioned, use blue rtv, a very thin amount, both sides of the gasket and on both bolts just for precaution. The rtv will hold the thermostat in place, but yes,, access is limited and it's a bit of a pita to get right.

Stick with it, you'll get it. Lots of great advice in this thread

waxman · Feb 8, 2020

drill a small 1/8 in hole in the stat to let the air out that might be in the system

Blown88GT · Feb 8, 2020

Ford Performance might still have their chrome plated machined aluminum t-stat housing.

revhead347 · Feb 8, 2020

Blown88GT said:
Ford Performance might still have their chrome plated machined aluminum t-stat housing.

I've installed one. I was not impressed with the quality. Like the blue "performance" radiator hoses everyone had to have. Those things always leaked.

Kurt

tsiemens · Feb 9, 2020

I bought a new outlet which came with a new gasket. Used rtv to keep the stat from sliding out of place then I put more rtv sealer on both sides of the new gasket. I can see the stuff has squeezed out all around the outlet. Its just sitting now because the rtv stuff says 24 hours before adding fluids. Lets hope it works this time or its getting towed in the spring when I can get it out of the barn.

thermostat woes

tsiemens

my welding skills arent really skills

OldManRiver

Active Member

Potomus Pete

I'm still waiting for the fully nude shots

Potomus Pete

I'm still waiting for the fully nude shots

JD1964

there is enough sticking out to grab on to

revhead347

Apparently my ex-husband made that mistake.

tsiemens

my welding skills arent really skills

tsiemens

my welding skills arent really skills

JD1964

there is enough sticking out to grab on to

90sickfox

Wasn't a pretty sight...and I've got big hands

General karthief

wonder how much it would cost to ship you a pair

96pushrod

I think they're a little easier to get off

revhead347

Apparently my ex-husband made that mistake.

revhead347

Apparently my ex-husband made that mistake.

dcm0123

Gs1987GT

Active Member

waxman

Blown88GT

revhead347

Apparently my ex-husband made that mistake.

tsiemens

my welding skills arent really skills

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thermostat woes

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I'm still waiting for the fully nude shots

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there is enough sticking out to grab on to

Apparently my ex-husband made that mistake.

my welding skills arent really skills

my welding skills arent really skills

there is enough sticking out to grab on to

Wasn't a pretty sight...and I've got big hands

wonder how much it would cost to ship you a pair

I think they're a little easier to get off

Apparently my ex-husband made that mistake.

Apparently my ex-husband made that mistake.

Active Member

Apparently my ex-husband made that mistake.

my welding skills arent really skills

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