Thermostat housing leaking

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olddman

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Have a 1965 Dodge Dart GT with a 273 V8. Can not get thermostat housing to stop leaking. Have changed out the housing and tried both bought and home made gaskets. Tried different gasket sealants, but water still leaks at gasket. Does anyone have solution to problem?
 
Make sure both sealing surface are flat. One could be warped. Try a cast iron thermostat housing. Make sure you are using a thick paper gasket or try Permatex The right stuff gasket maker by itself.
 
There was a post on this a week or so ago. Search. That case had an aftermarket aluminum intake. Several suggested the problem were the extra holes that sit in the middle of the gasket. Same for me, I put in a setscrew and RTV to make a flat sealing surface. No more leak.
 
I've found the older cast iron intakes pitting purty bad at that mating surface.
Decking the housing with sand paper on a flat surface can help.
If you use a silicone gasket maker product with or without a paper gasket. Give it plenty of time to cure.
 
Thank you all for the suggestions. Have tried doing what you said. I made another
gasket out of thick paper. Put Permatex on the intake and the thermostat housing.
Reassembled this morning and leak was still there.
This problem started last fall, up until then no leak. Pulled thermostat off and put flat edge on it. Looked a little uneven so I got a new one. It is a chrome steel housing. Had same problem with new housing until I made a gasket, put Permatex on the intake and the thermostat housing. Let set over night and assembled the next day. No leak until last month.
Anymore ideas as to what to try next?
Thanks
 
put it together then let it set up overnight before you run water through it otherwise one of the surfaces is not flat
 
I usually let the silicon "cure" for a couple of minutes before sticking it together. Waiting a while before running water through it is good advice also.

Not sure how it works on the cast intakes, but a lot of the aftermarket intakes don't have blind holes for the bolts, meaning they go through to the water.

I once had a leak I couldn't figure out until I put some teflon tape or TFE paste on the thermostat housing bolts. Now I do it every time.

If your bolt holes go through to the water, this may help.

Good luck

Steve
 
Just to be sure, confirm the Leakl is not coming from the hose/housing mating.
 
Permatex an O-ring on one side. Torque down until you see it squeeze to about 1/2 its original thickness then stop. If it holds, then put sealant on the bolts and do it again. No cracks in the casting is there?
 
I use gasket sealant on the gasket and bolt threads. It is a sticky purple gel that stays soft. It cleans up with alcohol. I also used a thicker paper gasket that came with another thermostat housing I bought (~$12 ebay, looks like stainless), but I used the original chrome housing since it looked fine and flat. Some say the chrome plated housing always leak, but I haven't heard a technical reason why.
 
I got my copy of Mopar Action three days ago. It has a story about a system using O-rings. Have not read it yet or know how much it costs. May be another way to go.
 
Denvermike said:
I got my copy of Mopar Action three days ago. It has a story about a system using O-rings. Have not read it yet or know how much it costs. May be another way to go.
Click to expand...

I went to the web site terrysautolab.com $99.00 but looks like a fix!!
 
360904 said:
I went to the web site terrysautolab.com $99.00 but looks like a fix!!
Click to expand...
Please tell me that gasket doesnt cost $99...!
Mopar prior to 78 used the Chevy bolt pattern, but chevy had the stat recess in the intake, not in the stat housing like Mopar. But they have some cool O-ring housings. Check oout cool-view, Im sure you can adapt that to a Mopar...Just use Dex-cool to keep your engine block Hemi-Orange!
 
Thanks to everyone who sent me their suggestions for fixing the leak. Got the latest copy of Mopar Action and read the article about the fix for this problem. Terry Flebbe of Terrys Auto Lab seems to have come up with a solution for the leaking on 1978 and earlier V8 Mopars. Cost is $99 for the adapter, thermostat housing and bolts. Went ahead and order one today. Will let you know if it works! Again thanks.
 
What manifold is it?
I have an Eddy performer, and it has both Mopar and SBC pattern bolt holes.

What I did was buy the auto parts store Mr gasket SBC "reuseable" silicon impregnated aluminum SBC gasket for $20, and then a new $20 iron housing from Napa, then elongated the holes on the water neck housing using a slide table on my drill press.

I used no additional sealant of any kind.

So far, so good.

I probably could have bought an SBC water neck, and probably used an aluminum one, but I've had terrible luck with aluminum water necks- not on the intake surface, but under the hose in the clamp area.
 
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