Technical Thermostat housing sealant, what works?

RTV has always been a way to deal with an imperfection in mating surfaces to me, or to glue a gasket in place lol. But the gask a cinch stuff works best for that these days. But when I use rtv, I generally use the gray stuff. I think the blue is considered traditional though. Traditionally dug out of radiators and oil pump pickup screens

 

I guess I'm always hesitant when something is good for exhaust thinking it may not be good for coolant. I appreciate you letting me know that. I may try that stuff.

 

What I don't like it squeezes out you see it on the outside but it does the came in the inside and maybe comes loose and goes somewhere you don't want it. Especially if it is in the oil system down stream of the oil filter.

 

I rarely use any. Used to stick them on with grease. Rarely, if ever, had a problem. Factory used nothing.

 

and fuel tanks and carbs....guys use the***** everywhere! ugh

 

Blue and red RTV are a sure sign John Barleycorn has been working out in the barn

 

Is the thermostat body itself fully seated on the intake manifold? I ask because I ran into a similar issue not long ago on a 4.3L V6 and it turns out the little copper pellet pressed (loosely) into the t-stat body would not allow the t-stat to fully seat, though it was very close. Never had that happen before, so I flattened the pellet a bit more and no issues since. Don't forget the anti-seize on the bolts!

 

Take a good flashlight, tighten down the housing. With the light shining in the neck of tge housing, see if you have an light coming out at the sealing surface. Do this without a gasket. As mentioned several times before, it may be warping when snugged down.

 

That wouldn't be Billy Joe Bob Dingwhistle's cousin would it?

 

Unfortunately I know all too well that the factory used nothing. It resulted in a lot of leaks on this particular engine which I'm trying to avoid going forward. The factory didn't even use exhaust gaskets. It worked for a while.

 

Good idea.

 

Gotcha. Good luck.

 

Everywhere else I used the Ultra Grey I was very careful to not put very much. I wanted it as insurance to the gasket, not to smear everywhere and make a mess. On a Buick the front cover houses the oil pump, distributor, water pump, and fuel pump, so sealing is very critical. On the thermostat gasket I put a thin layer, just as insurance. Didn't work there. Didn't have any leaks anywhere else but I haven't had it running long yet.

 

Hmmmmm ... are you****embling, snugging the bolts, letting cure then tightening the housing bolts or are you****embling, tightening the bolts then letting it cure?

Your leak doesn't make sense.

Two flat surfaces with a gasket and sealer don't leak. Snugging, letting cure then cranking them down, tweaking the housing and tearing the already cured sealer does ...

 

Yeah it is. It's a big flat surface. Isn't it fun taking the gamble on whether parts will be made correctly these days?

 

Yup, married the same sister....

 

Plus one for Yamabond. That stuff is magic.

 

Sand the housing on a flat surface
Black spray paint on the gasket
Install while the paint is wet.

 

This is one sealant that was recommended to me years ago. Like most, it does not take much.

Amazon.com: Permatex 25228 The Right Stuff 90 Minute Black Gasket Maker, 3 oz, 1 Count (Pack of 1) : Automotive

 

Without reading every single post...has anyone mentioned the bolts bottoming out in the intake?

 

they didn't bottom out before he worked on it, apparently.

I've used The Right Stuff a couple times in my life, it seems you only get one use out of a can, though.

 

The area between 2 pieces of flat metal to be sealed should do so with a dry gasket.
"a shaped piece or ring of rubber or other material sealing the junction between two surfaces in an engine or other device."
Any further sealant is to allow the gasket to settle into place during installation and fill any imperfections in the surfaces or a gap caused by uneven clamping tension. Back in tech school, the instructors would require using white lithium grease on paper or cork gaskets, because it was easier to take apart the student's mistakes.
Using any additional sealer is due to added stress, like liquid, pressure and temps, all of which are present on your application. I'd check with the guys that make the products for what they recommend.
This is one page of Fel-pro's website, there are other tech pages.
https://www.felpro.com/technical/field-test-garage/use-and-misuse-of-sealers.html
Here is the permatex page for help.
https://permatextraining.com/
Jim and others answered with more than asked because he's done the job many times and wanted to cover all the solutions to what is a common problem. This type of communication (forum) often sees people who ask a simple question, then after more back and forth describe a much more complex question. Your replies do not prove that your knowledge and experience are formidable, rather that you are ungrateful to any free help that does not meet the exact form of your query. So, to help you, just refer to the bold section and ignore the rest.

 

I have run into this a few times. Rad caps are not 7lbs, when alot of old engines were designed.

Aviation Permatex - @always better than RTV.
I believe OEM housings work better.
I like cast iron if I can find one. Just put one on my 402BBC with permatex and no leaks. 10lb cap.
Possibly the biggest challenge is " Patience" I'm guilty of not waiting for sealant to skin, cure before subjecting to pressure, temps, coolant.

Chrome water necks.....he'll no, like chrome oil pans, nothing but trouble.

Cold water leaks are the hardest... IMHO. I have a Kubota tractor, only leaks around 22deg F. Colder, Hotter, no leak. Leak is under after treatment, fuel lines etc... can't get a mirror in location.

 

My two cents worth! Take a mill file and rub it across the mating surface of the thermostat housing to ensure there are no high spots. The goal is not to remove a lot of metal just to make sure the surface is clean and flat. Clean the surface well. Apply RTV to get a uniform layer maybe .030 thick smooth it out with a coffee stir stick, old credit card, finger, etc. Put the thermostat housing in place start the bolts and draw down bolts just enough until you see the RTV just start to squeeze out of the joint. YOU ARE NOW DONE FOR SEVERAL HOURS! Once the RTV sets torque the bolts down until tight. The theory is torquing down before RTV sets just squeezes the RTV out of the joint. I’ve used this on engine parts, body parts, sailboat hardware, household repairs, etc. without leaks. You mileage may vary!

 

One thing to try may be to clean the housing well. Color the mating surface with a magic marker or a light mist of primer. Put a sheet of 240 wet or dry sandpaper on a flat surface or a thick pc. of glass then do a couple passes with the housing. That will tell if the housing mating service is flat. If it is slightly off then carefully continue on the sand paper until it is flat.

 

Only took over 70 posts for the OP to let the cat outa the bag that the engine might be a Buick of some kind??????
Must be one that's not Hamb friendly.

 

Think what you want. The reason I'm not sharing is because it's irrelevant. I asked a specific question and it took many replies for people to not be focused on something else.

 

Accuracy vs precision. If you get 10 answers to a question that are the same they must be good, right? But if they're not the answer to the question you asked you aren't any closer to solving it. I don't need to prove my knowledge to anyone here. As I said, I was looking for answers to a specific question, which I eventually received. Yes, you're right, I wasn't looking for free help that wasn't answering the question I asked. You seem to think that's unreasonable. I guess we'll disagree.

If you see the progression, the other guys eventually came to the same conclusion that it was the sealer used after going around through all the hoops.

 

I didn't put the rad cap on. It was leaking with the rad open under water pump head.

Funny the stuff still isn't cured now. I'll see if I can find some of the non rtv suggestions.

 

I thought of that, but wasn't going to mention it. Let him figure it out himself.