Technical Thermostat housing sealant, what works?

Hey guys,

I was putting the top end of my engine together yesterday and when I finally fired it up had a pretty good thermostat housing leak from one spot. I didn't before taking it apart. I used a gasket and Ultra Grey and both sides were clean and dry. Has anyone had good experience with The Right Stuff or another sealant for this type of application?

 

If it's a chrome neck that's the problem, they all leak.

 

Have you checked if the thermostat housing base is flat and not warped?

 

Flat, clean, thermostat centered, gasket, sealer such as Permatex Aviation or #2, no pitting, no RTV, no chrome, no pot metal, no made in China, and it should be fine.

 

Why no RTV?

 

I don't know why, but it's just not the right thing to use on paper gaskets. It also annoys me, when I have to clean it off where someone else used it...it makes an ugly mess.

 

I take a piece of 100 grit sandpaper on a flat metal surface, like the top of a table saw and sand the base of the stat housing flat. Almost every old one is warped a little from the bolts being over tightened.

 

I have a chrome thermostat housing on my A pickup, and it always seeps a little. I've done all the usual stuff with it to seal it up, and it holds under pressure, won't leak a drop when hot; but when the engine cools down and sits for a few days there will be a little seepage around it that collects on the manifold. I dab it with a shop rag and move on. It's not a big enough problem for me to deal with it. The next time I have to remove it for some reason I'll try something else to seal it up.

 

What BJR said. Permatex #2 is not ideal for anything other than cork gaskets. RTV is good as long as you don't glob it on like you're trying to fill up a crack. A thin coat, wiped thin with your finger is all that's needed. THIN, sez me. Don't over tighten the bolts. Check around the bolt holes for cracks, too.

 

If it's the pot metal type from Mr. Gasket, be sure that it hasn't a small pin hole caused by electrolytic action. I use a radiator cap with an anode attached because those thermostat housing seem to get eaten away on my car.

 

yeah it did...we don't know if you have a chrome housing, or one that's made of pot metal, iron, or aluminum. It matters.

 

Of course it did, the question was about leaking thermostat housings, and so was my post. It may not have answered your question, but it was very much right on topic.

 

ok....have fun!

btw if you want more helpful answers, it would be a good idea to provide a few pictures, so we can see what you're working with. Otherwise, we have to guess at what the real problem might be, because you didn't give us all the pertinent information. If you had shown us a picture of a painted cast iron housing, then all the useless comments about chrome, pot metal, aluminum, etc would not be wasting your valuable time, because we'd know that they are not the problem, and wouldn't post them.

 

I didn't ask anyone to read into my problem, I asked for experience on a sealant that works because all else seems to be kosher. That isn't really too much to ask, except this is the internet so I guess it is.

 

Thanks for post #12, and quoting the comment in question, because it preserves the comment, even after the O/P edits it.

It kind of proves the old adage, "You can run, but you can't hide".

 

If you want an experienced answer to a problem. Ask those who have experience with those problems. Then listen to them.
Soon guys like Jim will just turn the page and go on with something else instead of trying to help.
Maybe a big bead of red sealer should stop it.

 

His post was a waste of time. I'm not hiding that. It was a waste of time, it has nothing to do with this thread.

I am looking for an answer to my question so that I can solve the problem, I'm not looking for 90% O.T. responses to a problem. I guess that's my mistake. When someone comments and it has absolutely nothing to do with what I asked, then don't you think that's a bit irritating?

I'm not trying to fill an 1/8" gap. This is a system that sealed when I took it apart. All the components are the same, except for a new gasket. I tried ultra grey and it didn't work. I need to know what does work. Everything is as flat and clean as it is ever going to be. That's not the question.

The old gasket was Fel-Pro, this one is something else and is more slippery. Sealants are literally made for this purpose. It is not a complicated question.

 

I have always used a paper gasket and Ultra Black. I have had a leak on a stock GM thermo housing but sanding both the intake and the housing solved that problem. I also had a leak with a chrome housing ... I sandblasted the sealing surface and solved the leak.

To answer your question ... Ultra Black and paper gasket are what I use.

 

LOL, dude you're a little uptight for a Monday morning, aren't you?

I shouldn't have to explain everything, but here goes.... If you're running an inexpensive chromed housing, as other's have said as well, they are prone to leaking. You may try everything in the book, and yet it may still leak, or like my experience, it may just seep a little as it sits. Which you may be able to live with, or not (you seem to be a bit of a tight****, so I'm guessing not...).

It's not a complicated question, just maybe a little too complicated for you.

Have a nice rest of your day.

 

The problem is that you didn't tell us what kind of housing it is, what engine, what condition the parts are in, etc. We can only guess. And most of our guesses will not be correct, because there is a wide variety of causes of thermostat housings leaking. Most of those causes don't apply to your case, but since we have ZERO information about your case, we have to include ALL the answers that don't apply.

Show us what you got. Then we can help you. Otherwise, your wasting all of our time.

hell, it might be that the correct answer is "NO sealant". Again, that's just an uniformed guess

 

Thank you!

Mine is a stamped steel. I wire wheeled it to remove the old gasket material then cleaned and dried everything..

 

Oh...stamped steel housings like to warp, where the bolts push down. Check it for flatness, you might need to straighten it, which can be difficult...so you might need to replace the housing.

Sealer won't fix bent metal.

 

I should be clear, the factory housing I had that leaked was aluminum and sanding easily trued it up.

 

The overall design of the system makes no difference, though. It's holding coolant pressure between two surfaces. I don't see why you're stuck on pigeonholing it to exactly what system it is. What sealant works to seal a thermostat housing isn't a complex question. Either you've had success with something or not. Heck, I've seen them successfully sealed with clear silicone, and was looking for a better option. The Ultra Grey I used just didn't seem to work.

The housing is stamped steel and the intake is aluminum. Both are clean, dry, and as flat as they'll ever be in the area of the leak. They were literally removed and put back on. I blasted my intake, but I masked off the sealing surfaces with layers of aluminum tape like as is used in the coating industry for industrial blasting. Coolant was spraying out when running on an 1/8" wide area at the top of the gasket (gasket sits vertically). The only thing that changed is I usually use fel-pro and this time my gasket is something else, it's a pale red in colour. It seems like a decent gasket. No sealing surface will ever be 100% flat, that's the reason for gaskets and sealants.

 

It is shockingly flat. First thing I checked.

 

If it's leaking really badly, then it could be the thermostat is not set properly in it's recess. I've done that...it's a****** to get them in place on some engines, such as small block Fords, Buicks, etc.

Again, knowing what you're working on changes the discussion entirely.

 

Very simply, mine is leaking due to pressure in the system, so it starts when you start it. It's not the type of leak that happens when you shut it off. You're talking about a leak starting when the engine cools. I'm talking about a leak under system pressure. Very different mechanisms.

It wouldn't be hard to do with the thermostat mounting vertically, but it was fully in its slot.

 

I did a thin layer of ultra grey. Methinks I'll try a thin layer of something else.

 

According to all you've told us, it should not be leaking. You did everything right, all the parts are correct, and it's****embled correctly. Sealer can help prevent seeping, but it won't stop a major leak. Also, RTV is a good lubricant, which probably isn't what you want when you're trying to seal things?