Thermostat housing keeps leaking.

[TreySC]

Hope this is the right part of the forum. I got an '01 B3000 about a month ago test drive was fine drove it a bunch the day I got it until that night it overheated I pull over and it's spraying coolant from around the t-stat. I replace the t-stat and figure out the last person to do it used the paper gasket and RTV, so I'm thinking that's the issue. But for some reason it never felt like the coolant was flowing through the hose to the t-stat.

I got fed up and took it to a shop to make sure I didn't do something wrong and have them give it a once over for any other issues. They did a pressure test and everything was fine, but they said the heater core was clogged. I decline to have them replace at $900 and figure I can do it myself. When I get it home from the shop the t-stat housing is leaking again! I do some more research on it and I'm pretty sure I didn't tighten the bolts evenly and hope it just needs to be resealed. I end up having my neighbor help who is a self taught mechanic, he's usually super busy that's why I didn't ask him before.

We get it done this past weekend, new heater core, t-stat housing resealed. Once we get the main part of the dash in place we fire it up to make sure everything is working. Air and heat perfect, doesn't run hot, no leaks. It's a little over 90 degrees so we let it run with the a/c on while we finish putting all the trim pieces back together on the dash and whatnot. After sitting there running 30-45 minutes, no issues take it for a little drive everything is great. Made a run to the dump later that day the temp started to climb a little but it settled down and was fine.

Yesterday I drive to work, go to the store at lunch, go to my kids football game no problems. Come home from the game and something smells funny, I pop the hood and the dadgum t-stat housing is leaking again!

I guess my question is could the housing itself be bad? Should I try a regular gasket instead of RTV? Or is there something else I might be missing that is causing this. Sorry for the long post just wanted to get all the info in case it helps.

TL;DR Overheated, replaced thermostat, resealed twice, keeps leaking, driving me crazy.

 

[Curious Hound]

Is it just leaking from where the housing bolts on? Did you get the mating surfaces clean?

I had trouble one time and found out it was self-induced. I put the gasket and thermostat in the wrong order. It wouldn't seal that way. If I recall, the thermostat goes in first, then the gasket on top, then the housing. There is a shallow recess that the the thermostat fits into. Then the gasket goes nicely between the mating surfaces when you install the housing. I definitely recommend the gasket. They're cheap. I usually keep several on hand. A light coating of rtv is ok but unnecessary. That just makes it harder to clean next time.

Also, might want to inspect your housing and make sure it isn't cracked and make sure your hose is in good condition so that it seals to the neck properly.

 

[TreySC]

Yes it's leaking there. When I did it I made sure it was all clean, I assume my neighbor did when he resealed it. I guess I'll try the regular gasket and give the housing a thorough inspection.

 

[helpme]

Not sure about yours but my housing has a small indentation that the thermostat sets in. To keep it in the housing when you're putting it back on , you use a small piece of wire with a hook on the end to hook over the top of the thermostat. Then hook the other end of the wire over the edge of the outlet portion of the housing. It stays together till you're ready to put the hose on. Then unhook the wire from the assembly when you put the hose back on. Of course replace the gasket, sealant.
You most likely had the lip of the thermostat incorrectly placed under the flange of the housing thereby causing the leak. You might need a new thermostat if it is too bent.
What I do is leave the hose off the outlet and fill the radiator until I see it coming out of the outlet. Then I replace the hose and refill the rest of the way. Good luck!

 

[TreySC]

So an update, With kids games and practices I don't get much time to work on it and thankfully my Dad has an extra car he's letting me use.

Tried to go just paper gasket on old t-stat housing it leaked an SOB just driving it up the road and back. Get a new housing, and in the process of putting it on I cleaned a bunch of old rtv out of the bolt holes. I get that all buttoned up and while refilling the coolant I notice one of the heater core hoses is leaking where it meets the engine and spaying all over the t-stat housing. Replace that hose last night go on a little test drive everything is good.

This morning had a kid miss the bus when we get to his school and park I hear a little pop and it's puking coolant, turns out it's coming from the overflow tank. Thankfully the school isn't far from the house so I drive it back home and switch vehicles. On the way back when I would stop the check gauge light would come on but the temp needle never went past normal range.