Ok, so I'm not a professional mechanic, but I'm not exactly incompetent, either. Did a coolant replacement, flush, new thermostat, you know, all those great things. My challenge is getting the dang thermostat housing to quit leaking coolant! I've reset this thing going on 6 times now. I've tried with and without gasket(including the sticky kind), using permeated gasket maker, everything! I know it's tricky because it has to be seated in the housing perfectly. I am thoroughly cleaning the housing and the engine face, to make SURE that isn't the problem. Anyone have some hints on how to make a great seal!?

 

It really shouldn't be that difficult. Are you sure your bolts are screwing in far enough? I would screw them in without the housing and make sure. I'm sure you made sure the thermostat fits in the groove in the housing?

I like to use the blue colored sealer in a tube along with the gasket.

A little trick to hold the thermostat in place. Use some twist tie material, like on bread wrappers, and hook it on the bail of the thermostat and use something to bridge across where the hose goes on the thermostat housing. Twist the twist tie tight and you don't have to worry about the thermostat falling out of place.

 

I'm using the same bolts that I took out of it. The thermostat fits in the groove seat for the housing. I actually used the same trick as you mention, but used safety wire and tied to a bolt to twist and tighten in place, then once installed I simply cut the wire and tit easily pulled out. I've tried the blue permatex , thermostat gasket maker, even "the right stuff."
Frustrated. I'll do it again and take photos to document my steps.

 

Good trick for the thermostat.
For a gasket, after making sure both the block and housing are cleaned up really well, I glue the gasket to the housing (makes it easier to clean off next time - take it to a workbench) then put a liberal coat of automotive grease on the gasket - the side that contacts the block - and that's it. I've never had a leak.
And next time you want to change the thermostat, the block cleans up easy and the housing can be taken somewhere convenient to clean the old gasket off and get a new one set up.
Actually I have a spare housing, so the job gets done in 20 minutes, clean the gasket up later.

 

Holy sh**. I'm doing mine today and I have the same EXACT problem! I was sooo frustrated and kinda getting nervous that I broke something else. I had to buy a racheting box end 1/2 wrench to get into that bolt. And I noticed it was still leaking. Like you, I said, f it, remove everything again and lo and behold, I did notice the thermostat was not in the housing perfectly, it would slip down as you put it in.

Looks like this:




Super tiny gap as it slides down.
I tighted it before and noticed that gasket is now messed up. So now I need a new gasket.

Please experts, chime in with all your tips to center this darn thermostat.

Ohh, also noticed, whoever did mine before put it in backasswards

 

And roger! I'm starting to think I have another problem, but perfect timing as my thermostat change? Unlikely. Here's picks of my housing just cracked open.

 

Here's the engine. Looked like perfect set and seal to me! Hells bells, had to use a wrench to pry off the housing! I picked at the "Right Stuff" gasket and I just can't figure out where it got through at. This is frustrating.

 

I hear ya man. I'm done for today. It's V-day so gonna spend some time home. Leave that truck out at the car port for now. Gonna lock back at the thread for some more tips. I think that gooey stuff on the thermostat and let it sit and then the gasket. Then put housing in, then maybe pull it from the housing to recenter?

 

Meh, I tried that before and was unsuccessful in keeping it centered. I know some of those gasket makers need to setup a while before putting it back together. I plan on following the advice of the guy up a few posts (Chris-1) and glue gasket in and grease up the other side. Sounds logical. I've got a sticky gasket but still gonna take my time, cleanup old gasket, dry both sides, etc. more to follow...

 

Okay, I was watching "Better call Saul" on Netflix and I'm so much better and fixing things when I'm not fixing things. Here's what I did with a string and a pencil. I still need a new gasket. Will do that tomorrow, hurray for presidents.

I twisted string on th epencit, and twisted it around til it was tight. Pulled the thermometer into the housing. So I figure, gasket, screw it in, pull out string.