This is the method I used to fix my situation: Thermostat housing was leaking like crazy so I kept tightening the bolts, thinking it would solve the leak, ended up breaking the bolt and now I had a broken bolt and a leaky thermostat. To remove the broken screw/bolt I had to make a tiny hole on it using a cordless drill and some very small drill bits, used penetrating oil as lube and after a good hour or so of drilling in incremental sizes (1.5mm, 2mm, 3mm) I was able to create a little hole big enough for a reverse drill / broken bolt extractor to fit in and get that pesky broken bolt out of there. From what I gathered researching for this issue is that these leaks are definitely caused by the previous gunk/rust residue creating an uneven mating surface between the block and the thermostat housing/gasket. To clean it off I used a razor to remove the chunky residue, very carefully not to scratch the metal, and then I used wet sandpaper grit 500, 1000, 2000. Doesn't need a lot of sanding just enough so that the surface is smooth, doesn't need a mirror finish. Give your new thermostat mating surface a quick little 2000 grit sanding as well just in case. And then clean both surfaces with a little bit of alcohol and let it evaporate, make sure its bone dry. After I used an RTV or Gasket Maker, and put it on the mating surface, just a little bit all around, it really doesn't need much at all, just enough to make a thin film and I installed the new thermostat and housing by hand tightening the bolts, afterwards waited at least 24h before torquing to final specs. Some RTV are different and you don't need to wait, it should say on the box. About the torque, you're better off seeing what grade and diameter your bolt is, and searching online the recommended torque values for it, because my car's torque sheet was a bit confusing and originally I ended up torquing 20nm on a bolt was supposed to be 10.5nm (8.8 grade 6mmx16mm bolt) which caused the broken bolt in the first place. So be careful with the torquing and look up the bolt specs and torque before properly tightening it. And it worked, no issues so far!

It makes sense! My bolts are rusted, I cleaned them up good before reinstalling but did not clean the holes; I'm getting a leak from my thermostat housing. I'm going to the hardware store for some new bolts right now. Thanks for the info!

I have been fighting this problem for awhile now, going to try this. Thanks

The issues with a thermostat housing is just two bolts to fasten it to the engine. Three fasteners would be more stable and more beneficial with sealing.

Thanks! I got the same problem...will try this.

Good job on this video. Useful.

Thank you!!! This was my issue!!!

Great upload helped a lot!

Having the same issue right now! I'll try this to see!

Good tip thank you!

Thanks for the video. My 91 Ford e350 was overheating so I switched out the thermostat( resent purchase and didnt know maintenance history) which was covered in rust. When I put it all back together and drove her around the neighborhood I started getting coolant leak out of the thermostat housing. Thought maybe I put the gasket on wrong but now I'm wondering if all the rust around the bolts is the culprit. Will check it out:)

Yea this make sense I cleaned both the holes out pretty good for the bolts, but shining my flashlight down in them I can still see crap. I couldn't even get it all out with the compressor. I used a bunch of rtv and that sealed it up better because the gasket that came with my housing is pretty crappy too. Added some more washers and that made it better, but it's still seeping a tiny bit so gonna take it back apart use a new gasket and go ham on the bolt holes. Due to the stupid location of the housing on the 2nd gen I couldn't even get all the old gasket off considering how much everything is in the way. Got most of it, but I'll give it a try again tomorrow after letting everything get hot then hopefully the rest of the material will come up.

I'm having this issue now on my 3rd attempt and Gasket- going to buy a new housing and sensors while in there - never cleaned where the bolts go , just the bolts... I replaced gaskets before and never had this issue

U just saved my truck

Will the thermostat work without a gasket or a home remedy homemade gasket like a tube glue like sealant work??? THKS

Good video

Can you just retap the holes then add a solvent to the bolt holes to dissolve the rust, retap again, then blow the holes out?

Do you know how long so it can dry?

I see mine leaking, right? Okay... coolant is still leaking downside the back of the motor on to the ground. Question- do you think it’s the coolant running downside the intake manifold and dripping down. Or is it the intake manifold itself. Obviously I see the thermostat housing leak from standing & looking down at my car.

How long u wait with sealant to drive

Do you need to remove the engine to insert the bottom bolt on a thermostat housing