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!

Good video! Hopefully going to be following this soon.

Thanks for the video. I have a 1978 F250 with 47l60 engine

Hi! thanks for the video, clear and precise to understand. Did you follow the torque spec and what is the torque spec. My housing bolts into a Edlebrok aluminum rpm performer and I had to drill, retap and put in inserts. Thanks

Thanks for posting this. Very useful information and well produced video.

Ended up following it, sadly as a first timer I messed it up a little and the threads on right bolt ended up getting stripped. Appreciate the video nonetheless, if I'd been a little more skilled it would have got me there. One thing for others, if it's cold out I'd let the permatex cure for longer before tightening, and then starting. Thank you for a great tutorial.

GOOD VID. I've noticed on my new engine, (approx 1 year later) coolant doesnt come out, but i see the gasket has coolant which has saturated it (it's those stick on gaskets) obviously ive put on same gasket maker as you. do you recommend me taking it off and seeing what can be causing the gasket to become saturated? maybe it's normal?

I read in Ford forums that you should not run less then 180 deg t-stat. Something about the cylinder walls? Not sure what that is about. FYI

I read not to use a paper gasket with permatex?

Thanx

I see that it is about 2 years since you did this fix. I having the EXACT same issue with a 460 fitted in a 73 Mach 1. Mine has leaked twice now and your video has given me hope. How has it held up? Is it still leak free after 2 years? If not, what else have you tried? I really appreciate any response and help. Thanks!

What did you torque the bolts down to?

Dorman Thermostat Housing 902-1033 Permatex Gasket Maker 765-3017 FelPro Gasket 35041

What causes a thermostat housing to break? Mine did break and the coolant leaked and caused overheat.

Why do you even put that gutted thermostat in the housing? Does it serve a purpose?

Hey dude spraying your housing haz nothing ta do with fixing the leak. Get to the good part keep it simple