Dumb Question About Thermostat Housing

I keep breaking the thermostat housings when installing. Right at the front tab at the bolt holes. At first, I thought it was the old crusty aluminum housing that was on there just being brittle. Now, I just broke the replacement which is steel. Same place.

I was told the torque for the thermostat bolts was 22'lbs. I'm very careful to step up the torque while working around the bolts in a circle.

I installed the replacement housing a few weeks ago and used permatex grey, a diy gasket kit, and only tightened it to say 15'lbs which help up nicely.
Last night though I decided to change my thermostat to a 180 from a 160 and figured I'd try again to hit the 22'lb mark..... snap.

Am I crazy about this being the recommended torque?

The surface of the thermostat was perfectly flat. The mating surface on the engine, not so much. Meaning its 60 years of crust and pitting. But nothing super obviously raised or lower. I sanded the surface and its as flat as i could get it but I'm still worried I'll break another housing when it gets here.

I ordered 2 just incase.

I've got a really dumb question that might answer my problems:
Does the gasket go on the engine block and THEN the thermostat on top of that? Or does the thermostat get sandwiched between the engine block and the gasket with the housing riding on top?

Also, I noticed the housing itself kinda squashes the thermostat and holds it into the little ridge in the engine block, should the center hole of the gasket be the same diameter of the housing (meaning the gasket rides on top of the thermostat body)? Or should I cut the center hole to be the diameter of the cavity in the engine block, which is much larger? That way, the gasket never touches the thermostat itself and the only thing touching the thermo would be the engine block on one side and the housing on the other. like a sandwich.

Does this make sense? I'm thinking the height of the gasket sitting on or under the lip of the thermostat might be raising up the bulk of materials so high that the thermostat needs to bend in order to seal and then breaks.

Please advise if possible.

 

"Sanding" does not make a surface flat, only sanded. Use a straight-edge such as a file.

Checked your torque wrench for accuracy? Or compared with a "known-good" wrench?

Pro-Tip...way easier to get clear answers to just one or two questions at a time.

 

Don't know which engine you have, but there should be a small recessed area either on the engine side or in the thermostat housing that the thermostat sits into.

 

Yes indeed there is!

f134 engine. The recess is on the engine side.

I guess a more poignant question is whether or not the gasket needs to go "around" the thermostat (meaning the holes is larger than the thermo). Or go ontop of the thermostat and help sandwich the thermostat to the engine block.

I seemed to remember the latter. which is why I cut the center hole to be the diameter of the inner housing. But I'm wondering if this caused there to be too much thickness in the center.

Unless I'm missing something much more obvious that could keep causing it to snap.

 

Haven't checked the torque wrench against another since it's my only one. hmmmm.... Its never been a problem before. Only on this particular part.

I sanded just to make sure I got rid of any ancient gasketing/sealing material left by PO's I checked for ridges and valleys using a straightedge and a flashlight.

 

I suspect this may be the problem. The thermostat does not need a perfect seal.

 

Ok cool. I'll try a larger hole in the gasket center.

The new housings should arrive tomorrow.

 

Thermostat fits inside that recess. Gasket installs over thermostat. Never mind the big hole size. Just line up the bolt holes in engine to gasket. Carefully place housing over gasket to not move gasket. Cinch up bolts. Done. Beer thirty.

 

Thermostat goes in the recess, gasket goes over.

Take your sandpaper and tape it smooth side to the better surface, sand a little. Reverse the sandpaper side and sand the opposite surface. It doesn't have to be flat but simply match each other.

Take your gasket and put it in the recess.
Put a thin layer of rtv on both sides of the gasket and put it over the thermostat then housing on that. Put bolts in and tighten just enough to squish a thin amount of rtv around the parameter then leave it alone overnight.

 

torque wrench
I just do the does it feel tight
on anything but heads
as to gasket . the gray stuff works great without paper gasket

 

Identifying the cause of the breakage, so as not to repeat is the battle.
In your case as others have stated that recessed area is home to the thermostat, clean that recessed area completely, so the thermostat seats properly, if it sits even slightly off, then tightening it down, will break that thermostat housing.
You got this.

 

Thx guys! the recess area was definitely pitted/crusty/and uneven. I got in there with a chisel and carefully scraped out decades of corrosion and now it seems to set in there a bit more evenly.

This makes sense. You guys are all so helpful thank you!

I cut out the center hole of the gasket to sit around the outer perimeter of the thermostat and now when I set the old housing on top of everything, it seems to sit flush. I can even reach into there from the top and wiggle the thermostat the tiniest bit so I know the housing isn't sitting/wobbling on it at all anymore.

Will update after the new housing gets here. hopefully with good news!

 

Now I could be wrong. Was wrong once before (well actually I thought I was wrong but was mistaken).

As I advised, nevermind the hole size of the gasket. I have NEVER cut the hole bigger. AFAIK, the gasket is supposed to press down on the 'stat.

 

It'll be ok. Don't keep him up all night thinking about it.

 

I didn't sleep... Just kept waking up and crying out "THErmOSTAAAAAaaaaaTTTTTTT"!

I Got the new unit installed. When It arrived It had a blob of slag right on the front ear/screw hole so I ground that off to avoid any more problems. Installation went well! I chickened out and didn't go more than 17'lbs but I just tested it for about 20 mins and all seems to be holding and working well!!!! I used Permatex grey on both sides of the gasket.

Thanks for the help everybody!

 

I think 1 1/2 uggah duggah's is correct torque.

 

I forget how large those bolts are, but they are probably at least 1/4-20? I would think that could easilly take twice the amount that broke it. Sometimes you win, sometimes you lose, haha

 

Torque on a grade 5 1/4-20 is something like 6-8 ft/lb. I think a 5/16 course would be in the 14-17 range. Different charts will give slightly different values. If they are 1/4-20, you are over tightening them. I keep a chart in the garage because although I’ve been wrenching on my own junk for 30 something years, I continue to surprise myself how light a torque fasteners really take.

Tim