Thermostat housing problem

1991 XJ 4.0 5 speed manual

OK, I guess this is more me just venting, but if anyone has advice I'm all ears.

So I decided it was time to flush the radiator and replace the thermostat. There's two bolts on the housing, lower one that the belt is kinda in the way of and upper one that goes right through the center. The lower bolt came right out no problems. The upper bolt however decided to stay put and shear the bolt head right off. I can actually twist the housing a little bit which tells me the threads into the block aren't frozen, just the bolt frozen to the thermostat housing. Soooo, I start drilling the bolt out and snapo, my bit breaks off inside and I can't get it out. Soooo, I grab another bit a couple sizes bigger but it won't drill through the broken bit.

At this point in time I figure I am going to have to buy one of those expensive drill-through-anything bits and most likely have to buy a new thermostat housing afterwords since the threads will probably be beyond rethreading.

:bawl:

Spray with penetrating oil, get some sleep. In the morning, gently tap the housing toward the head, then try sliding the housing off the broken bolt. Repeat until it loosens up. I don't remember any threads being in the housing, probably got corrosion between the steel bolt and aluminum housing keeping the housing from sliding off. Hopefully the broken bit won't keep the housing from sliding off. Be patient and careful. The area of the head where the thermostat housing bolts thread into isn't that strong, and you don't want to marr it up, or worse, crack or break the threaded part of the head off, so don't be tempted to get the prybar out! When reassembling, I put anti-seize compound on the bolts to prevent this.



as they say, that's my .02, and good luck! (and be gentle!)

Ya know, sometimes the obvious just reaches out and smacks ya upside the head

I had it in my brain that there were threads through the housing. Don't ask me why, probably from the frustration of the broken bolt and my 3yo son "helping" me got in the way of rational thinking.

Agree with the patience and careful. I learned my lesson a long time ago about forcing things off of the block. There be no prybars used in this job.

I bought this XJ a couple years ago and now that I think about it, I never did replace the t-stat. Who knows how long it has been in there.

now it's time to go to sleep...haha