T-Stat bolt size

[LEB Ben]

Alright fellas, as most of you know, I have a busted bolt that bolts down the thermostat housing. The shop couldn't get it done...and I know why, they had DULL, right hand rotation drill bits...so I didn't even bother using their stuff. So it's pushed out back in their parking lot for the time being. So my dad is sending up some fresh carbide left hand rotation drill bits.


My question is (Dennis this is right up your alley):


What is the size/dimensions of the tstat bolt? IE...diameter, coarse/fine thread, overall length? The head of the bolt is a 1/2"...I'm thinking the shaft is no more than 3/8"

I need to know so my dad send up the proper sized drill bits and the proper size tap. Vehicle specs...79 Bronco 351M. So even if you guys don't know off hand...maybe someone can take measurements for me? Thanks for any and all help in advance.

 

[Bricks]

5/16 dia, 18 threads per inch

Tap drill for that is an "F" .257 diameter

Drill a smaller (1/8 or so) pilot hole first.

Make sure you get it dead-nuts centered.


You could try to get it out using a l/h thread #10/32 tap (#21 drill) so you won't botch up the threads - then use the full size if that does not do it.

 

[LEB Ben]

Alright Steve...thanks. Got a question though...How the hell did you know what size that bolt was? I thought you were into newer steel? Didn't know you had dentside info filed away in that head of yours. Tried repping you, but I gotta spread the love.

 

[Bricks]

I've had a truck or two in my lifetime.

 

[LEB Ben]

I've had a truck or two in my lifetime.

HAHAHA...I hear ya...I was just impressed because that wouldn't be a tidbit of info that would stick in my head at least. Thanks again.

 

[Mil1ion]

i'm here now.................what steve said

 

[LEB Ben]

i'm here now.................what steve said

HAHA...ok thanks...dually noted.

 

[Mil1ion]

don't forget to melt some wax first down those threads first

 

[LEB Ben]

don't forget to melt some wax first down those threads first

OK? Can't say that I know what for...can you expound?

 

[Mil1ion]

Melted paraffin wax down into the threads acts as a lubricant

 

[Bricks]

If I were you Ben, I'd do everything I could to try getting that thing out before drilling the hole out full size. It's very, very difficult to spot that thing dead center and drill the hole straight and it's real easy to bust a tap. If you have to go full size go SLOW and be certain to clear the tap often (back it up a bit to break off the "chip"). Try to get a bottoming or "plug" tap so it will thread to the bottom of the hole.

 

[LEB Ben]

Yeah Steve...I hear ya...I'm definitely going to try, I just figured the taps would be good to have just in case, so I don't have to wait any longer and/or go buy the appropriate size.