Size might be a trial and error kind of thing. A "set" of torx sockets is inexpensive at an auto parts store.
Mainly, I wanted to suggest removal and installation as not to ruin the tool or the screw.
I'm a Jeep CJ feller, pretty much the CJs were nothing but torx fasteners.
I'd like to have a heart to heart with the inventor of this crazy concept.
I've replaced all of mine with real bolts and chucked the crappy torx into the woods!
Bear with me, the first pic I show is a allen head, when I searched for a torx in my stuff, there were none!
This technique is going to be the same anyway.
Pic 1) Select the correct size
Pic 2) Install the tool into the torx fastener
Pic 3) Lock vise grip pliers firmly onto the tool (using a ratchet usually results in a broken tool or stripped out fastener (star)
Pic 4) I only have two hands. I needed three for this pic. One to snap the pic, one to hold the hammer, one to apply pressure to the vise grips (not shown here).
So pull on the vise grips, hard pressure, we are not trying to turn the tool (or the fastener)! Just giving it pressure.
Hold the vise grip pressure and whack the torx socket repeatedly with the hammer. Eventually you will learn how hard to smack it when the fastener will finally begin to turn.
You can install the fastener back using a ratchet and some "blue" removable "Lock-tite" on the threads.
Pic 5) Not a single torx left in my Jeep!
Let us know if this helps.
Images (Click to enlarge)
Wednesday, October 9th, 2019 AT 8:07 PM