2005 Front Caliper bolts

[smalltownusa]

Purchased new rotors and pads for my 2005 Ford Explorer Sport Trac.
This evening I started on the fronts. The top caliper mounting bolt 14mm loosened easy enough, but the bottom bolt has other ideas.
I'm not sure of the correct size. I'm thinking it should be 13mm, but with all the rust I am having a hell of a time.
I've stopped for the evening, but did hit it with PB Blaster. A 9/16" will not fit. I've tried 6 sided. The 13mm socket doesn't want to seat all the way although the bolt head looks clean with a mirror. When I try to wrench on it my wrench just pops off.

Haven't tried any heat yet, but may try some with a small hand held propane cylinder tomorrow.

P.S. I haven't depressed the pistons yet I was waiting to get these bolts a little loose.

 

[smalltownusa]

Today after further jacking up the vehicle I turned the wheel, and was able to pound on a 13mm impact socket on most of the way.
Surprisingly me (someone who is not the best mechanic) after selecting the lowest speed on my impact wrench the bolt backed right out.
So it's back to the project for me ! And afterward a new bolt.