Ok, I can go with that. (It’s a bit of a relief!)
In this case, the Explorer has under 75,000 miles on it & was garage kept all but last year. But I will check for any signs of corrosion or sticking of moving parts, of course.
The Toyota has over 148,000 miles on it, is 13 years old, has been kept outside all its life, and it appears the guys who put in the last pads did not do anything beyond putting in new pads, so a problem with a caliper there is less, uh, unsettling.
I really think this (Explorer) bolt problem is my lack of an air wrench, the oddly shallow bolt heads, and either some corrosion / no anti-seize in the threads or someone torqued in the bolts too enthusiastically, last time around.
Maybe it’s “all of the above”. (”All of the above” seems to happen a lot.)
Thanks again!
Ok, I was delayed again by rain, but, we were able to get the caliper bolts off, today.
I picked up an air wrench, but, it also failed to get the bolts loose. I was stunned. Possibly my compressor does not have enough air flow, but, I tried multiple short bursts, with the idea that surely the tank could supply enough air for two second long bursts. Air pressure @ the tank is plenty adequate, and the engaged surfaces of the bolt heads “shinied up” quickly / nicely from the impacts, but, no luck on turning the bolts.
The solution was to grind off the bevel on the 17mm socket, use a longer (25”) breaker bar, making sure the bar stayed @ 90 deg. to the swivel head (one HAS to turn the front wheel for enough clearance). Then I hung on, as tight as I could, to the swivel head and socket, to keep it “square” on the hex head while putting “some” torque on the bar, and my wife gave it all she had @ the handle of the breaker bar.
THAT did it.
The bolt threads look clean, with no sign of thread-lock or corrosion.
Obviously these bolts are in a spot where they CANNOT come loose in use. But, that said, I would estimate breaking free the tightest required ~180 ft-lb. of torque (95 lb. wife, ~22” out, pushing down, plus maybe 20-30 ft-lb. I could contribute from my position.) These bolts measure (at the smooth part of the shaft) 0.390” dia., very close to a 3/8” bolt. A table I checked says that a 3/8” Grade 8 bolt is good for 232 lb-ft. max. Dang...
The bolt is a 17mm washer head bolt, with the height of the head only 4.5mm (above the washer portion.) The shallow bolt head height really was the biggest part of the problem, as it made it tough for me to get enough torque applied.
BTW, I found some rather scary information pointing against the use of anti-seize on these bolt threads — will relocate and post...