This is a stubborn bolt issue on '66 F250. The lower alternator mounting bolt won't loosen. I've tried 17" 1/2"-drive breaker bar, and my air wrench. No go. There's plenty of room to operate; battery & radiator are out, grille's off. Help.

 

You have a seized bolt due to metal mismatch - steel into aluminum.

Spray the bolt with PB Blaster and let it sit. Also, you can remove the alternator bracket from the engine and work on the thing out of the truck.

 

Maybe I'm missing something in all the grease under there, but looks to me like the lower alternator bolt goes right into the engine block, from which it will not budge. The bolt (5/8" head) passes thru the alternator housing, then thru what appears to be an aluminum spacer, then directly into an ear of the engine block. There's really no bracket involved at this lower bolt point. There's a bracket for the alternator top bolt, but that's not the problem area.

 

Get the engine good and hot by running it and use a rocking motion back and forth (low on the forward) to loosen the bolt if it is seized in the block. Do not "hammer" on the bolt head in either direction for a long period of time. Once you have some movement, squirt WD-40 or something between the block and bracket and hope it soaks in.

Touch the bolt, if it or the impact socket starts to get hot, stop for a while. Do not get tempted to just crank down on the bolt with a bigger bar. All you will do is stress/yield the head and it will break inside the block.

This method is used for water pump bolts, but, works for just about anything.

 

This method sounds good. Wish I didn't have to wait 'til radiator, etc., are reinstalled to warm it up and try. I can easily resist the temptation of a little propane torch on the bolt head, but I wonder if a heat lamp or even a 100w bulb under the bolt site would get the temp up to get the same effect as a warmed-up engine? Thanks for the good-sense help.

 

Exactly!

I recently watched that rocking motion in action. After decades of breaking off bolts myself by wrenching too hard, I watched a true master at work. I think he soaked the threads with Kroil (or Aero-Kroil -- someting like that), and the proceeded to slowly rock the threads back and forth. I thought "this is soo boring" and "that plug will never move," but they did. My eyes probably popped out of my head when the things started to turn on its own. I would have been tempted to wrench it hard the rest of the way. But the master rocked it back and forth all the way out. I watched him do this several times with rusty, seemengly "permanent" allen-head pipe plugs for the water and oil passages in my own block.

Good luck. Be patient. And you'll get it.

 

The frozen bolt situation has developed further. Turns out the bolt is not frozen in the engine block; it's bound up in the alternator housing. This lower mounting bolt runs first thru the 1/8" thick steel bracket, then thru 3" of aluminum alternator housing, then thru 1 1/2" of spacer, then into the block. By releasing the alternator upper mounting bolt, I get a bigger arc turning the lower bolt. This lower bolt then moves freely in the block, but the alternator itself moves right with the bolt rotation, and rotation is stopped when the alternator hits the inner fender apron. The spacer spins freely. So, the notion that it's a steel vs. aluminum bind is probably correct. I applied a little heat, first with a light bulb for awhile, then got a little serious with a propane torch. Added some Power Blaster to this process. So far, nothing. A plumber came by to bid some work for me and opined that it would require a fair amount of heat. If I grind off the bolt head, the alternator housing still won't clear the bracket without some drastic bending. Surely the aluminum alternator housing cannot be threaded for the bolt? It's crazy that the hole thru the housing is so small as to result in a bind-up with the bolt. Any more ideas for separating this unholy couple without a grinder?