The truck is a 5 speed, 2WD extended cab with 165,000 miles on it. It had sat outside for a month or two without being driven, in December. When my brother started it up and put it into first gear, the back wheels spun on the wet grass but the front wheels wouldn't budge. Ditto when he tried backing up. He rocked the truck between 1st and Reverse a few times and whatever was sticking let go. Everything back to normal now.

Any ideas what could have caused that to happen?

 

Rotors would of rusted/seized to the pads.

 

Best way to free it up: (besides just dragging the truck forwards until they break free)
Pull the calipers and tap the pads off of the rotors with a hammer, inspect, re-install. Done.

 

Thanks.

I can certainly see a pad seized to the rotor causing the problem. But since the pads make contact with the rotor only when the brake pedal is pressed, how could the pad have come in contact with the rotor in the first place while sitting for a month?

 

There could be insufficient brake/brake booster pushrod free play.

 

Clearance is less than a sheet of paper. It's just rust build up. It can happen overnight to a minimal level that you may not even notice.

 

Well, it HAS been the wettest year in decades in KY and the truck has been outside all the time. The rust theory makes sense.

I never realized the clearance is that small. Which makes me wonder how the clearance gets set when the old pads are replaced by new, thicker pads. Looks like if the clearance is only a paper width, and I put new pads on, they would hit the rotors all the time. Do the calipers automatically adjust the clearance?

I assume the rust buildup is mainly on the rotors, not on the pads? And can be sanded off?

 

Basically, yes the calipers self adjust, this is why it's so important to grease the caliper slides when fitting new pads.

Depending on how bad the rust is, yes you can sand the rotors & pads.

 

When one goes to install new pads, the pistons are pressed back into the calipers and then there is plenty of room to install new pads, actually quite easy. There is a special tool for this (under $10) or one can use a large C-clamp; the old pads are used to press the pistons back because they are larger surface than the C-clamp or tool. See



I only replace rotors or drums if scored or out of round; the brake pad will clean up any rust from the rotor as you brake/drive. For the record: I use Wagner Thermo Quiet brake pads and brake shoes, buy through Rock Auto. Generally one will go through 2 sets of front brakes for each set of rear brakes.

 

Thanks Cusser and 'Reaper. That's good info.

I replaced pads on this Mazda in 2003 and now that you reminded me I did use a big C-clamp to push the pistons back in. I think I used AZ's DuraLast brand pads. Long time but it's a seldom-used vehicle so they only have about 10,000 miles on them. Lots of moisture from being outside all the time! Hopefully this lock-up was a one-time thing. I'll keep a hammer and a wooden peg in the truck just in case it happens again.