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My dad has an '82 diesel that the front calipers keep sticking on. It doesn't happen every time he drives it but both sides do it from time to time. His mechanic has given up on it and basically my dad's decided to block off the front brakes and just use it on the farm. I hate to see him do that as he put a fair amount of money into it to get in on the road with these high gas prices. The calipers have been replaced and a new master cylinder was installed. All lines were flushed out and the proportional valve was cleaned. It has new lines on the front. I can't figure out what would be causing it unless it is the proportional valve and apparently his mechanic can't find a replacement. Any ideas?

I'd guess this has been looked at, but make sure the pins the caliper slides on are clean and greased a bit. Honestly, to me it sounds like typical caliper piston binding you get when they sit for a long time. The 83 Isuzu PUP I had used to do it all the time, until I tore apart the calipers and cleaned the piston and bore. It seems unlikely, but maybe the replacement calipers are just a crappy rebuild.

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95 Isuzu Trooper Daily Driver
86 Isuzu Trooper reliable backup
77 LUV 2wd stock beltway blaster (resting)
79 4x4 LUV project: 2.6L, 5spd, 31s (eventually)

MEPR: Man, my 4x4 makes all other LUVs look good

My truck did the same thing, squeeked like hell, and it was the calipers not retracting all the way. Took em apart, beet the caliper back with a hammer because they were froze to a point where they wouldnt go back all the way without some hammering. Once I got them to go back, I have not had any issues. GOOD LUCK, but I think 800xl might be on to something, when he says the rebuilt calipers could be bad also

It started on the right side and when it did it after replacing the caliper the mechanic took it back and put another one on there so it's doubtful there were 3 bad ones. Everything else has been replaced except the proportional valve and brake booster. It's got me stumped and his mechanic has given up. The guys been working on cars for 30 years. That's the scary part.

All of my troubles in that area have ended up being the caliper piston sticking in the bore. There is a lip of steel in the bore that is just outside the caliper seal but under the boot and when it sits the little bit of brake fluid that normally gets past the seal makes it rust to the point of tightening down on the piston. In all of my cases like this, pulling the piston out of the caliper and cleaning up that lip on the caliper has cured it, but I fought with everything else a whole lot before digging that far into the caliper.

That said, two replacements not solving the problem does seem a bit strange unless it sat for quite a while unused both (all three?) times. The only other source of binding I can think of is the caliper bracket. On 81+ the caliper slides on a pin and a bolt, and if something were wrong with the pin it could cause it to bind. Once they bind up for any reason and get hot they boil the brake fluid and just grab harder and harder. The pressure from boiling can even transfer to the other side and make it grab hard too.

So, you could look at finding another caliper bracket in addition to the proportioning valve.

_________________
95 Isuzu Trooper Daily Driver
86 Isuzu Trooper reliable backup
77 LUV 2wd stock beltway blaster (resting)
79 4x4 LUV project: 2.6L, 5spd, 31s (eventually)

MEPR: Man, my 4x4 makes all other LUVs look good