Here's a problem that's needing some input! Sorry for the long post.
Drove a lot (2k miles) and put it up wet. Drove a little and had some brake sticking that I thought was a stuck caliper, and it smoothed out pretty quickly. Drove to an airport and left town for a couple weeks. Coming home after 20 min or so of driving...clear load on engine and I suspected a stuck brake again. Pulled over, backed up, went forward, smelled hot, waited a while, went further, stopped and suddenly it was ok so I limped on home another 45 miles. Next few days it was either ok or locked up. It would sometimes unlock when I smacked the peddle. It seemed worse soon after starting. Finally gave up and dropped it at the LFD in the afternoon...figuring it was a bad caliper.
By noon the next day -- no word, and I learned they were stumped, so I stopped by. The mechanic had experienced the lock-up several times and has determined it is ALL 4 wheels locked up tight. This is what he did: 1) cracked a bleeder on right front and it unlocked. Drove it some til it locked, ran it into shop, lifted all tires off the ground, and cracked loose the master cylinder. As soon as it moved off the firewall there was a "bang" and they unlocked. He was going to next see if it was at the ABS/controller (not sure what it's called) that but then it wouldn't lock up anymore; I drove it for over an hour and couldn't get it to lock either. We decided to see if cooling down and testing again first thing in the a.m. will get it to lock. Other items he noted: all pads worn down about the same (not to steel--yet!), my drilled/slotted rotors are still ok, and we can't tell if the ABS is working since it's so dry. He has been working on superduties since the 1990s and never saw this on these rigs...
He's thinking it's either the master cylinder or the ABS/control unit - which is buried under my AFE filter and battery. But he's not wanting to just replace the MC (cheapest) without better diagnosis and I sure agree -- but cannot imagine how many hours of him driving around to replicated the problem that I can afford. I don't want to drive it far from the shop cuz i don't want to damage the rotors etc. So I'm sorta stumped!
Any thoughts? I'm thinking that with as many miles as I have maybe it's the MC piston getting stuck and not releasing. New front calipers and pads last November. Driven mostly regularly, fluid is clean, no other serious problems I can see...
Drove a lot (2k miles) and put it up wet. Drove a little and had some brake sticking that I thought was a stuck caliper, and it smoothed out pretty quickly. Drove to an airport and left town for a couple weeks. Coming home after 20 min or so of driving...clear load on engine and I suspected a stuck brake again. Pulled over, backed up, went forward, smelled hot, waited a while, went further, stopped and suddenly it was ok so I limped on home another 45 miles. Next few days it was either ok or locked up. It would sometimes unlock when I smacked the peddle. It seemed worse soon after starting. Finally gave up and dropped it at the LFD in the afternoon...figuring it was a bad caliper.
By noon the next day -- no word, and I learned they were stumped, so I stopped by. The mechanic had experienced the lock-up several times and has determined it is ALL 4 wheels locked up tight. This is what he did: 1) cracked a bleeder on right front and it unlocked. Drove it some til it locked, ran it into shop, lifted all tires off the ground, and cracked loose the master cylinder. As soon as it moved off the firewall there was a "bang" and they unlocked. He was going to next see if it was at the ABS/controller (not sure what it's called) that but then it wouldn't lock up anymore; I drove it for over an hour and couldn't get it to lock either. We decided to see if cooling down and testing again first thing in the a.m. will get it to lock. Other items he noted: all pads worn down about the same (not to steel--yet!), my drilled/slotted rotors are still ok, and we can't tell if the ABS is working since it's so dry. He has been working on superduties since the 1990s and never saw this on these rigs...
He's thinking it's either the master cylinder or the ABS/control unit - which is buried under my AFE filter and battery. But he's not wanting to just replace the MC (cheapest) without better diagnosis and I sure agree -- but cannot imagine how many hours of him driving around to replicated the problem that I can afford. I don't want to drive it far from the shop cuz i don't want to damage the rotors etc. So I'm sorta stumped!
Any thoughts? I'm thinking that with as many miles as I have maybe it's the MC piston getting stuck and not releasing. New front calipers and pads last November. Driven mostly regularly, fluid is clean, no other serious problems I can see...