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Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 1686
Experience:  GM Grand Master Technician 2007. 14 year experience.
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GMC Sierra 2500 HD Classic SLT: I have a 2003 GMC sierra 2500

Customer Question

I have a 2003 GMC sierra 2500 hd diesel truck with 170K, one day on the way to work the rear brakes had locked up and started smoking, so I changed the brake pads, calipers, master cylinder, replaced the hydro boost 6 months ago because it was leaking, after all that I drove it then it locked up and smoked again, bled the brakes multiple times to get going again throughout this process and in between, so, then I changed the ABS module, brake lines and proportioning valve, everything is brand new, went to the auto parts store where they inserted their computer to find a code, and nothing came up, confused as to what should I do now?
Submitted: 2 years ago.
Category: GMC
Expert:  JFN1 replied 2 years ago.
Did you replace the rear rubber brake hose at the axle?
Customer: replied 2 years ago.
Yes, all the hoses have been replaced.
Expert:  JFN1 replied 2 years ago.
OK. When the caliper locks up, if you open the bleeder valve on the caliper, does the pressure release?
Customer: replied 2 years ago.
Haven't gotten a call yet. Back to typing. The answer to your question, is, Yes!
Expert:  JFN1 replied 2 years ago.
I'm sorry, I've been multitasking and not able to make a phone call out. If you do the same thing and relieve pressure at the master cylinder, do the rear brakes release?
Customer: replied 2 years ago.
How do you relieve pressure at the master cylinder? I've only released pressure at the rear caliper.
Expert:  JFN1 replied 2 years ago.
Just use a line wrench and loosen the lines, one at a time. The point here is to see if the pressure is being held in the hydraulic lines by the master cylinder, or by some component further down stream.
Customer: replied 2 years ago.
Okay, I will get back to you.
Expert:  JFN1 replied 2 years ago.
Customer: replied 2 years ago.
Sorry for the last response, loosened the lines at the master cylinder and that seemed to do the trick, so far, so good. Thanks so much for your expertise.
Customer: replied 2 years ago.
JFN, Apparently the truck isn't done with its issue, we bled the master cylinder, and everything was fine for a week, now the brakes are locking up again, what now?
Customer: replied 2 years ago.
Can you still help?