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Discussion Starter #1
Okay, this truck is the old body style like the 06. It came in with a leaking master cylinder. Along with the leak customer complained about a roaring right before it stopped. We changed the master cylinder and bleed the system with the computer and manual bleeding procedure. Got good pedal. So went for a test drive. about a mile into the test drive I noticed that sure enough when you slowed down right before the vehicle came to a complete stop it would activate the ABS. So, I speed up and just let it coast to a stop and I notice the brakes were starting to lock up. I turned around and headed home. When we got here both calipers on the front were smoking hot. Vehicle has no codes. The only abnormal thing on the computer was when the ABS activated right before stopping each time the right front dump valve was activating. Anyone have any issues like this on these trucks before?
 

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Very very common problem on these trucks. Usually as long as the wheel bearings are tight it ends up being the abs module. Not to say that is the problem though, it could be an issue with the harness going to the sensor or the sensor on the hub itself. When I worked in aftermarket parts I sold the modules fairly often for these trucks. I now work at a GM dealer and these are still parts we sell now and again. Make sure the front bearings are tight and go from there. Check the wires good too, you may need to do a resistance check to narrow down the problem.
 

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Discussion Starter #3
Very very common problem on these trucks. Usually as long as the wheel bearings are tight it ends up being the abs module. Not to say that is the problem though, it could be an issue with the harness going to the sensor or the sensor on the hub itself. When I worked in aftermarket parts I sold the modules fairly often for these trucks. I now work at a GM dealer and these are still parts we sell now and again. Make sure the front bearings are tight and go from there. Check the wires good too, you may need to do a resistance check to narrow down the problem.
Thanks for the info.
 

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You might try pulling the main ABS fuse to deactivate it and drive it some, then see if your calipers are still getting too hot.
 

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Discussion Starter #5
I did that. The issue is in the brake rod in the booster. I drove it again and once they started to lock up, I loosened the hold down bolt on the master cylinder and they released. As the fluid get warm and expands it can not return to the master cylinder because the rod is always pushing on the back just a little.
 
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