There's a lot of confusion and conflicting information here. "Fails at times" is not the same thing as "goes down to the floor while in park but seems to recover somewhat as I drive and apply brakes". First of all, it has been a characteristic of GM vehicles since the mid 1970s for the pedal to be able to go to the floor while standing still, but if you were driving at hghway speed, the brakes would have been locked up long before it reached that position. There simply isn't much force required on the pedal to activate the brakes so pedal position can be misleading. Another way to say this is the brakes can be locked up like normal as you're sitting at a stop light, with the pedal only pressed half-way to the floor. At that point, the pedal can be pressed further. That is characteristic of GM systems.
Replacing rotors has nothing to do with the pedal position. Rear drum brakes out-of-adjustment can cause a low pedal but that isn't common for the sel-adjuster mechanism to give problems. Replacing "the whole brake system" is comparable to replacing the miles of electrical wiring because one tail light bulb is burned out. I suspect you will become accustomed to the characteristics of the brake pedal after driving this vehicle for a while. Replacing everything in the system will just put the same parts back on the truck so nothing will change. If you're thinking replacing everything would magically catch one defective part, that first of all implies there IS one defective part, and, the proper approach would be to have the problem diagnosed to identify that one part and replace just it, not everything.
The failure you're probably referring to has to do with total loss of braking due to a sudden failure of the anti-lock brake hydraulic assembly. This is an intermittent problem. When the problem doesn't occur, there is no defect present in the system, and nothing for the mechanic to find. The last one of these I read about involved the fellow's brake pedal going to the floor as though it wasn't connected to anything, and he sailed right through a red light. This happened to him about once per month.
If you have anti-lock brakes, give yourself enough stopping distance that if the pedal goes to the floor, you have time to release it and press on it again. In the rare event this happens on two pedal strokes in a row, be sure the parking brake is working properly. That will apply the two rear brakes. Stopping power will be greatly reduced, and stopping distance will be greatly increased, but at least you will be able to stop. This problem does not apply if you don't have anti-lock brakes.
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Tuesday, March 16th, 2021 AT 10:09 AM
