2002 Suburban: Poor brake performance - long-time problem

[MadFrog]

I have a 2002 Suburban with 115k miles that I bought used from a dealership several years ago. It has always had a soft brake pedal (I have driven other Subs of similar vintage that had a good brake pedal feel).

 

What I mean by soft brake pedal is twofold:

1- it feels soft, there is a lot of travel

2- test at 45 mph, on a dry road, with properly inflated tires and slam on the brakes. The pedal will go almost to the floor, the truck will slow down, but will not generate enough braking force to kick in the ABS brake system.

 

I have, over the course of my ownership:

- replace old worn pads with standard auto parts store pads on all 4 corners

- flushed fluid

- replaced all 4 rotors

 

no improvement. Dealership tells me it's because of the cheap pads I am using. Fine.

 

A year later, the cheap pads are not worn, but one my rotors has warped, causing shaking so I:

- replace all 4 rotors with AC Delco units

- replace 3 out of 4 calipers (seized bleeder screws, cheaper/easier to get reman'ed calipers)

- replace pads on all corners with Hawk LTS brake pads. (I know those are good quality pads having used them before on other applications where I towed heavy trailers.)

- flush brake fluid

- burnish pads according to Hawk instructions

 

Still a soft pedal, with no braking performance improvement.

 

The only variables left in the system are the brake lines, or the master cylinder. Externaly, the lines appear to be fine.

 

Is there a test I can perform on the MC to determine if it's good or not? My experience has been that a bad MC will typically be ok until you come to a stop where the pedal slowly sinks to the floor. I am NOT experiencing that symptom.

 

Should I just throw parts at it and replace the MC and lines anyway?

 

Thanks in advance for any suggestions.

[desrtrat]

if your not leaking break fluid from your lines i would not replace them..but i would start by replacing your rubber break lines with braided stainless. over time the rubber will soften up and expand when the breaks are applied. it may not totally cure your issues, but will help out alot. another thing is replacing the vac. booster and master cylinder and installing a system from a 2500/3500