Do I need a new master cylinder???

[chessy56]

As I approach 300K miles on the LB7, I noticed that even after a complete brake job, I just don't seem to be able to maintain a good stiff feel on the brake pedal. Anyone ever have to replace their master cylinder on a '01 2500HD? I'm wondering if it's time for a replacement? Anyone?

[DmaxMaverick]

Many things can cause a "soft" brake pedal. If it isn't leaking down (bleeding off while standing on the brakes for a long period), then the MC is probably OK. The leading cause of soft pedal is air in the lines and/or calipers. Others include worn out soft lines (hoses, they can get "spongy"), broken/cracked brackets, or sloppy/worn adjusters.