Brake warning and stabilitrax warning cut off. learned from mechanic that the master cylinder was bad. our mechanic sees this regularly and believes someone needs to review the severity of the problem. i have 78,000 miles on this vehicle but my son-in-law's gmc p/u has 38,000 miles and having the same problem. as i understand the seal breaks and fluid is draining into the boot. is there any concern at this time with the brake system completely failing due to the problems with these master cylinders? once again, our mechanic sees these failures regularly and believes gmc needs to address the issue.