My mother drives a 1994 Cavalier, there are 153000 km. On her car. The problem she's having is occasional loss of break pedal. We've checked the wheel cylinders for leaks as she's topped up the fluid every week and a half. The master cylinder doesn't show any leakage. It is only the odd time that the peddal goes to the floor and is fine again after that for another little while. Any idea what the problem could be? I'm baffled, I always thought that ment the master cylinder needed to be replaced.
Thank you for your help.