why do all the calipers lock up at the same time after driving over 2 hours the lines are good and all seem to lead to the booster not getting enough vaccum
brake on 1993 Volkswagen Jetta
first check that the pedal releases all the way. sometimes even a misadjusted brake light switch can hold the brakes applied. while you are experiencing the "lock-up" loosen the master cylinder bolts slightly with the engine off. if the brakes release then its a booster or pedal problem. check if there is rust in the booster indicating water ingress. if they still hold, the master or abs may be holding pressure. try loosening the fluid lines to release pressure at the master first. if it releases then the master is bad. this usually happens when the fluid is not relaced ever 2 years as required. if you loosen any lines, dont forget to bleed the brakes before you drive off.
Anonymous was me "some guy" i forgot to log in.