brake problem ??

[gilbo]

go to step on the brake sometimes doesnt wanna stop, pedal doesnt go all d way down at all, in fact feels like when u pump your brakes when the vehicle is not on. pedal gets really hard. any guess on what it might b, thks

[95Yukon]

there is a check valve where the vacuum line connects to the vacuum booster. If that is bad, it may not be retaining enough vacuum boost under some conditions to have good braking (just like if it were not running, like you mentioned)