Hi the reasons are simple the brake fluid is hyroscopic which means it absorbs water the water boils under severe braking. this can cause the brakes to sieze on. so change of fluid in older cars and trucks is advised. then we have the issue of air in the system air can be compressed to that is what makes the brake pedal spongy. yet again a change of brake fluid and bleeding the brake system is what is needed.

You have air in the system if you have antilock brakes it the truck must have the brakes bled using a scan tool

air. anytime a brake line is opened whether its busted or unscrewed air is able to get into the system. bleed the brakes and you should be fine

master could be shot. you also put a lot of stress on the brake system by running those useless tires and lifts. so the lines could also be shot as well..

Hello, I have a lifted 97 Chevy k1500 with a 350 on 37" tires and 9" of lift. I have had a brake problem since I bought the truck. Well kind of, I was romping on the brakes really hard one day and my front right disc brake busted a nut and it started to leak from where the brake line attaches to the caliper. Just cleaned the seal and tightened the nut back down and it was fine. Ever since that day my brakes are supper spongy and I have to push them all the way to the floor to stop, even after bleeding the lines starting with LR, RR, LF, RF they are still soft, seems like they were a little bit hard from when I bleed them about a week ago but now they are soft again. Is this a sign of master cylinder failure or would it be something else?