hey guys on my 2003 hummer h2, i would say i had this problem for a while. so ill try to explain

for the first inch of brake pedal, there is no pedal at all tbh, like its just like a gap, its kinda annoying and i want to get that fixed but maybe thats normal
and then once i actually get real brake pedal, i get about 2-3 inches of real brake pedal action but then i notice when i push more i just get a air noise/hissing noise and maybe i am out of brakes?

the reason im bringing it up now is i was on the highway today and i guess it was windy so someone swerved into the other lane a few cars ahead of us, so we all pounded on our brakes like dominos.
gladly no one was hurt but thats where i noticed the air/hissing noise when i was pushing the brakes.

i dont know if this is normal for our trucks, my other vehicles have brake pedal all the way and dont have a hissing noise at the end or near the end


i recently got new brake pads, and did brake fluid flush with dot 3 with a new master cylinder, all bled etc. changed the master cyl cuz it was leaky

 

Nothing normal about that. Sounds like a bad accumulator in the hydro boost pump but it could be anything.

Check the entire brake system for leaks, fluid levels and pad thickness. If all are good you need to then look at master cylinder and hydro replacement/repairs.

Tim

 

did all of this start after getting the brakes serviced?

Have the braking system bled by a shop that can cycle the ABS pump with a scanner,

 

More experienced members on this forum can offer better advice, but definately not normal.

You changed your pads but what about the rotors, they could be worn or have uneven wear?

Mine performed and sounded similar until new pads and rotors on each corner were fitted, now it stops on a dime.

As legerwn mentioned, the Tech2 auto-bleed is very effective, the master cylinder needs to be manually bled 1st, but you've probably did that already.

You may find this thread interesting.

 

have someone press on the brake pedal and watch your master cylinder and listen to see if if the "air swoosh" sound is coming from it also watch the level of the fluid. if you see a lot of turmoil in the brake fluid then your master cylinder inner seals might be worn and gushing back the fluid pressure into the fluid reservoir instead of to your brake system.
if it was a hydro boost issue you would have a hard pedal, a bucking pedal, or even a fully applied stuck pedal.
worn out rotors and brakes may also contribute to excessive travel for obvious reasons.. the caliper pistons need to travel further then they should, that also allows rust to develop on your caliper piston slides which will in turn eventually lead to a stuck caliper or damaged seals allowing air and moister into your sealed brake system or your calipers to leak fluid onto your braking surfaces.
it was more pronounced on drum brake systems that used brake cylinders its the same for clutch slave cylinders as they function with the same concept.

 

thanks! yeah sorry i wanted to add that i had this problem before i got the brakes swapped as well but never thought much because i didnt ever use my brakes much. i used to have a more spongy pedal before
after i got the new pads put in, i noticed a way better firm pedal now but it still has that gap where i press the brake pedal but i dont actually hit real brake pedal until ive pushed it forward like an inch.
and the hissing/air noise when pushing the brakes all the way or near all the way has been a issue for a while i believe.

in normal day to day driving i dont notice anything wrong. the only annoyance i have is the excess brake pedal travel. i never have to use my brakes that hard where i would notice there was a problem until yesterday. i did get a new master cylinder when i got the new pads brake fluid in. the old one was leaky.
mecahnic said rotors were fine, he did the fingernail test, and said maybe my one caliper is coming to a end soon because when he would use the clamp, i think it would be very hard to push compared to the other caliper

as of right now the brakes are perfectly functional, i can easily stop in normal city driving and never have had a brake scare. like i had the mechanic drive it and he said everything is fine. he said the brake pedal travel is kinda excessive but he couldnt find a way to fix it and said prob gm. i dont think he bottomed out the brakes otherwise he would have noticed the hiss noise.
i feel like it must be some hydroboost problem because

 

did your mechanic check the depth of the old master cylinder bore hole to the new one? some have a 1 inch deeper hole for the push rod. which would give you 1 inch of blank travel. hopefully you still have the old master cylinder to compare with.