'10 2500HD - spongy brakes, slow pedal return, "hiss" when brakes fully depressed

[calcheyup]

As the title states - have a '10 2500HD that has had what I would characterize as a "spongy" brake for...well, for quite awhile. I took it to the dealer and they flushed the brake system and bled everything, returned the truck saying "all okay," the pedal feels the same to me. Anyway, I didn't feel like wasting any more money if that's the sum of their efforts. The truck itself actually seems to stop fine. I don't feel at all like actual brake action is an issue. However, the pedal has always felt a little soft to me, it is slow to return, and when I put the pedal to the floor, the truck drops it's idle slightly and I can hear what I would call a "hiss" coming from seemingly around the region of the pedal.

 

Brake fluid and PS fluid are full, and have never had issues leaking either of them. No fault codes displayed. Only other sort of random thing is I've had to replace the brake switch probably 4 times in the life of the truck (I've had it about 8 years). The brake lights will stay on after applying the brake, and I'm curious if the slow return has anything to do with that or if it's just another, random problem.

 

Internet searching has led me to believe taking a shot at replacing the Hydroboost might be worthwhile. Are these symptoms consistent with a Hydroboost on it's way out? Anything else that's more likely?

 

Thanks.

[richard wysong]

do you have hydro-boost or vacuum booster?

[calcheyup]

It’s a HB, Line running off it to the PS reservoir. Was HB not standard on the ‘10 3/4 ton?