When I step on the brake pedal there is an imediate resistance almost as if there is no power. It releases and then the braking is delayed but the brakes still work. At a stop with my foot on the pedal there is a hissing sound under the dashboard as if it is releasing pressure. Could this be a sign that the Power Booster is about to go? What else could it be? I can't find any leaks anywhere.

 

my experience with leaking diaphragm in booster is that yes, it'll make hissing noise, but then pedal goes down to the floor slow but steady, with brakes still working a-ok.
in your case, as it catches right on, so i am assuming pedal stays up high, i'd start with being suspiscious of master cylinder. maybe check clearence underneath brake pedal, as silly as it sounds. i hadfloor maton my ranger so that created a ridge underneath the pedal.
if i am wrong on the pedal height, and pedal catches at regular height and slowly goes into the floor - probabaly booster diaphragm. you can replace it, you know. also, check the power booster air line. unless you have hydraulic assist,i know nothing of it.

 

Thanks Uk. After further review I believe that it is the Power Booster and that the failing booster is caused by the slight leak in the Master Cylinder. I am going to replace both since they are original equipment. I have located some re-man parts for $180 after core refunds.

By the way, it's a1996 Silverado w/ 160,000 miles. It's a lot cheaper to fix than to buy anothertruck. I canbuy a lot of $4/gal gas for $30K.

 

Does anyone have any advise on removing the brake pedal pin on the '96 K1500? The steering column is in the way. I tried disconnecting the steering column but it won'tbudge. Is there something that I am missing?

 

so it's master, not booster.
i'd leave booster alone, if you are sure it's not it. if you just have to replace it, make sure that pushpin in booster is properly set on height. if it's tooo low, you'll have poor brakes, if it's too much, brakes will drag. been there.
if i were you, i'd replace master first, even better - just overhaul it, it is CHEAPER even than buying used one. then give it a shot. hiss points towards leaking diphragm though.

 

I replaced both master and booster. Although, the master looked to be OK. With 12 years and 160K miles I think it was the right thing todo. Brakes work great now.

The tip of the day for the next person who tries this on this model: Take the lower part of the dash board off and the steel brackets below the steering wheel. Un-bolt the sterring column supports and pull the column out a little and kink the shaft downward to gain access to the keeper on the brake pedal pin. You will have a few inches clear to seethe pin and to get a hand and a pair of 90 degree needle nosed pliers up there. Remove the pin from the brake pedal, unbolt the four booster bolts, you are on your way. Much easier to re-install than to remove.

Hope this helps the next guy.