Need late model brake help

[Ralph LoGrasso]

I need some help with the brakes on my '96 Tahoe. I think the brake booster is on its way out (very soon), but I'm not 100% sure. The pedal has always been very mushy, and the truck is definitely underbraked. Recently, I noticed that when I depressed the brake, I hear a very loud woosh, a vacuum type sound. I thought at first that I had a vacuum leak, and that may still be it. The sound was always there, but not as loud. If I pump the brakes on my truck two times or so, the mushy pedal goes away. However, recently (the past two days), the pedals has been much more firm at times, too firm infact. When the brakes are pumped it becomes VERY difficult to depress the brake, the pedal gets that firm. Today in traffic, I was on and off the brakes, I came to a stop light and began to roll forward, when I tried to stop, I had to really push the pedal, and it only moved about 1" down, but the truck did stop. I had to hold some pressure on the pedal as well. When the light turned green, I let off the brake and stepped on the gas lightly, the truck felt as if it were in neutral, it began to roll forward, but very slowly, and then the brakes released I guess, and the truck started to move, after it slightly jumped forward.

What do you guys think is causing this?
Bad brake booster?
Pressure in the lines?
Vacuum leak?

It cannot be anything with the ABS, because it is disabled.



I'm going to go outside now and try to figure it out, but I need to get this fixed asap, as this is my only mode of transportation.

Thanks for the help,

[Q ship]

Ralph from what you described it sure sounds like the booster is shot, you now have manual brakes!

[Chevyman73]

You are right on it Ralph. The late model Chevrolet truck booster is almost a joke in the salvage industry because of the frequency they are replaced. Second runner up to that is a tie between the tail light circuit board and wiper module. They can be a pain to remove since they mount so close to the column mounting point at the firewall. Not really difficult, just time consuming. They are about $75 used and around $130 remanufactued.

[68BNUT]

I had an 80 Malibu that started doing that to me pedal would sink if you held it then act weird with you pumped it, It ended up being the Master cylinder I bought a rebuild kit and rebuilt it fixed my problem, Not to sure about the whooshing sound though??

[Ralph LoGrasso]

Thanks for the responses, guys. You guys are quick today! I'm going to start with the booster, because I'm almost positive that that's the problem. If that doesn't work, I'll try the master cylinder like Justin recommended. I'm also going to flush out the whole system, and replace the brake fluid.

Thanks again!

[Rick Dorion]

On my 97 GMC, when the pedal started getting rock hard at times, it was one of the abs sensors. In gneral, though, the brakes are terrible on those years. Keep us posted, Ralph.

[Ralph LoGrasso]

Rick, I experienced just that a few months back. The abs sensor on the passenger side (front) reads a different speed (much slower) than the other 3 sensors, so it tried to lock the brakes and stop the car. After this almost caused me to crash (thankfully it was 1 block from my house late at night) I disabled the ABS by pulling the fuse. I agree though, these trucks are definitely under-braked.