Repairing a brake booster on a 1997 chevy s10

The vacuum lines on a 1987 Chevy S10 Blazer are responsible for routing vacuum to various components such as the brake booster, EGR valve, and other systems.
A vacuum line diagram for your specific make and model of Chevy S10 Blazer can be found in the vehicle's service manual or in some cases, it can be found under the hood on a decal or sticker.
If the vacuum lines are loose, cracked, or damaged, it can cause various issues such as rough idle, stalling, poor performance, or even a failed emissions test.
It's best to consult the service manual, a professional mechanic or the dealer for proper diagnosis and repair of vacuum lines issues. These lines are crucial for the proper operation of many systems in the vehicle, so it's important to fix them as soon as possible if they are found to be damaged.

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I assume that you have disc brakes. These require a piston/s to push against the pads to tighten them onto the discs. 2 reasons they may not be working are the calliper pistons are seized up in the callipers and 2 the brake booster is not providing the power assist to actuate the callipers. If you have vacuum booster I would repair/replace the booster or check for vacuum at the booster hose. If you have electric pump booster then check that the pump is getting power and is working.

I can't remember what book says but I can't imagine it taking more than 3 or 4 hours taking your time even if you mess up and spill the fluid out of the Master cylinder and have to bleed the system. BTW, it's "Brake" Booster and sits on the firewall between the brake pedal linkage and the master cylinder. Oh and there are big differences between a 96 GMC Sierra and a Chevy S10 but the job is about the same and should take about the same length of time

Sounds like the seal on the brake booster is leaking. Replace booster.

CHECK THE GROUND CABLE ON DRIVER SIDE UNDER THE HOOD TO THE RIGHT ABOVE THE MASTER CYLINDER IF ITS BROKEN FAN WILL NOT WORK, RIGHT ABOVE THE BRAKE BOOSTER ITS SCREWED INTO THE FIREWALL. HOPE THIS HELPS YOU.

Check for fluid leaks and your brakes. If you see no leaks and your brakes are in good shape replace the brake master cylinder and bleed the system. The air you hear is because the pedal went to the floor. If the booster goes bad the pedal will get so hard you can hardly push it at all. I think you will find if this happened suddenly either you have a major leak or the master cylinder went bad.

bleed the abs unit first then bleed all the brakes

Try checking the headlight switch it may have broken contacts in it. Easy fix go to a salvage yard find same make and model truck, swap headlight switches.