How does a 2003 Chevrolet Truck vacuum pump brake booster turn on & off? What controls it?

Silverado 1500 5.3 engineHow does a 2003 Chevrolet Truck vacuum pump brake booster turn on %26amp; off? What controls it?
A brake vacuum booster is just a large diameter diaphragm that has one side connected to an engine vacuum source (a port in the intake manifold, usually), and the other side connected to the brake pedal linkage. It acts to boost brake pedal effort by converting the low differential pressure of engine vacuum to higher pedal force by means of the leverage it adds to the mechanical brake pedal linkage.





So, when the engine is running, vacuum is available, and the booster makes it easier to apply the brakes with low pedal effort. Once the engine shuts off, the brake booster may have enough stored vacuum for one or two assisted operations of the brake pedal, but soon thereafter, loses its ability to assist in the application of the brakes, and the brake pedal requires noticeably more effort to achieve the same amount of braking force on the vehicle.





Vacuum boosters look like big metal mushroom tops, about 10 inches in diameter, and are usually mounted up near the firewall on the driver's side, directly above the brake pedal linkage.How does a 2003 Chevrolet Truck vacuum pump brake booster turn on %26amp; off? What controls it?
hey there may be a real tech here Chris W is very correct good job the rest of you are also correct but things are getting a little more complex guys ya gotta try to keep up





again listen to Chris this at the point of time in which we live is sometimes better left to those of us who are trained good luck
The previous answer describes very well how a typical system works. But your vehicle has a supplimental brake assist, basically an electric vacuum pump that will assist the vacuum supplied by the engine if it falls below about 7in hg. What turns it on is the computer, but there is a built in pressure sensor in the pump that determines if vacuum is low. If you see a message ';reduced brake power'; , or ';Service brake booster'; you should have someone with specific knowledge of this system pinpoint the problem. Good luck.
Once you depress your brake pedal the push rod going to the vacuum assist activates it (with the engine running).The valving of the vacuum assist allow the engine vacuum to help push in turn the piston of the brake master cylinder. In this manner, the vacuum assist makes braking an easy task instead of making you push really hard to make the master cylinder do its job.