The power assist produced by a vacuum-operated brake booster depends on which factors?

Prepare for the Automotive Service Technician Period 1 exam. Study with flashcards and multiple choice questions, each question has hints and explanations. Get ready for your exam!

Power assist from a vacuum brake booster comes from the pressure difference across the diaphragm, times the diaphragm’s effective area. The force applied to the master cylinder equals the pressure differential between the vacuum on one side and the atmospheric (or intake) pressure on the other, multiplied by how large the diaphragm is. A bigger diaphragm gives more surface area to convert the same pressure difference into force, and a larger pressure difference (more vacuum or lower opposing pressure) increases the force available for assist. The vacuum source is the engine’s intake manifold, so the amount of boost can vary with engine speed and load. The other choices don’t affect this mechanism: brake fluid color, engine horsepower, and driver weight do not change the diaphragm area or the pressure differential that provides boost.