Air in the brake system can make your brake pedal feel spongy and vague. You should flush the fluid every two or three years, ...

have air brakes, and that sound is made by the safety valves resetting the air pressure after use. True air brakes are ...

But the action of pressing the brake pedal opens a poppet valve, allowing this second chamber to fill with air at atmospheric pressure. This pressure then forces the piston to move towards the ...