Why does the brake fail after a manual transmission car stalls?
3 Answers
Car stalls after the brake can not be stepped on the reason is that the brake booster does not work after the engine stalls. The following is the related content: For naturally aspirated engines: The vacuum that forms the boost comes from the throttling effect of the intake manifold throttle. For turbocharged engines: The vacuum comes from the vacuum pump. Therefore, the vacuum can only be generated when the engine is running. After the engine stalls, the vacuum source is no longer continuous, and it is impossible to provide boost. Boost: It is the force that helps people control the car. For example, power steering helps to turn the steering wheel easily; brake booster: A light step can produce a large braking force on the car. Without these boosts, it would be very difficult for people to operate, making it hard to turn the steering wheel or step on the brake. The working principle of the brake booster This is a vacuum booster, which helps to step on the brake. Working principle Pressure difference: When the brake pedal is stepped on, this force is transmitted through the booster push rod on the right side of the booster. After a series of changes, the two chambers separated by the diaphragm, the left chamber will have a certain degree of vacuum, and the right chamber will be connected to the atmosphere, forming a pressure difference. The pressure difference forms a leftward force on the central push rod, which is the brake boost.
I've been driving manual transmission cars for many years, and brake failure after stalling is quite common. The main reason is that once the engine stalls, the vacuum booster loses its power source, making the brake pedal very hard to press. You have to stomp on it hard to stop the car, which feels like a brake failure. Actually, it's not a real failure—just the loss of power assistance. Once, I stalled on a steep slope and almost crashed, so I immediately pulled the handbrake in panic. During regular maintenance, check the vacuum hose for leaks or aging, and change the brake fluid periodically. Now, I always remind my friends to test the brake pedal's softness by turning the key to the ON position before driving, just in case. Safety first—never expect the brakes to work easily when the engine stalls.
I just got my driver's license not long ago and drove my first manual transmission car. I experienced a situation where the brakes failed after stalling. That day at the intersection, the car stalled, and the brake pedal suddenly became as hard as a block of iron and couldn't be pressed. Fortunately, the speed was slow, and nothing happened. Later, a car-savvy friend told me that this is because the vacuum booster requires the engine to provide vacuum, and once the engine stalls, the assistance is lost. This is not a malfunction but a design issue. If you encounter a similar situation, don't panic—step on the brake hard or use the handbrake to stop the car immediately. Now, every time I get in the car, I start the engine and test the brake feel first. Developing this habit can avoid a lot of trouble. New drivers especially need to be aware that stalling on a slope poses significant risks.
