Why Can't the Brake Be Pressed After the Car Stalls?
1 Answers
After the car stalls, the brake cannot be pressed because the engine stops working, no longer generating vacuum, and the brake assist disappears, making the brake pedal very hard to press. It is normal for the brake to be unpressable after stalling, as this is the design for almost all passenger cars. The brake booster relies on the vacuum generated when the engine is running to provide assist. When the engine stalls, the vacuum is lost. The booster's stored vacuum depletes with use, naturally making the pedal harder to press. For naturally aspirated engines, the vacuum for assist comes from the throttle's restriction in the intake manifold. For turbocharged engines, the vacuum is provided by a vacuum pump. Therefore, vacuum is only generated when the engine is running. After stalling, the vacuum source is no longer continuous, making it impossible to provide assist. For manual transmission cars, never shift to neutral after stalling while driving. Maintain the original gear and apply the brakes. Keeping the gear engaged allows the engine to provide some engine braking, helping the car stop faster. Methods for smooth braking include: gently pressing the brake pedal when decelerating; avoiding tailgating and developing the habit of braking early; using a lower gear on long downhill slopes to utilize engine resistance for deceleration; braking and slowing down before entering a curve, coasting into the curve, and accelerating out of it; and using intermittent braking (pump braking) on rainy days or gravel roads to improve driving safety.
