What are the symptoms of a faulty engine vacuum pump?

[DelJameson]

When a car's vacuum pump fails, the symptoms may include poor braking performance or complete loss of braking effectiveness; visible oil leakage at the external connections of the vacuum pump; and slow or non-returning brake pedal. Vacuum Booster Pump: The function of the vacuum booster pump is to use the vacuum generated during engine operation to provide assistance to the driver when braking, making the brake pedal easier to press. If the vacuum booster pump is damaged, this assistance is lost, making the brake pedal harder to press. Generally, the vacuum pump cannot be repaired and must be replaced. Its internal structure consists of a piston (with an O-ring seal) and a cylinder. The working principle relies on the vacuum from the engine intake to assist in braking. It does not require special lubrication. Brake Booster Pump: The brake booster pump is a large-diameter vacuum chamber with a diaphragm (or piston) in the middle that contains a push rod, dividing the chamber into two parts. One part is connected to the atmosphere, and the other is connected to the engine intake manifold via a pipe. Therefore, when the engine is off, there is no intake vacuum, and thus no assistance, requiring significantly more human effort for braking.