Why is the brake very hard and difficult to press after the car is parked overnight?

[LeilaniMarie]

When the brake is very hard and difficult to press after the car is parked overnight, it is usually due to a problem with the vacuum booster pump in the vehicle's braking system. Insufficient vacuum pressure will prevent the vacuum booster pump from functioning properly. Methods to address air leakage in the vacuum booster pump: If the sealing ring of the vacuum booster pump is worn or lacks elasticity, it should be replaced promptly. If the connection port of the vacuum booster pump is loose or damaged, apply sealant and tighten the connection for loose ports, or replace the sealing components for damaged ports. If there is air leakage in the vacuum booster pump's piping, the leaking section should be replaced. Symptoms of a faulty brake vacuum booster pump include: unusual noises when pressing the brake, a very hard brake pedal, delayed return of the brake pedal after pressing (it may slowly return to its original position or, in severe cases, not return at all, as if stuck).