Please read before you post anything else......

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Since most cars today have disc brakes, at least on the front wheels, they need power brakes. Without this device, excessive power on the brake pedal would be required. The central part in the power brake system is the brake booster. The brake booster uses vacuum from the engine to multiply the force that the brake pedal applies to the master cylinder..........Because diesel engines don't produce a vacuum, diesel-powered vehicles must use a separate vacuum pump.

Do you understand now?