Hello Lunarboy,
When you remove the vacuum line from the booster and then depress the brake pedal, it feels very hard as there is now no pressure differential across the vacuum chamber,..ie both sides are at atmospheric pressure.
It is not a requirement for a hard brake pedal that there be a leak from the slave cylinder allowing brake fluid to enter the vacuum chamber, but there usually will be, especially in a unit that has seen some years of service.
The air control piston is the item which if stuck within its bore will prevent a vacuum from being formed on one side of the chamber, thus no pressure differential and no vacuum assist.
Ten years or 100,000 miles is typically the most you will ever get out of a booster.
Ron.
When you remove the vacuum line from the booster and then depress the brake pedal, it feels very hard as there is now no pressure differential across the vacuum chamber,..ie both sides are at atmospheric pressure.
It is not a requirement for a hard brake pedal that there be a leak from the slave cylinder allowing brake fluid to enter the vacuum chamber, but there usually will be, especially in a unit that has seen some years of service.
The air control piston is the item which if stuck within its bore will prevent a vacuum from being formed on one side of the chamber, thus no pressure differential and no vacuum assist.
Ten years or 100,000 miles is typically the most you will ever get out of a booster.
Ron.