Power Brake Unit Does Not Boost
- Test For Power Unit Operation - Stop engine and apply pedal pressure several times to remove all vacuum from system. Hold pressure on pedal and start engine. Pedal will move slightly forward when cylinder is operating.
- Power Unit Does Not Operate - Vacuum check valve stuck closed. Vacuum pipe bent, broken, or clogged. Blocked air inlet. Air valve sticking in power piston.
- Power Unit Operates But Braking Action Not Normal - Fluid low. Glazed, dirty, or oily linings.