Pinpoint Test F: Testing

F1 CHECK THE BASE BRAKE COMPONENTS
- Visually inspect the brake lines from the hydraulic control unit (HCU) to the wheel cylinders.
- Visually inspect the calipers and the brake components.
- Are any of these components damaged or leaking?
1. YES : REPAIR as necessary. REFER to BRAKE SYSTEM - GENERAL INFORMATION to continue diagnosis of the base brake system.
2. NO : Go to F2.
F2 CHECK FOR A LEAKING DUMP VALVE
- Key in START position.
  
  Fig 1: Checking For Leaking Dump Valve
  Courtesy of FORD MOTOR CO.
- Remove the rubber caps from the 2 HCU low pressure accumulators and insert a clean steel implement (such as a paper clip) into each low pressure accumulator.
  NOTE: A leaking dump valve is similar to the master cylinder bypass condition. It is important that the pedal be quickly and forcefully applied to rule out the master cylinder bypass as a cause. Typically a master cylinder bypass occurs only at low pedal pressure rates and low tire pressures.
- Have an assistant press hard on the brake pedal while observing the steel implements.
- Do any of the steel implements move out 12.7 mm (0.5 in) or more?
1. YES : INSTALL a new HCU. REFER to Hydraulic Control Unit (HCU) .
2. NO : System is operating correctly at this time. REMOVE the steel implements and INSTALL the rubber caps. CLEAR the DTCs. DRIVE the vehicle over rough roads. REPEAT the self-test.