Visual Inspection
| • | Check for a cracked casting or brake fluid leaks around the master
cylinder. A leak will have at least one drop of fluid. A damp condition is
normal. |
| • | Check the pedal linkage for binding and for incorrect pushrod
length. Disassemble the master cylinder if you do not find improper brake
pedal travel or brake pedal binding. |
Low Pressure Check
This procedure inspects the following conditions:
| • | Component bore integrity |
- With the ignition switch in the OFF position, pump the brake pedal
in order to relieve the vacuum.
| • | Pump the brake pedal five times for vacuum-assisted brakes. |
| • | Pump the brake pedal twenty-five times for hydraulic-assisted
brakes. |
- Apply the brake pedal slowly (approximately 3 mm {1/8 in}
per second). This generates pressure in the master cylinder.
- Gradually increase pedal force. Observe for gradually increasing
brake pedal travel (Falling Away).
- If the brake pedal travel tends to gradually increase, preform
the High Pressure Check.
- If the High Pressure Check does not locate a leak, then the master
cylinder has an internal leak.
High Pressure Check
This procedure tests for the following conditions:
| • | Leaks at the following locations: |
- With the engine running, apply the brake pedal slowly (approximately
3 mm {1/8 in} per second). This generates pressure in the master
cylinder.
- Gradually increase pedal force. Observe for gradually increasing
brake pedal travel (Falling Away).
- Check for evidence of external fluid leaks. Examine the following
items:
- If you observe fluid around any component, that component has
failed and needs to be replaced.
- If you find a leak at a connection, tighten the connection to
specification, Refer to
Fastener Tightening Specifications
.
- Perform the High Presssure Check again.
