1. Stop engine and put the transaxle in neutral.
2. Pump the brake pedal several times until all vacuum boost is depleted.
3. Depress the brake pedal and hold a constant foot pressure on the pedal.

The hydraulic system may be leaking if the pedal gradually falls away with the constant pressure. Check the master cylinder fluid level

A slight drop in reservoir level results from normal lining wear. An abnormally low level in the reservoir may indicate a leak in the system.

The hydraulic system may be leaking internally as well as externally.

Refer to Master Cylinder Inspection steps 1 and 2. The system may appear to pass this test but still have a slight leakage.