Note: This test requires a pressure gauge capable of measuring liquid pressure up to 50 bar.
1. Apply the handbrake, then raise the front of the vehicle and support it on axle stands.
2. Unscrew the bleed valve on one of the front brake calipers, connect the pressure gauge to it. Pump the pressure gauge if necessary.
3. Install an adjustable brake pedal compressor between the driver's seat and the pedal, depress the pedal until the gauge reads 50 bar.
4. Within 45 seconds, pressure drops should not exceed 4 bar. If the difference is greater, first check for leaks in the hydraulic line, master cylinder and calipers. If they are OK, replace the hydraulic modulator.
5. Reduce the pressure on the brake pedal until the pressure gauge shows 6 bar.
6. Over the next three minutes, pressure drops should not exceed 1 bar. If the differences are greater, replace the hydraulic modulator.
7. Remove the pressure gauge, install the bleeder fitting.
8. Bleed the hydraulic system as described in Chapter 17.
9. Lower the vehicle to the ground.
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