Power Brake Unit Test

WARNING: This page is about a different car, the 1996 Lexus SC 300 and 1995 Lexus SC 300. However, it is still accessible from the selected car via links, so may be relevant.

Release parking brake. With engine running, depress brake pedal and measure pedal reserve distance. Reserve distance is distance from floor pan to brake pedal when fully depressed. See MINIMUM BRAKE PEDAL RESERVE DISTANCE SPECIFICATIONS .
If reserve distance is incorrect, bleed brake system, and recheck reserve distance. Depress brake pedal several times with engine off, and ensure pedal reserve distance does not change. Depress brake pedal, and start engine. If brake pedal goes down slightly, power brake operation is normal.
Start engine, and run it at idle for 2 minutes. Depress brake pedal several times slowly. If pedal goes down farther first time and then gradually rises after second or third time, power brake unit is airtight. If pedal does not act as described, go to next step.
Depress brake pedal while engine is running. Stop engine with pedal depressed. If pedal reserve distance does not change after holding pedal down for 30 seconds, power brake unit is okay. If pedal sinks, replace power brake unit.

MINIMUM BRAKE PEDAL RESERVE DISTANCE SPECIFICATIONS

Application

⁽¹⁾ In. (mm)

SC300

3.50 (89)

⁽¹⁾	At 110.2 lbs. (50 kg).