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MASTER CYLINDER DESCRIPTION MASTER CYLINDER The master cylinder body is made of aluminum and OPERATION MASTER CYLINDER The master cylinder bore contains a primary and secondary piston. The primary piston supplies hydraulic pressure DIAGNOSIS AND TESTING MASTER CYLINDER/POWER BOOSTER Note: Inspect and repair any external fluid leaks before performing test. 1. Start the engine and inspect the booster vacuum hose connections. A hissing noise indicates a vacuum leak. Correct any vacuum leaks before proceeding. 2. Stop the engine and shift the transmission into Neutral. 3. Pump the brake pedal until all the vacuum reserve in the booster is depleted. 4. Press and hold the brake pedal under a light foot pressure. The pedal should hold firm, if the pedal falls away the master cylinder or HCU may be faulty (internal leakage). 5. Start the engine and note the pedal action. It should fall away slightly under a light foot pressure and then hold firm. If no pedal action is discernible, power booster, vacuum supply, or vacuum check valve is faulty. Proceed to 6. If the POWER BOOSTER VACUUM TEST passes, retest the booster vacuum reserve as follows: Release the brake pedal. Increase the engine speed to 1500 rpm, close the throttle and then turn off the engine. 7. Wait a minimum of 90 seconds and try the brake action again. The booster should provide two or more vacuum assisted pedal applications. If the vacuum assist is not provided, some component of the booster is faulty. ZH BRAKES - BASE 5 - 45 |