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206-06-16 Hydraulic Brake Actuation 206-06-16 GENERAL PROCEDURES Adjustable Brake Indexing Brake Hose Replacement 1. Refer to Section 310-02. A flexible brake hose should be replaced if it shows signs of softening,cracking,leaks or abrasion. System Bleeding When installing a brake hose,position the hose to avoid contact with other chassis parts. 1. Refer to Section 206-00. Brake hoses should be installed as shown on the Power Brake Booster Testing installation drawings. 1. Check the hydraulic brake system for leaks or Hoses must not be twisted. insufficient fluid. New copper gaskets must be installed in all applicable 2. With the transmission in neutral, stop the engine locations. and apply the parking brake. Depress the brake Brake Tube Replacement pedal several times to exhaust all vacuum in the system. If a section of the brake tubing becomes damaged,the 3. With the engine shut off and all vacuum in the entire section should be replaced with tubing of the system exhausted, depress the pedal, and hold it same type,(special doublewall steel tubing conforming in the applied position. Start the engine. If the to specification ASTM-A 254-6T),size,shape and vacuum system is operating, the pedal will tend to length. Copper tubing should not be used in a fall away under foot pressure and less pressure hydraulic system. will be required to hold the pedal in the applied Brake lines should be installed as shown on the position. If no action is felt, the vacuum booster installation drawings. system is not functioning. Use Special Tools when bending brake tubing to fit 4. Remove the vacuum hose from the brake booster underbody or rear axle contours.Be careful not to kink check valve connection. Manifold vacuum should or crack the tube. be available at the check valve end of the hose All brake tubing should have the ends formed identical with the engine at idle speed and the transmission to the existing ends (using Special Tools)to provide in neutral. Be sure that all unused vacuum outlets leak-proof connections.Clean the brake tubing by are properly capped, hose connectors properly flushing with clean brake fluid before installation. secured, and that vacuum hoses are in good condition. When it is established that manifold vacuum is available to the booster, test the check valve and replace if necessary. With the engine shut off disconnect the vacuum hose from the check valve. Connect a piece of tubing to the check valve and blow into the check valve. No air should pass through the valve. Connect the vacuum hose to the booster and repeat Step 3. If no downward movement of the brake pedal is felt, replace the brake booster. 5. Operate the engine a minimum of 10 seconds at fast idle. Stop the engine and let the vehicle stand for 10 minutes; then, depress the brake pedal with approximately 80 N force. The pedal feel (brake application) should be the same as that noted with the engine operating. If the pedal feels hard (no power assist), replace the brake booster. NOTE: If the brake pedal movement feels spongy, bleed the hydraulic system to remove air from the system. Hydraulic Line Repair Always bleed the applicable primary or secondary brake system after hose or line replacement. illustrations. G22115 en |