F 250 2WD Super Duty V10-6.8L (2009)
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If specified vacuum is not available, continue with Step 4.
4. Disconnect the engine side vacuum hose from the check valve and verify that the specified vacuum is available at the hose with the engine at idle
speed and the transmission in NEUTRAL.
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If specified vacuum is available, stop the engine, install a new check valve and continue with Step 5.
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If specified vacuum is not available, stop the engine, connect the vacuum hose to the check valve and refer to Engine to diagnose the no/low
vacuum condition. See: Engine, Cooling and Exhaust/Engine/Testing and Inspection
5. Apply the brake pedal several times to exhaust all vacuum from the system.
6. Apply the brake pedal and hold it in the applied position. Start the engine and verify that the brake pedal moves downward after the engine starts.
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If the brake pedal moves, the brake booster is operating correctly.
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If the brake pedal does not move, install a new brake booster.
7. Operate the engine a minimum of 20 seconds at idle. Stop the engine and let the vehicle stand for 10 minutes, then apply the brake pedal. The
brake pedal feel should be the same as that noted with the engine operating.
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If the brake pedal feels hard (no power assist), install a new brake booster check valve and retest.
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If condition still exists, install a new brake booster.
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If the brake pedal feels the same as noted with the engine operating, the check valve is functioning properly.
Brake Master Cylinder - Bypass Condition
Component Tests
Brake Master Cylinder - Bypass Condition
1. Disconnect the brake tubes from the master cylinder.
2. Plug the outlet ports of the master cylinder.
3. Apply the brakes. If brake pedal height cannot be maintained, the brake master cylinder has an internal leak and a new brake master cylinder must
be installed.
Brake Master Cylinder - Compensator Port
Component Tests
Brake Master Cylinder - Compensator Port
1. With the vehicle in NEUTRAL, position it on a hoist.
2. Apply and release the brakes.
3. With the brakes released, attempt to rotate each wheel and check for any brake drag.
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If an excessive amount of brake drag exists at multiple wheels, continue to Step 4.
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If an excessive amount of brake drag exists at only one wheel, it indicates a possible seized brake caliper, brake wheel cylinder or parking
brake component. Repair or install new components as necessary.
4. Check the brake stoplamp switch and the brake pedal free play to verify that the brake pedal is not partially applied.
5. Loosen the brake master cylinder nuts and position the brake master cylinder away from the brake booster.
6. With the brakes released, attempt to rotate each wheel and check for any brake drag.
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If the brake drag is no longer present, install a new brake booster.
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If the brake drag is still present, install a new master cylinder.
Brake Booster
