RDX L4-2.3L Turbo (2008)
Vacuum Brake Booster: Testing and Inspection
Brake Booster Test
NOTE: The brake boost system is assisted by an electric vacuum pump. If the electric vacuum pump system indicator stays on, check the electric
vacuum pump system before you test the brake booster. If the indicator comes on when testing the brake booster, there is no problem. Just check for
and clear any DTCs with the HDS.
Functional Test
1 With the engine off, press the brake pedal several times to deplete the vacuum reservoir, then press the brake pedal hard, and hold it for 15
seconds. If the brake pedal sinks, either the master cylinder is leaking internally, or the brake system is leaking. Inspect the brake hoses and lines.
2. Start the engine with the brake pedal pressed. If the brake pedal sinks slightly, the vacuum booster is operating normally. If the brake pedal height
does not vary, do the leak test.
3. Do the brake system test.
Leak Test
1. Press the brake pedal with the engine running, then stop the engine. The brake pedal height should not vary while pressed for 30 seconds. If the
pedal height rises, go to step 6. If it does not rise, go to step 2.
2. Start the engine and let it idle for 30 seconds. Turn the ignition switch off, and wait 30 seconds. Press the brake pedal several times using normal
pressure. When the pedal is first pressed, it should be low. On consecutive applications, the pedal height should gradually rise. Does the pedal rise
on each consecutive application? If it rises, the booster is OK. If it does not, go to step 3.
3. Disconnect the brake booster vacuum hose (A) from the 3-way joint (B). A check valve (intake manifold) (C) is built into the hose.
4. Start the engine, and let it idle. Check for vacuum on the brake booster vacuum hose with your finger. If no vacuum is available, the check valve
(intake manifold) is not working properly. Replace the brake booster vacuum hose and check valve (intake manifold), and retest. If vacuum is
found, go to step 5.
5. With the engine off, reconnect the vacuum hose to the 3-way joint.
6. Start the engine, and then pinch the brake booster vacuum hose between the 3-way joint and the booster.
7. Turn the ignition switch off, and wait 30 seconds. Press the brake pedal several times using normal pressure. When the pedal is first pressed, it
should be low. On consecutive applications, the pedal height should gradually rise.
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If the pedal position does not vary go to step 8.
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If the pedal position varies, replace the brake booster vacuum hose/check valve (intake manifold) assembly.
8. Start the engine, and pinch off the booster vacuum hose between the 3-way joint and the electric vacuum pump.
9. Turn the ignition switch off, and wait 30 seconds. Press the brake pedal several times using normal pressure. When the pedal is first pressed, it
should be low. On consecutive applications, the pedal height should gradually rise.
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If the pedal position does not rise, inspect the seal between the master cylinder and booster. If the seal is OK, replace the brake booster.
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If the pedal position varies, inspect the vacuum hose between the 3-way joint and the electric vacuum pump check valve. If the hose is OK,
replace the vacuum hose/check valve (vacuum pump).
