1. Visual Inspection:
* Leaks: Carefully inspect the booster for any signs of vacuum leaks. Look for cracks, damage to the vacuum hose connections, or wetness around the booster (indicating a possible fluid leak, although this is less common).
* Hose Condition: Examine the vacuum hose connecting the booster to the intake manifold. It should be flexible, not cracked, brittle, or loose. Replace it if it's damaged.
2. Vacuum Test:
* Listen for Leaks: With the engine off, carefully remove the vacuum hose from the booster. Put your finger over the booster's nipple to feel for suction. If you feel strong suction and hold it for a few seconds, it suggests a good seal in the booster. If you hear hissing, you've got a leak *somewhere* in the system (booster, hose, or manifold connection).
* Gauge Test (More Accurate): A better method involves using a vacuum gauge. Connect the gauge to the booster nipple. With the engine running, the vacuum should read between 17-22 inches of mercury (Hg). A significantly lower reading could indicate a leak in the booster or elsewhere in the system. If the gauge reads zero or near zero, there's a significant problem.
3. Pedal Feel Test:
* Engine Off: Pump the brake pedal several times. It should feel firm and require considerable effort. If the pedal goes to the floor easily, it indicates a problem (but not necessarily *just* the booster).
* Engine On: With the engine running, pump the brake pedal again. There should be a noticeable difference: the pedal should feel much firmer and easier to press. If there's very little difference, the booster is likely faulty.
* Hard Pedal with Engine On: If the pedal is hard even with the engine on, the problem could be a vacuum leak (check all connections including the hose to the manifold), a master cylinder issue, or a problem within the booster itself.
4. Pedal Return Test (Less Common but Helpful):
* With the engine running, apply firm pressure to the brake pedal and hold it. Slowly release the pedal. It should return smoothly and swiftly to its original position. A slow or hesitant return could indicate internal booster issues.
Important Considerations:
* Other Components: Brake problems aren't always isolated to just the booster. Master cylinder failure, low brake fluid, worn brake pads/shoes, or other brake system components can mimic booster problems. If you are unsure about your diagnostic skills, it is best to take the vehicle to a qualified mechanic.
* Safety First: Be extremely cautious when working on the brake system. Properly depressurized brakes are crucial for your safety.
If the tests above point towards a bad power brake booster, it's crucial to replace it. A faulty booster compromises braking performance, significantly increasing the risk of accidents. Don't attempt to repair the booster itself; replacement is usually the most practical and safest solution.
