How is the hydraulic brakes leak check performed?

The hydraulic brakes leak check is performed by pumping the brake pedal three times and then holding pressure on the pedal. This method is effective in diagnosing potential leaks in the hydraulic brake system. When you pump the brake pedal, it builds up hydraulic pressure within the system. Holding the pedal in position while applying pressure allows you to feel for any loss of pressure over time, which would indicate a leak. If the pedal slowly sinks to the floor, this is a clear sign that there may be a problem in the hydraulic system, such as air in the lines or a leak in the master cylinder or brake lines.

In contrast, other methods listed do not effectively test for leaks. Pumping the brake pedal once or twice does not provide enough pressure buildup to determine if a leak exists, and continuously pumping the brake pedal does not allow for the measurement of any drop in pressure, which is critical for identifying leaks.