Final answer:
When testing for leaks in hydraulic brakes, one should pump the brakes 3 times and then maintain pressure for 10 seconds to check for consistent pressure and potential leaks.
Step-by-step explanation:
If testing your hydraulic brakes for leaks, the correct procedure to follow is A. Pump the brakes 3 times, then apply pressure for 10 seconds. This method helps in determining if there is a consistent pressure in the brake system or if there might be a loss of pressure indicating a leak. Hydraulic brakes operate based on Pascal's principle, where pressure applied at one point in a confined fluid is transmitted undiminished to all points in the fluid and to the walls of its container. This principle explains why a force applied to the brake pedal is intensified and then transmitted evenly to the wheel cylinders, causing the vehicle to slow down or stop.
To elaborate, when you pump the brakes, you are building up pressure in the system. After pumping, maintaining pressure on the pedal for 10 seconds allows you to feel for any softness or sinking of the pedal that would suggest a loss of pressure. If the pedal goes down further during this time, it indicates a probable brake fluid leak or an air bubble in the hydraulic system which needs to be addressed for safe vehicle operation.