What is the consequence of a broken piston return spring in a brake master cylinder?

A broken piston return spring in a brake master cylinder primarily affects the proper function of the braking system. The return spring is crucial for ensuring that the piston returns fully to its resting position when the brake pedal is released. If this spring is broken, the piston may not return to its original position.

This malfunction can lead to the brakes being inadvertently engaged or held in a partially applied state, resulting in a locked brake condition. When the brakes lock, it can cause the vehicle to experience difficulty in moving or can create uneven tire wear and potentially lead to more dangerous driving situations.

In contrast, the other outcomes suggested—drags, seizes, or releases—do not accurately reflect the impact of a broken return spring in this context. "Drag" typically relates to brakes being continually applied, which can happen, but is more associated with other issues. "Seize" could imply a total failure of the brake system, while "release" would indicate that the brakes are functioning correctly, which is not the case when the return spring is broken. Thus, the most accurate consequence in this scenario is that the brakes would lock.