Which of the following actions can cause brake systems to lose effectiveness?

Excessive heat from overuse is a major factor that can lead to a loss of effectiveness in brake systems. When brakes are applied repeatedly in a short period of time, such as during repeated hard braking, the components can heat up significantly. This heat can cause the brake fluid to boil, which may lead to reduced braking efficiency, a phenomenon known as brake fade. Additionally, excessive heat can damage brake components, including pads, rotors, and drums, leading to further performance issues.

In contrast, other actions like using engine braking are generally considered beneficial for maintaining brake effectiveness, as they help reduce the strain on the braking system by utilizing the engine's resistance to slow down the vehicle. Frequent stop-and-go traffic may cause wear over time but does not directly impact brake effectiveness in the same immediate way excessive heat does. Adjusting the brake balance is generally a maintenance task that aims to enhance braking performance rather than detract from it.