88M Tractor Trailer and HEMTT Practice Test 2025 - Free Practice Questions and Study Guide

When the engine coolant temperature gauge reads over 219 degrees, the proper course of action is to shut down the engine immediately. Maintaining optimal operating temperatures is crucial for engine performance and longevity, and temperatures exceeding 219 degrees can indicate that the engine is overheating.

Shutting down the engine halts any further damage that high temperatures could cause, such as warping of engine components or failure of the cooling system. After the engine has been turned off, further investigation into the cause of the overheating can be conducted, such as checking coolant levels, inspecting for leaks, or looking at the radiator and fan operation.

Idling the engine, which is suggested in the initial choice, may not adequately address the issue and could lead to more severe engine damage. Increasing RPMs or activating the cooling system while the engine is still in an overheated state can exacerbate the problem. Therefore, immediate shutdown is the most responsible and effective response to prevent further engine complications.