ABYC Diesel Practice Exam

During troubleshooting, what indicates that coolant is escaping due to a non-mechanical failure?

1. Oil contamination in coolant

2. Raw water pump impeller failure

3. Excessive pressure in the system

4. Coolant overflow not related to overheating

The correct answer is: Coolant overflow not related to overheating

When troubleshooting a cooling system, identifying why coolant is escaping is crucial for effective repairs. The scenario where coolant overflow occurs not related to overheating is indicative of a non-mechanical failure. This situation can often arise from issues such as a faulty radiator cap, which might not be holding pressure, or a malfunctioning coolant recovery system. In these cases, the coolant can overflow due to the system's inability to maintain proper pressure and temperature regulation, rather than a direct mechanical failure like a leak or crack in the cooling system components. In contrast, oil contamination in coolant generally points to a breach between the oil and coolant systems, typically from a failing heat exchanger or engine component, signifying a more mechanical failure. A raw water pump impeller failure typically leads to a loss in the system's ability to circulate coolant effectively, which can lead to overheating and may not be classified as a non-mechanical failure. Excessive pressure in the system often indicates blockages or mechanical damage, leading to further mechanical issues. Thus, the overflowing of coolant without overheating signals a failure in the system's design or component functionality rather than a physical failure of the mechanical parts involved.