Which item is NOT listed as a common cause of problems in hydraulic actuators?

• A. Overheating
• B. External leakage
• C. Internal leakage
• D. Sluggish operation

Answer: (A)

The key idea here is identifying which faults are routinely listed as common trouble sources for hydraulic actuators. External leakage, internal leakage, and sluggish operation are classic, well-known issues: external leakage points to worn seals or fittings and shows up as visible fluid loss; internal leakage means fluid bypasses intended paths inside components like seals, pumps, or valves, reducing force or speed; sluggish operation points to problems such as contamination, clogged passages, or sticking valves that slow the actuator.

Overheating, while it can degrade performance by changing oil viscosity or harming seals, is not typically listed as a primary, common fault cause in many diagnostic guides. It’s more often a consequence of overloading, insufficient cooling, or fluid degradation rather than a fundamental fault mode like leaks or jammed/blocked flow. So overheating isn’t treated as one of the standard common causes, which is why it’s the best choice for not being listed.