Final answer:
To diagnose a defective water pump, observing residue at the pump's drain hole, seeing a coolant leak, and using a pressure tester are valid methods. Hearing a groaning noise at cruising speeds usually does not indicate a water pump issue but rather other vehicle components like the transmission or wheel bearings. The correct option is hearing a groaning noise at cruising speeds
Step-by-step explanation:
A diagnosis of a defective water pump can be done through multiple indicators, but not all methods are appropriate. Observing residue at the water pump drain hole, witnessing a coolant leak from the water pump, and usage of a pressure tester are all valid methods to diagnose a defective pump. However, hearing a groaning noise at cruising speeds is not a typical way to diagnose a problem with a water pump.
Groaning noises at cruising speeds can be indicative of various issues, such as problems with the car's transmission, wheel bearings, or differentials, but they are not generally associated with water pump failure. Symptoms of water pump failure usually involve overheating, visible coolant leaks, steam from the radiator, or a whining sound from the pump area itself due to a worn-out bearing.
A pressure tester is one of the most reliable tools to check for leaks and the integrity of the cooling system, including the water pump. This tool will pressurize the system without the engine running, which can help point out leaks that might not be easily visible otherwise.