Thermostat inspection includes examining which parts?

• A. Thermostat, bypasses, housing, and seals
• B. Radiator cap and hoses
• C. Timing belt
• D. Spark plug wires

Answer: (A)

Inspecting a thermostat centers on the parts that directly control coolant flow and sealing around that control point. The thermostat itself is checked to ensure it opens and closes at the correct temperature, so coolant flow is regulated properly. The bypass path is examined because it allows coolant to circulate even when the thermostat is closed, preventing hot spots and aiding warming up. The housing is inspected for cracks or damage where the thermostat sits, and the seals or gaskets are checked to ensure there are no leaks at the junctions. If any of these components are worn or failing, coolant flow can be restricted or leaks can occur, leading to improper engine temperature. Other cooling-system items like the radiator cap and hoses are important for pressure and circulation but aren’t part of the thermostat assembly; timing belt and spark plug wires relate to timing and ignition, not thermostat operation.