What indicates that the engine is at normal operating temperature before performing a TSI?

• A. Radiator hoses are cold and pressure is low
• B. Upper and lower radiator hoses are hot and under proper pressure
• C. Cooling fans are off and radiator is cool
• D. Engine temperature gauge is at 50 C

Answer: (B)

When an engine reaches its normal operating temperature, the cooling system is actively circulating hot coolant and is under proper pressure. The clearest sign of this is that both the upper and lower radiator hoses feel hot to the touch and the cooling system is maintaining the expected pressure. This combination shows the thermostat has opened, coolant is flowing, and the engine has reached its designed temperature range.

Other signs don’t reliably indicate a warm engine: cold hoses with low pressure mean the engine is still cold; a radiator that’s cool and fans off can occur if the engine hasn’t warmed yet or the thermostat isn’t allowing flow; a gauge reading of about 50 C is well below typical operating temperature, since most engines run around 80–100 C when fully warmed.