How can a Smog Inspector ensure the engine is at normal operating temperature before conducting a TSI?

• A. Start the engine and drive for 5 minutes.
• B. Check the upper and lower radiator hoses for appropriate pressure, and that both hoses are hot.
• C. Wait for the engine to reach peak coolant temperature.
• D. Run the air conditioning to bring up the temperature.

Answer: (B)

Reaching normal operating temperature is shown by coolant circulating properly. When the engine warms up, the thermostat opens and hot coolant moves through the system. If you touch the radiator hoses and both are hot, that’s a clear sign the coolant is circulating and the engine has reached its typical running temperature. This confirms the engine is in the proper state for a TSI, so the emissions readings will reflect normal operating conditions.

Starting the engine and driving for a short time isn’t a precise check; the engine may not reach or stay at the ideal temperature for the test, and driving conditions can vary. Waiting for peak coolant temperature isn’t appropriate either, because you want normal operating temperature, not hotter-than-normal conditions, which can skew results. Running the air conditioning to raise temperature adds unnecessary load and doesn’t directly verify that the cooling system is at its normal operating temperature.

So, verifying that both radiator hoses are hot provides a direct, practical indicator that coolant is circulating and the engine has warmed to its intended operating state before performing the test.