2000 Acura TL Rising Temperature Gauge

Have your mechanic perform a chemical test for a leaking cylinder head gasket. If combustion gases pool under the thermostat, that will prevent it from opening.

Did you bleed the air out of the cooling system while refilling the coolant?

Might be time to consider finding a different mechanic. This is a basic tool that all shops have. You want to do business with a shop that keeps up-to-date with equipment and advanced training.

Most auto parts stores that rent or borrow tools will have this tester, but they will make you buy your own bottle of the special fluid. That is because it will be rendered useless if it freezes or gets contaminated with antifreeze. They don't want to risk having you return it with contaminated fluid for the next person.

The test involves drawing air from the radiator through a glass cylinder with two chambers partially-filled with a special dark blue liquid while the engine is running. If combustion gases are present due to a leaking cylinder head gasket, the liquid will turn bright yellow.