How to Test an Auto's Thermostat

An automobile thermostat is designed to keep your engine at a constant temperature. Thermostats come in various heat ranges, since different engines operate more efficiently at different temperatures. In general, the thermostat blocks the cooling system from circulating until the coolant in the engine block gets hot enough to necessitate cooling. At a designated temperature the spring opens the thermostat and allows the coolant to circulate. Should the thermostat fail to open, the engine may experience severe damage.

Instructions

1

Start the vehicle and let it run. Turn the heater and blower on. Aim an inferred thermometer at the heater vent and monitor the temperature of the air blowing from the vent.

2

Record the temperature of the air stream from the heater vent as soon as the thermostat opens. Heat will be felt immediately. The recorded temperature from the infrared thermometer should be within close proximity of the temperature at which the thermostat opened.

3




Follow the top radiator hose to the hose neck on the engine block. The thermostat is under the hose neck.

Remove the thermostat from the engine if it failed to open. Place a drain pan under the radiator drain cock, open it and drain a gallon of coolant from the radiator.

4

Remove the two bolts that hold the radiator hose neck to the engine block, using a 9/16-inch socket and ratchet. Pull the brass colored thermostat from the engine block.

5

Inspect the bottom of the thermostat for the specific temperature that is stamped into the metal. For example: Thermostats range in temperature from, 160 degrees to 195 degrees.

6

Place a pan full of water on top of a stove. Put the thermostat that was removed from the engine into the pan. Insert a cooking thermometer into water and heat the water to the temperature stamped on the thermostat. At the specified temperature the thermostat spring should open the thermostat. If not discard and replace the thermostat.