Hello janie g 01,
Here is some info that should help you.
Engine Coolant Thermostat Replacement
Universal Clamp Pliers
Important: During extremely cold weather, -12°C (+10°F) or colder, the engine's coolant temperatue will decrease quickly when idling with the heater fan on high speed, and cool air may flow from the heater outlet.
Important: The O-ring gasket must be replaced whenever the thermostat housing is removed.
Important: The thermostat element should not be removed if the assembly requires testing.
Notice: The thermostat will not function correctly once it is contacted by oil. If oil is found in the cooling system, it must be flushed and the thermostat's cartridge replaced.
Notice: Use extreme care and do not damage or scratch the machined aluminum surfaces. Leaks will result.
Important: Make sure the element's retaining tangs are properly seated in the two legs and the element piston is correctly positioned in the water inlet housing.