It depends on the vehicle. However, where the thermostat sits in the cylinder head or top hose, most vehicles only require a partial drain.
One can change the thermostat on a Chevy car by draining the coolant and disconnecting the upper radiator hose. The thermostat housing is then unbolted, the old thermostat removed, and a new unit placed in the housing.
The thermostat on a 2004 Chevy Venture is changed by draining the radiator, removing the upper radiator hose, and unbolting the thermostat housing. The old thermostat and gasket can then be removed and replaced.
The thermostat is located under the engine where the lower radiator hose attaches to the engine block. Changing a thermostat is a relatively simple operation involving draining the cooling system and removing and replacing only 2 nuts. Since you are asking in this forum, you should probably have the job done by someone with experience working on automobiles. --Ken
If the engine is overheating or when you service the cooling system and change the antifreeze.
The thermostat on a 99 Mitsubishi Galant is changed by draining the coolant, removing the upper radiator hose, and unbolting the housing. The thermostat can then be removed and a new one put into place.
Drain the water from the cooling system. Remove the water supply line to the thermostat. Remove the thermostat housing bolts. Remove the thermostat. Reverse the process to install the new thermostat.
There is no recommended interval, but if you are draining the system for any reason, that would be a good time to do so.
Drain the water from the cooling system. Remove the water hose from the thermostat housing. Remove the thermostat housing retaining bolts. Remove the thermostat. Reverse the process to install the new thermostat.
To change the thermostat in a 2002 Nissan Xterra, remove the bolts that hold the cooling fan in place. Lift the fan out of the vehicle and loosen the clamp holding the lower radiator hose to the thermostat housing with a wrench. Remove the thermostat out of the mounting and replace.
Drain the water from the cooling system. Remove the water supply hose. Remove the thermostat housing retaining bolts. Remove the thermostat. Reverse the process to install the new thermostat.
The thermostat on a 2005 Chevy Equinox is changed by draining the radiator, removing the upper radiator hose, and unbolting the radiator housing. The old thermostat can then be removed, a new gasket installed, and the housing bolted down.
Drain the water from your 1995 Chevrolet Corsica cooling system. Remove the water supply hose from the top of your thermostat housing. Remove the thermostat housing retaining bolts. Lift the old thermostat out and drop in the new thermostat.