Drain the radiator into a suitable container. Remove the top radiator hose at the engine. That is the thermostat housing. Remove the 2 bolts and remove the thermostat. Clean the thermostat housing and the intake manifold and install the thermostat. It is not necessary to use silicone sealer but if you feel you must then use sparingly.
there is no such thing as a 1999 impala
It is on the intake manifold near the thermostat housing.
It is in the thermostat housing at the end of the top radiator hose on the engine side.
Drain the radiator in a container. Remove the engine end of the top radiator hose. The housing has 2 bolts that you remove. Remove the thermostat and clean the surfaces and reinstall the thermostat. Reinstall the hose and add coolant.
Drain the radiator down 1/2 way into a container. Remove the top radiator hose from the engine end. The housing is where the thermostat is located. Remove the 2 bolts and the housing. Remove the thermostat and clean the surfaces and install the thermostat.
It is on the intake manifold near the thermostat housing.
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no
What size engine.
It is located in the intake manifold near the thermostat housing.
A 2003 Impala does not have a timing belt. It has a chain.
FRONT OR REAR?