Open the hood of your car and locate the thermostat housing. Do this by following the largest hose at the top of your radiator until it connects onto the thermostat housing on the engine block of the Pontiac.
Position your clean container under the radiator of the Pontiac, then use the flat-blade screwdriver to loosen the clamp on one of the lower radiator hoses. You will be draining the coolant from the radiator, so make sure that the container is positioned to catch the coolant once the hose is removed from the radiator.
Loosen and disconnect the bottom hose from the Pontiac's radiator and allow the coolant to drain into the container. Once it has stopped draining, set the container to the side. You will be refilling the radiator with this same fluid once the thermostat has been replaced.
Loosen the hose clamp on the Pontiac's thermostat housing hose with the flat-bladed screwdriver, then remove the hose from the thermostat housing. This is to give you access to the bolts securing the housing to the engine block.
Loosen and remove the bolts securing the thermostat housing to the engine block with the ratchet and sockets, then pull the thermostat housing away from the engine block to expose the thermostat underneath.
Use a razor blade to scrape away the remains of the old thermostat gasket from the bottom of the Pontiac's thermostat housing and from the engine block. Make sure to get it as clean as possible, as any residue may prevent a complete seal from being made and may result in a coolant leak.
Make a careful note of how the thermostat is oriented in its setting. You will need to install the new thermostat so that it is oriented in the same way. Once you have made note of this, remove and discard the Pontiac's old thermostat.
Apply a layer of gasket sealer compound to the bottom of the Pontiac's thermostat housing so that it is of uniform thickness. Once this is done, press the new thermostat gasket against the gasket sealer so that it sticks there.
Install the Pontiac's new thermostat so that it is oriented in the way you made note of in Step 7.
Place the thermostat housing carefully over the Pontiac's new thermostat so that you do not dislodge the thermostat gasket. Once this is done, secure it tightly using the bolts you removed in Step 5.
Reconnect and tighten the hoses you disconnected throughout this process, then open your radiator and pour back in the coolant you drained in Step 3. Once you have completed this step, the new thermostat will be ready for operation.