There are MANY sizes of bottles, just saying "one bottle" is not helpful.
2"
Drain the radiator. Remove the radiator hose. Remove the inlet from the engine. The thermostat is in the inlet. Replace the inlet and the gasket, and reverse the procedure to finish the procedure.
The thermostat should be on the top of the engine under the water inlet. Drain the radiator. Remove the top radiator hose from the inlet. Unbolt the inlet, and pull the thermostat out for replacement.
to close the water inlet after the cistern is full
Drain the radiator. Remove the top hose, and the water inlet. Remove the thermostat from under the inlet, and replace it. Reverse the steps to finish the installation.
Drain the radiator. Remove the top radiator hose and water inlet. Remove the thermostat from under the inlet. Install the new thermostat, reinstall the inlet and hose, and fill the system with new freon.
Drain the radiator. Remove the lower radiator hose from the motor. Unbolt the hose inlet, and remove the thermostat. Replace the thermostat and the inlet, the hose, and refill the radiator.
drain or gully may have another inlet coming into same pipe via a junction under the floor
Drain the radiator and dispose of the coolant as its toxic to animals. Remove the top radiator hose, and water inlet. Remove the thermostat from under the inlet and replace it. Reinstall the inlet and top hose then fill the system with new coolant.
From the rim of the drain inlet to the p-trap point of connection 15 inches is what I recall.
To replace the thermostat on a 91 Cavalier you need to drain the radiator. Remove the top radiator hose and water inlet. Remove the thermostat from under the inlet. Install the new thermostat and reinstall the inlet and hose. Fill the radiator with fresh antifreeze.
Drain the Cavaliers radiator. Remove the top radiator hose, and the inlet pipe. Take the thermostat out from under the inlet pipe and replace it. Reinstall the pipe and hose, then refill the radiator.