The easiest way to fill the Lotus Elise range coolant system is by using vacuum.
Any work on the radiator, condensor or radiator fans requires the coolant system to be fully drained as the radiator stack needs to be taken off and put upside down. Also an engine out job can only be performed with an empty cooling system.
A coolant purge and refill system helps to get the air out of the radiator, sill pipes and engine block without a big risk of remaining air pockets.
It requires an appropriate compressor and a vacuum purge system. The compressed air flow in a nozzle creates a vacuum (of approx 80% below ambient pressure).
A three way valve sequence first purges the coolant system to approx 0.8 bar below ambient [valve A open, valve B closed].
Then the vacuum source is closed [valve A closed], and the coolant container is allowed to be drawn into the coolant system [valve B open]. It may take a few cycles to fill it completely, but it is a few minutes job.
Start the engine, make a very short trip around the block and wait for the thermostat to open. Inspect coolant level at that time.