2000+ Toyota and Lotus cars are notoriously hard to fill with coolant after an engine or radiator replacement or even after simply disconnecting a hose and losing some coolant. The only proven way to get the cooling system filled right the first time is with a vacuum fill kit. It draws all of the air out of your cooling system then injects coolant to fill the system completely, no air bubbles.
If air remains in the system after you fill it with coolant (if you don’t use this tool) you may notice the heater not working. This is because an air bubble has found its way to the water pump and no coolant is circulating. The temperature gauge may not warn you that the engine is overheating and you could experience a catastrophic failure. Don’t risk your expensive engine!
All you need is a jug of coolant, this tool kit and an air compressor. Even a small compressor is fine.