2001 Range Rover overheating

[LRTECH]

Sounds to me like you have an air pocket in the system (just guessing) it could also be many expensive items... but I am leaning toward and air pocket...

You will need to bleed the system.

Park with the front end up hill or parked on a set of ramps.
Fill the coolant system
Turn on the engine, and the heater
run till it gets warm, shut down
Fill the coolant system
Repeat until it will run warm and not require a refill.

you need to also open up the bleeder (looks like a bid plastic phillips head screw on coolant resevoir) when adding coolant. keep it open until it stops spitting out air and only flowing coolant.