Not 100% sure on a 2008 4/4 but later models have the full amount of coolant circulating all the time. This because the heater core is permanently fed, with dash cabin heat control operating flaps in heater/air box which adjusts the mix.
Richard
2018 Roadster 3.7 1966 Land Rover S2a 88 2024 Royal Enfield Guerrilla 450 1945 Guzzi Airone
