Hi I have a Range Rover 3.6tdv8 my problem was today the temperature gauge shot up and I got a warning with reduced power
I pulled over and the coolant was at the very top because I haven’t had the heater on for weeks as it is warm over here I put on heat to max the coolant went way down in level I carefully removed cap to let steam out and the needle went back to normal
What do you think my problem is how can turning on the heat instantly put my temperature gauge back to normal

Thanks in advance