Your MK6 needs a water pump. The propeller is plastic and comes apart from the metal shaft and doesn't spin. Causing the flow of coolant to stop moving thru the radiator.
If that were true why does the heater still cool the engine? Coolant wouldn’t flow through that radiator either if it were the pump. No circulation would also mean no heater.
Should’ve added: sitting in front of the car the other day I noticed the radiator has had a rough life. Car may have been towed behind an rv or something most it’s life. Or they just played “ding the radiator with pebbles!” Too often
@@floki-man It does spin, but not at the same speed. To check this, when it goes over the center line on the temp gauge. Put the car in neutral and rev the engine to about 5,000 rpm a few times and the temp will go down. Or drive around in second gear and keep an eye one the gauge.