Easiest coolant change ever!
Just did a coolant flush using this technique.
Drove for 20 mins to make everything hot, let it rest for another 20 mins so I could prepare the coolant mix and to more safely unscrew the cap and release the pressure in the system.
Then I removed the hose at the back of the coolant tank, the little nub on my hose was 11mm so I had bought a hose at the hardware store with an inner diameter of 10mm it slotted right over and was plenty secure.
Then I started the car with the climate control off, for the first few minutes nothing really came out, I waited and it started to flow. After it started to flow I turned on the heater to high and the fans to the lowest setting. It suddenly started to rapidly fill the coolant tank and it almost overflowed, I quickly turned off the engine and then it was quickly draining again, I started filling it up again to the max line. I turned on the engine once again and everything was fine and behaved as expected. (Maybe you start with the climate on hi, but then it takes longer for everything to reheat I guess) Not really exciting and not a deal breaker.
When everything was flowing and I was left with 1 Liter of coolant I turned of the engine, the water pump still kept flowing for 1-2 minutes so I was right in the money and I had nothing left but I was at the max line, but for the next time I will keep a larger reserve of around 2L. When everything stopped flowing I cloud reconnect the hose at the back of coolant tank.
In total I put in 10L and 10L came out for a 7.8L system, maybe it won’t be 100% fresh but it is good enough. Via this method you also don’t have any change of air getting in the system so that’s really cool!