[makkan00]

I have done it last year. Few things to cosider;
1- Remove the under engine tray, or loose the front screws of under engine tray.
2- There is a second tray, which you may need to loose from one side.
3- If I am not wrong, the coolant drain is on passenger side.
4- There is white outer body with blue screw in it. DO NOT rotate the white body. Stabilize the white outer body and only undo the blue screw.
5- When blue screw is slightly loose, you'd ideally run the car. Turning on the heater with compressor will open all the passages. mm
6- Once the car reaches at running temp, with all the caution (gloves and etc etc), undo the blue screw and let the coolant drain.mm
7- Once it is flashed, add some distilled water to remove any traces of old coolant.
8- When you are satisfied that only distill water is coming, let it completely drain.
9- Put the blue screw back in.
10- Rear the method of opening all the passaged by TIS (I cannot remember it now).
11- Start adding the coolant. When it is full, run the car for few minutes.
12- Bleed the air bubles from the bleeding valves.
13- Let the car cool down and put all the screws back.

Check the coolant for next 2-3 days.

OEM BMW coolant is £20 on ebay but stealers sell them for approx £12 including VAT. You'd require ionized to make the coolant 50% diluted. Ionized water gives you max rust free coolant.

HTH.