I replaced every part of my cooling system in 10/2020. I think I bought two gallons of 100% BMW coolant. I have read on this forum just to go with BMW coolant (+ distilled water) and you won't have any issues.

And the two gallons of distilled water. You may not use it all. But I wanted to keep some 50/50 on hand in case any leaks developed.

 

DId you use the full 2 gallons of coolant or how much does the system take?

 

Also, here's the most helpful bleeding video:

 

Also here:

325ci Slowly Overheating

I have a 2005 325ci and it has been slowly overheating especially when driving on the street. I have replaced both belts, put a new radiator in, replaced both rad hoses, got a new power steering return hose AND even got a new clutch fan since I thought that was the culprit. All of these...

www.e46fanatics.com

 

ISTA says not to bleed the S54

If you follow the drain and refil method, it's much more effective
Drain, refill and run engine 2 or 3 times with distilled water this, will ensure most of the coolant has been diluted and the system is clean running on distilled water
once drained for the 2nd or 3rd time, fill the system with 5 litres of BMW coolant, then top up with distilled water as per ISTA picture below