I did it! A zero pressure cooling system.
Well, I decided that if I run a zero pressure cooling system, I may not have to do that next cooling system overhaul. No pressure, no exploding radiator.
So I ordered a case of Evans NPG+ waterless coolant. Not cheap at about $120, but if it saves an overhaul............... The case was 4 gallons. It took 12 liters (or about 2 3/4 gallons) to fill the system. That leaves over a gallon for top-ups, since you can't add water or any other kind of coolant with Evans.
I fully drained the system, radiator, lower hose, block drains, and ran the heater pump to get it out of there. I must have got it all because Bentley says it holds 12 liters and that is exactly what I got in it. So everything must have been out and there can't be any air trapped in there. After the NPG+ fill I changed the 2 bar cap for a 1.4 bar one.
With a boiling point of 375 degrees there should never be any pressure in the system now.
chiefwej 2003 540i ///m-tech 6-speed
Black Sapphire Metallic w/gray