Coolant overhaul failure

[Ricky Bobby]

if you also want to lower the pressure in the system a bit, consider installing one of these on your next overhaul:

Buy G.A.S. BMW 1.2 Bar Coolant Cap

[Doru]

BMW recommends a coolant flush every 2 years - the inhibitors wear out, and it seems they affect the plastic life as well (and aluminum)
The plastic components of the cooling system get brittle, this is why you have to change all of them when you do the cooling overhaul. Some components might "look" good, but when you remove the hoses (sometimes they come off with a little of persuasion), you induce more stress, or even a crack without realizing it, and next you know is a leaking component.

Also, for these plastic parts, it's best to get the OEM from dealer. Not the "equivalent" that have the "correct" brand, but are made in PRC or God knows where, and will fail rather quickly.

0.02