I understand a cooling system. But there is nothing wrong in questioning german engineering once in a while. Recalls are exactly that; admitting something is wrong and replaced by something that will help resolve a repetitive fail.
Ok , granted , there is no recall for the cap but sometimes the majority is right and german engineering is wrong. Not saying this is what is happening in this case and I will probably end up with the 2bar cap this morning.

Expansion tank failure???? What a farce!!!

__________________
His : 2005 X5 4.8is (SOLD)
Hers: 2007 X5 3.0si (SOLD)
_______________
Retired:
1999 518
2000 323i
2002 M3 (beautiful car)
2003 330Ci