Here is a suggestion to prevent a cooling system blowout in your N62. Drain the BMW coolant(Manufactured by Valvolene/Ashland). Use Pentosin NF or Motul Inugel Expert Ultra. Neither of these has Ethylhexanoic Acid which is a plasticizer. Remove 2 bar coolant recovery cap and throw it in the trash. Then buy/install a GENUINE BMW 1.4 bar cap from a 2007 335i. Fill coolant recovery tank to minimum mark to leave room for expansion. Also use only Genuine BMW water pumps with composite rotor as these are there to prevent electrolysis and bearing wear, not for cheapness. Every aftermarket coolant cap I have come across does not function properly as well. If the 2 arrows do not line up when locking down the cap, do not use it. Every defective aftermarket cap I have seen including Febi brand are made in China. Buy your coolant cap at the stealer, don't be cheap.