Checking Pressure Drop In Cooling System:
WARNING: This page is about a different car, the 2005 BMW 645Ci and 2004 BMW 645Ci. However, it is still accessible from the selected car via links, so may be relevant.
Open cap on coolant expansion tank. Fit special tools 17 0 101 / 17 0 113.
Build up gauge pressure of 2 bar, wait approx. 2 minutes.
Cooling system is impervious to leaks if pressure drop is max.
0.1 bar.
Courtesy of BMW OF NORTH AMERICA, INC.