Checking pressure drop in cooling system
WARNING: This page is about a different car, the 2013 BMW 550i GT, 2012 BMW 550i GT, 2011 BMW 550i GT, and 2010 BMW 550i GT. However, it is still accessible from the selected car via links, so may be relevant.
Open the sealing cap on the coolant expansion tank. Mount special tool (1) 17 0 101 and (2) 17 0 113 from the set of special tools 17 0 100.
Build up EXCESS PRESSURE and wait approx. 2 minutes.
Cooling system is impervious to watertightness if pressure drop is max. 0.1 bar.