Checking pressure relief valve in cap
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2014 BMW X6, 2013 BMW X6, 2012 BMW X6, 2011 BMW X6, and 2010 BMW X6. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
While the vehicle is driven at high outside temperatures, the design may cause the pressure relief valve in the cap to open slightly and air together with dissolved coolant to escape. This coolant vapor condenses on the surface of the expansion tank and leaves traces when the vehicle has cooled down. These traces do not indicate whether the cap is defective or not. When the vehicle has been parked up for an extended period of time, the residual escaping coolant can cause the pressure relief valve in the cap to stick; therefore check the cap again 2 to 3 times.
Replace the cap only after you have checked three times and there is an incorrect opening pressure .
Screw cap (1) onto special tool 17 0 114.
Build up pressure with special tool (hand pump) 17 0 101; observe pressure gauge to ascertain when opening pressure is achieved.
Compare opening pressure of pressure relief valve .