What is the common fault?
Perhaps the most obvious initial sign of a problem is a rattling noise from the VANOS unit itself, found at the front top of the engine where you’ d find the cam sprockets. Of course, as VANOS is an integral part of how the engines are designed to run, a faulty system can affect performance. With no change in cam timing – when the system has completely failed – you can feel a loss of power, rough idling and reduced fuel economy. A broken VANOS unit will also cause the engine management light on the dashboard to illuminate.
The S54 is perhaps the VANOS of choice for multiple failures. In these engines, the camshaft sprocket bolts can shear and the integrated high-pressure oil pump driven by the camshaft that the entire system relies upon, can break its driving tabs. BMW included too much play between the pump disc and the tabs in the hub from the factory, and that only increases over time.
The VANOS system is located in an easily accessible place at the front top of the engine
60 The Engine Rebuilder Issue 01