Double Vanos is relatively simple to understand: in essence it is a continuous alteration of both inlet and exhaust cam shaft position based on engine speed and throttle opening. In essence a fully automatic “advance and retard” ....
If anyone can add more to this description, please do so!
Peter, you are probably aware that the VANOS shafts are adjusted by solenoids, which can fail if the oil seals on the shafts harden and cause a level of 'stiction' that the solenoids can't overcome. This has two implications:
1) drive your car regularly and hard !! Oil seals will stay flexible for longer if they do not dry out.
2) if buying an aftermarket warranty, be wary that the provider may need quite some persuading to accept that the VANOS shafts are effectively auxiliary camshafts (and therefore on the list of covered components) and not some weird item that is not on the list of parts covered. Mate of mine had quite the battle, but won in the end. Just saying...
