Quote Originally Posted by hamish262001
Sounds like hyd lifters Every m50 and m52 I've had has done this to some degree, the correct grade of oil makes a big difference on these and also regular oil changes
So if it is I'm looking at re-shimming them? I used Castrol 10w40 last time I serviced her just under a year ago
Quote Originally Posted by Ketron
My bet is the tank vent valve, was giving issues on my M52B28. Couldn't for the life of my figure out where and what was causing the noise, eventually turned out to be the problem. Is actually common enough and BMW resigned it in later models. There is also a guide in TIS to remedy the problem if the owner complains

Put your hand on it and and if you can feel the valve pulsing sync with the ticking sound, there you go

http://jackassofalltrades.com/ticker.html
It sounds more like an oil issue tbh but I'll try that at the weekemd and see what I get