I have a late 2007 E93 325i auto with the N53 engine.
A few months back I noticed a slightly irritating ticking noise which becomes more prominent on acceleration. I've not had any error codes or loss of performance, so I just put up with it.
Curiosity got the better of me so I started looking into it and came across this thread. There was a recommendation for the N52 engine to rev to 2500rpm for 3 minutes while stationery. Even though I have the N53 I thought I'd give it a go.
After about 2 and a half minutes there was a noticeable change in rev noise and the ticks went away! But disappointingly they returned a day later. I thought I'd try it again this evening and once again the ticking has stopped.
What's wrong with my car? I have the extended BMW warranty (UK), is this problem likely to be covered under warranty?
I'm reluctant to pay the extortionate diagnostic fee!