I just thought I'd share my experience with start up rattle.

After picking up my motor last April I noticed when it had been stood for a few days upon start up it would rattle for a split second but only after when it was shut down last at full running temp for example if I start it up from cold move it around the drive the shut it off while still cold then leave it standing even a week later it wouldn't rattle on start up but it would rattle if I'd shut it off after a 40 mile drive then leave it 2 days, so after looking into it I had stumbled on to the threads about changing the tensioner, so went ahead and changed and there was no change still made the noise.

Another thing to note is my motor had a service about 3k before I bought it and by now it was about 7.5k and I had noticed the noise becoming more frequent so decided to carry out an oil change and while I was at it I dropped the inspection panel in the sump and it was as clean as a whistle, it had previously had 5w40 oil used so thats what I used again and this made it go back to making the noise less often.

So I went on the search again and stumbled across this Wiki post talking about the M62 start up rattle on the BMW and Land Rover that use the engine and how it was known and regarded as acceptable by the main dealers and that the rattle comes from the Vanos unit and not the chain and sure enough when I had a friend start my car from cold I listerned and the noise was coming from the right head at at the front where one of the the Vanos units is situated.

Check it out:

M62 Startup Rattle - fullfatrr.com Wiki

After reading this I decided to swap out my oil from 5w40 to a good quality Fuchs GT1 5w30 so the oil is thinner at higher temps so when I shut it off after a long run the oil was thinner than before with the 5w40 and guess what I've had no rattle for 2 months.

So before writing off your guides or tensioner start with the basics check what oil your garage is putting in your motor and make sure its a good quality