Engine rattle help
 

If i leave the X for a few days without starting it, on first start up the engine has quite a loud rattle, knocking sound, it just sounds as though it takes a few seconds for the oil to get to the top of the engine and then it goes quite is this something i should be bothered about or not.
The car is a 03 4.6is 32000 miles
Thanks Karl

It may be the belt tensioner. However many BMWs have a rough cold start so it's probably not a problem. My X3 did this awhile, the belt tension was replaced, and the sound came back. Not bothering to fix it.

Mine made a cold startup noise too, I swore it was a lifter or worse. BMW spent a week diagnosing and replacing belt tensioner and chain tensioner. Turns out, it was bubbles on the bottom of the belt that caused the noise as the belt came around and struck the tensioner. Search other threads for possible solutions. Good luck

Thanks for the replys
I think i might of found the problem i had an oil change a few weeks ago and the garage did not use a genuine bmw oil filter and used some comma 5-30 oil.
I went to bmw today and got a genuine bmw filter and the oil they recomended is castrol edge 0-30 so the oil has been changed again now, i will see how it goes but hopefully it should be ok now with the correct oil in it.
I will post an update in a few days to see if the problem is sorted

Mine does the same thing once in a while. There is a thread some where I can't find it right now, but it stats from Bmw that it is very normal. The V8 does this don't know about the I6....