My sisters '06 550 is making a knocking noise in "D" drive when idling. she has 45k mi. still under warranty. She always puts premium gas. Any thoughts on what it might be? Has anyone else come across this problem?

 

Hi, I have a 2008 528i had a ticking noise for 22000 miles ontill BMW finally replaced the cylinder head. Repair before included removing air from the oil?? good luck