Hi everyone. I'm a new X5 owner and i have the self leveling suspension. I'm not sure if this is normal or not, but every once in a while i could hear my rear air bags working. It makes a vibrating rattling noise. I didn't know where it was coming from at first until i tried the self leveler. It only seems to make noise or rattles when I raise it or it raises itself. The bags seem to work fine, it goes up and down. I'm just trying to figure out if the rattle/vibrating noise is normal.

Also I have a Black 03 4.4 with 60k. Any recommend major service i should do?

thanks in advance