UPDATE: I had my v-belt replaced with the result that the early morning squeaking noise only became worse.
However, the early morning "squeak-squeak-squeak" is clearly somehow related to the v-belt area or to the issues Hummertech mentioned above.
Please, I need someone to help me figure out what the problem is and how it could be fixed. We don't have any official HUMMER dealers in Germany so nobody really knows where to look or what to do to fix this.
However, I have a very competent garage that would be able to look into this, if they only knew where to start or what needs to be fixed.
Hummertechs briefing above wasn't really sufficient, since there are dozens of "brackets" or "pullies" under the hood. Could someone (or Hummertech) please give me a more detailled description of what needs to be done? Or maybe there really is a service bulletion about this issue (like Hummertech said above).
Thanks for your help.
