First off, I want to thank Gilly, MB Doc and everyone else who contributes here. There is wealth of information to be found. I went back and forth on whether to by and ML or an RX300 for my wife. I was a BMW mechanic for nearly 20 years and worked on many Porches and MBZ's too, but had heard a lot of negative stuff about the ML's. The info available here and the exceptionaly clean ML I found swayed me over to the purchase.

We now have a very clean '99 ML320 with only 39K on the clock. We've had it since December 26 and so far so good. (Dealer Starmark Purchase)

It just developed an odd "moaning" noise last night. The sound is very intermittent and lasts only about 20 seconds. It is not cyclic, or speed related. Downshifting, speeding up or slowing down do not effect it. It is hard to pinpoint because it lasts such a short time. It sounds as if it is either coming out of the HVAC area around the passenger side, or in the engine compartment in the area of the Aux coolant pump. It's actually emminating more in the area directly below the windshield on the passenger side. I am not yet familiar with the ML's HVAC system, but it sounds a lot like a lazy vacuum motor.

In any case, this started right after some recent work by the Dealer and myself:

The Dealer did a transmission fluid-filter service, both F/R diff oil service, transfer case oil service and the updated fuel filter with a new pump and fuel level sensor. They also installed the updated sunroof insulation panels.

Later the same day after bringing it home, I installed new spark plugs, a new air filter and a new cabin air filter. I installed the air filter with the short step toward the front of the vehicle so it doesn't block the intake snorkel and the cabin air filter as it came out with the foam edge-wrap toward the passenger door.

Any ideas?

Many thanks,
Toad