One problem related to brake disc pads has been reported for the 1998 Mercedes Benz ML320. The most recently reported issues are listed below.
My mercedes truck has burned through 4 or 5 sets of brake pads in the front and two sets for the rear within 63300 miles of driving, our driving is mostly on the freeway. I called Mercedes Benz they told me to take it to the dealer, which I already did. My dealer tells me that this is a universal problem with the ml 320 and ml 430 trucks, they are heavy vehicles and the components of the brake pads are soft and so are the brake rotors. It is the design of these components and the weight of the vehicle that contributes to a high burning rate of these brakes. This was told to me by the dealer as well as another mercedes service center.