One problem related to engine and engine cooling has been reported for the 1998 Mercedes Benz ML320. The most recently reported issues are listed below.
My battery was low and unknown to me the Ml320 for this year loses its transponder codes in the das security module when you try to start the vehicle with a low battery. This is evidentally the third key that has lost its programming on my vehicle due to low battery voltage. Cost so far is 499 for a key, weeks waiting for the key from germany, and 300 to program it once they recieve the key. Its a dealership only item so its very very costly. This is a known problem with mercades and checking the forums it seems that everyone that has 1998-2000 model mercades all lose their transponder codes between 129,000 and 132,000 miles no matter what. This is an obvious manufacturers defect and a known issue that should be paid for by mercades. I never had these issues with my two 2002 ml500's but I will never purchase another benz in my life.