It is not uncommon for the power steering rack to develop a fluid leak requiring replacement of the rack assembly. Loss of power steering fluid may also cause an abnormal noise and damage to the power steering pump.Google+
Car Problem Reports
Mercedes-Benz ML500 Steering Rack Prone to Leaks
Mercedes-Benz ML500 Problem
Average Mileage: 81,000 mi (50,000 mi - 118,000 mi)
Visitor, 2006 Mercedes-Benz ML500, 50,000 mi
Steering rake replaced with only 50,000 miles on it I'm original owner.
Visitor, 2006 Mercedes-Benz ML500, 87,000 mi
vehicle has lost 85-90 percent of hydraulic assisting power.
Visitor, 2003 Mercedes-Benz ML500, 118,000 mi
Lost power steering and have a loud noise. Looking for a repair shop still.
Visitor, 2003 Mercedes-Benz ML500, 75,000 mi
power steering leaks and noisy
rack is leaking
Not sure yet where the leak was found as my vehicle is STILL at the dealership! I have had to replace the power steering pump, reservoir, belt, pulleys, rack and pinion...so far! GEEZZZ!!!!
Visitor, 2004 Mercedes-Benz ML500, 75,000 mi
power steering fluid leaking