The relay which turns the airmatic suspension pump on may fail causing the pump to run continuously. This can result in failure of the pump motor or a dead battery as the pump motor will continue to run after the car is turned off. Also, Worn airmatic pump mount bushings can causes noises in the front axle while driving on bumpy roads or a buzzing noise while the pump is running.
Airmatic Pump Motor May Fail Due to Sticking Relay on Mercedes-Benz CLS55 AMG
Average mileage: 72,000 (72,000–72,000)
1 model year affected: 2006
2 people reported this problem
some motor is running behind the dash when the car is off. it eventually stops but not sure what it is.