The electrical connector at the automatic transmission may leak fluid into the wiring harness. If not repaired, the oil will migrate through the wiring harness and damage the transmission control module. At that point, a new harness and control module may be necessary to correct this problem.
Problems for specific Mercedes-Benz E320 years:
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Most reported Mercedes-Benz E320 problems
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.
Rear air springs (bellows) may develop leaks, which causes the air pump to run more often to maintain ride height. Our technicians recommend that leaking air springs be replaced.
A coolant leak may develop form the Radiator due to degradation of its plastic components. Replacement of the failed radiator will be necessary.
A coolant leak may develop from the water pump. When replacing the water pump, the drive belt tensioner should be inspected and most likely replaced as well.
The emissions air injection pump can seize, causing a loud squealing noise followed by smoke from the drive belt. If the engine is not turned off, the belt will break, turning on the alternator/battery warning light.
Motor mounts commonly fail, causing engine vibrations to be transferred to the body. Failed motor mounts should be replaced in order to prevent damage to the transmission mount.
When the engine is running, but the vehicle is not moving, a rattle heard from beneath the vehicle could indicate that one of the exhaust catalytic converters has failed. The substrate (the internal part of the catalyst that reduces emissions) can loosen and bounce around inside the canister section of the converter—the defective unit will need to be replaced. If this problem is ignored, the substrate can break down and reduce to a size that plugs the outlet pipe, which will cause a sudden loss in power.
A vibration felt through the center floor of the vehicle can be caused by driveshaft flex discs, which crack and shred, causing excessive driveshaft movement. Not repairing these can cause damage to the driveshaft center support bearing, or, in the worst case scenario, damage to the transmission or differential.
The early versions of the central gateway module (which allows different systems to communicate with each other) have software problems.
Lack of audio or cell phone functionality may be related to the failure of the audio gateway module.
Many software updates are available for the different computer systems, but if the vehicle is out of warranty, it may cost money to receive the updates (unless it is a recall). Some updates may be dealer-only, but a well-equipped independent shop can usually provide updates as well.
Fuel leaks, erratic or rough engine operation, and fuel economy issues can be caused by the failure of a fuel system component called the EHA (electro-hydraulic actuator) valve.