1994 Mercedes-Benz E420 Problems

RepairPal has identified the most common problems with the 1994 Mercedes-Benz E420 as reported by actual vehicle owners. We'll tell you what the problem is and what it'll take to fix it.

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28
Known Problems

Ports in the cylinder head related to the emissions air injection and EGR systems can clog; the cylinder head should be removed and the ports cleaned.

A faulty mass air flow (MAF) sensor can cause erratic/rough engine operation and fuel economy issues. Since this sensor measures the actual amount of air entering the motor, when it fails, the engine control module (ECM) takes the wrong information and delivers incorrect volumes of fuel to the cylinders.

The lower control arm bushings can wear and crack, resulting excessive movement at the control arm pivot point, leading to irregular and premature tire wear. Worn Ball joints can also cause similar tire wear symptoms. I some cases it may be necessary to replace the lower control arm, including bushings & ball joint to correct this concern.

Internal and External engine oil & coolant leaks can develop from the head gasket and/or timing cover gasket; these leaks should be repaired before the engine oil and coolant intermix which can result in severe engine damage.

One or more blend door vacuum actuators may fail resulting in the incorrect output temperature from the HVAC system. Failed actuators will require replacement to restore proper HVAC operation.

The electronic throttle assembly may suffer an electrical failure. It is often cheaper to send the valve to a service center for repair that to purchase a new part.

Leaks may develop from the differential cover and/or seals on high mileage or older vehicles. Our technicians recommend a complete reseal of the differential unit if these leaks are addressed.

A vibration felt through the center floor of the vehicle can be caused by cracked and/or shredded driveshaft flex discs, resulting in excessive driveshaft movement. If not repaired, damage to the driveshaft center support bearing, transmission, or differential can occur.

One or more of the following steering linkage components may wear prematurely;  tie rod ends, drag link, or idler arm. Our technicians remind us the wheel alignment should be checked and adjusted if any of these items are replaced.

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.

Due to wear, high usage vehicles can experience ignition lock and tumbler failures. The ignition lock cylinder will generally require replacement to correct this concern.

A coolant leak may develop form the Radiator due to degradation of its plastic components. Replacement of the failed radiator will be necessary.

As brake fluid becomes dirty over time, it can cause a failure of the anti-lock brake system (ABS) modulator assembly. Our technicians recommend a complete brake system flush every two years to help prevent this issue.

The brakes may begin to squeak at about the 50 percent wear point. This is due to the size and material used for the brake pads and rotors.  The brake rotor surfaces become uneven, causing a lip to form at the outer edge. This will generally require replacement of the rotors when the pads are worn (pad life varies depending on driving style and terrain).

Due to exposure to the sun, lenses for head lights may become opaque (cloudy or hazy). This reduces the effectiveness of the lights. Our technicians tell us plastic polishes can improve the clarity of the lenses, but replacement of the lamp housings is the only way to regain the full intensity of the lights.