1997 Mercedes-Benz E420 Problems

RepairPal has identified the most common problems with the 1997 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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Known Problems

Failed spark plug wires and/or ignition coils can cause intermittent misfires (rough running); the Check Engine Light may also illuminate. Diagnoses of the ignition system will be necessary to determine which components are at fault.

The mass air flow sensor can fail, resulting in poor fuel economy and Check Engine Light illumination.

The evaporator temperature sensor can fail, causing the AC compressor not to cycle. If the AC compressor does not turn on, the AC system will not blow cold air. If the compressor is stuck on, the air will be very cold at first, before warming up.

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.

A malfunctioning HVAC blower motor regulator can cause the blower motor to operate below the requested speed or not at all. Updated regulators are available; the blower motor and cover need to be replaced at the same time to upgrade the system.

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.

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.

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).

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.