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1990 Mercedes-Benz 420SEL Problems

Find the most common issues based on 1990 Mercedes-Benz 420SEL owner complaints.
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Most Common 1990 Mercedes-Benz 420SEL Problems

Other than a defective motor, a bad switch or blower motor resistor assembly can cause an inoperative heater blower motor.
It is not uncommon for the idle air compensator to get stuck in one position, resulting in the engine idle speed (rpm) being too high or too low. Replacement of the failed compensator may be nece...
A refrigerant leak may develop from one or more of the AC hoses. Proper leak detection procedures should be followed if refrigerant loss in encountered. Replacement of any leaking hoses will we r...
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2 Known 1990 Mercedes-Benz 420SEL Brakes Problems

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 t...
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 hel...

4 Known 1990 Mercedes-Benz 420SEL Drive Train Problems

High mileage vehicles may develop a transmission fluid leak from one or more of the oil seals.
The bushings for the shifter lever wear out to the point where they break and fall out. This causes excessive movement (loose feel) in the shifter lever and a clanging-type noise when changing gears.
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...

2 Known 1990 Mercedes-Benz 420SEL Electrical & Lights Problems

The fuel pump and/or fuel pump relay can fail, causing the car to crank over but not start. Proper diagnoses will be necessary to confirm if the pump or relay is at fault.
The instrument cluster, along with the turn signal and wiper combination switch, can fail.

3 Known 1990 Mercedes-Benz 420SEL Engine Problems

It is not uncommon for the idle air compensator to get stuck in one position, resulting in the engine idle speed (rpm) being too high or too low. Replacement of the failed compensator may be nece...
The timing chain and timing chain guides wear; they should be replaced every 100,000 miles.
The rubber boot connecting the throttle body to the intake manifold tends to crack. This can cause hard starting, rough or erratic idle, and engine performance problems.

2 Known 1990 Mercedes-Benz 420SEL Exhaust & Emissions Problems

A rough running motor or lack of power can be caused by a failed distributor cap or rotor, ignition wires (or their resistors), or valve cover gasket leaks. If the valve cover gasket leaks, oil can...
Valve stem seals may wear and cause the engine to burn oil. this can contaminate the catalytic converter and cause it to fail.

5 Known 1990 Mercedes-Benz 420SEL Heating & Air Conditioning Problems

Other than a defective motor, a bad switch or blower motor resistor assembly can cause an inoperative heater blower motor.
A refrigerant leak may develop from one or more of the AC hoses. Proper leak detection procedures should be followed if refrigerant loss in encountered. Replacement of any leaking hoses will we r...
The expansion valve can get stuck and is difficult to replace.

0 Known 1990 Mercedes-Benz 420SEL Maintenance Problems

2 Known 1990 Mercedes-Benz 420SEL Miscellaneous Problems

One or more door windows may stop working due to a failed window regulator. Replacement of the failed regulator will be necessary to correct this concern.
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.

4 Known 1990 Mercedes-Benz 420SEL Suspension & Steering Problems

Power steering hoses and components can develop leaks.
On high mileage vehicles, rear spring wear may cause the rear end to sag.
The tie rod ends, idler arm, and/or drag link components of the steering linkage may wear prematurely. Please keep in mind the wheel alignment should be checked and adjusted when any of these i...

24
Known 1990 Mercedes-Benz 420SEL Problems & Complaints

A rough running motor or lack of power can be caused by a failed distributor cap or rotor, ignition wires (or their resistors), or valve cover gasket leaks. If the valve cover gasket leaks, oil can...
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 climate control system can fail or perform erratically due to internal problems with the climate control button electrical contacts. Replacement of the climate control assembly is commonly re...
Other than a defective motor, a bad switch or blower motor resistor assembly can cause an inoperative heater blower motor.
One or more door windows may stop working due to a failed window regulator. Replacement of the failed regulator will be necessary to correct this concern.
A worn steering dampening shock can cause a fluid leak at the front of the vehicle. If a leak is noted from the dampening shock, our technicians tell us that it should be replaced.
The bushings for the shifter lever wear out to the point where they break and fall out. This causes excessive movement (loose feel) in the shifter lever and a clanging-type noise when changing gears.
High mileage vehicles may develop a transmission fluid leak from one or more of the oil seals.
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.
The tie rod ends, idler arm, and/or drag link components of the steering linkage may wear prematurely. Please keep in mind the wheel alignment should be checked and adjusted when any of these i...
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 t...
Leaks may develop from the differential seals and/or cover on older or high mileage vehicles. Our technicians recommend a complete reseal of the differential unit when 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...
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 hel...
A refrigerant leak may develop from one or more of the AC hoses. Proper leak detection procedures should be followed if refrigerant loss in encountered. Replacement of any leaking hoses will we r...
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