1990 Mercedes-Benz 300SE Problems

RepairPal has identified the most common problems with the 1990 Mercedes-Benz 300SE 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

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.

Other than a defective motor, a bad switch or blower motor resistor assembly can cause an inoperative heater blower motor.

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 pool where the ignition wire resistor connects to the spark plug. The resistor can fail and the spark plug may not fire because of a short circuit through the oil.

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.

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 required to restore proper AC operation.

Early-style stainless steel fuel injectors may develop fuel leaks. On high mileage vehicles, the fuel distributor may leak.

The expansion valve can get stuck and is difficult to replace.

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 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 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.

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

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.

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.

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