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Mercedes-Benz 300SE Problems

RepairPal has identified the most common problems with the Mercedes-Benz 300SE based on complaints from 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

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.

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.

Due to age and sun exposure, the interior wood trim cracks and the finish gets a cloudy haze. Replacement if the trim would be the most common solution to the problem.

Instrument cluster lenses break easily.

Glove box hinges, the center console armrest, and the cup holders break.

Problems with the pneumatic system can cause closing assist and door lock issues.

A cracked or broken heater core outlet housing can cause a coolant leak near the bulkhead (firewall). Our technicians remind us that coolant leaks should be repaired in order to avoid overheating the engine due to coolant loss.

Some models have tandem hydraulic pumps—one section for power steering and the other for suspension adjustment. These pumps are prone to leakage from either section.

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.

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 head lamp wipers are easily damaged, especially by automatic car washes.

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 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 required to correct this problem.

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