Mercedes-Benz S500 Problems

RepairPal has identified the most common problems with the Mercedes-Benz S500 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

The active body control system can leak fluid from numerous areas, including the tandem pump, hydraulic lines, struts, and/or seals. If it is not repaired, the vehicle ride height could drop too low and cause damage to the undercarriage.

The Mercedes Benz S500 may have engine oil seeping or leaking from the back of the cylinder heads. This is commonly misdiagnosed as leaking valve covers.

On the back of the cylinder heads there are three, in total, plastic expansion plugs that plug access ports to the camshafts. These plugs are well known for seeping oil, and leaking if left unattended. The oil will run down the back of the engine and eventually make it to the ground. 

Replacement of these three plastic plugs is extremely simple, and should be done as regular maintenance. The recommended interval for replacement is every 60,000 miles.

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

The relay which turns the airmatic suspension pump on may fail causing the pump to run continuously. This can result in failure of the pump motor or a dead battery as the pump motor will continue to run after the car is turned off. Also, Worn airmatic pump mount bushings can causes noises in the front axle while driving on bumpy roads or a buzzing noise while the pump is running.

The ESP and BAS warning lights may illuminate due to a failed brake light switch. Replacement of the failed switch should correct this concern.

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.

The engine wiring can degrade because the insulating material falls off leaving the bare wire exposed. This can cause many problems depending on which wires are exposed and what they touch.

The door for the vanity mirror (or the frame for the door) can break; due to a redesign, the mirror "cassette" will need replacement.

The crankshaft position sensor may fail. Symptoms of this are: The engine will crank—but not start—especially when the engine is warm. The car may start again if it is left to cool off, but it may run roughly or have poor performance.

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

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.

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.

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 refrigerant leak may develop from one or more of the following AC components: AC compressor, hose manifold for the compressor, or the evaporator core. The loss of refrigerant can cause poor AC performance. Our technicians tell us that proper leak diagnoses should be performed in order to determine the cause of any refrigerant loss.

CD changers, command units, voice control units, PSE units, and Tele Aid units are prone to failure, especially in early models.