have a oil leak somewhere in the rear of the motor just below the vavle cover
oil leak rear top motor on 1991 Mercedes-Benz 300E
Wash of the area with engine cleaner or Chemtool and see if you can identify if the leak is from the valve cover or an oil line in that vicinity. To pin point where oil is leaking from the engine may need to steam clean the engine first. Starting with a clean engine and then running the engine it may be easier to identify specific leaks. If the oil leak can not be identified, florescent dye may need to be added to the oil and the engine run for a while. After running the engine the dye used has florescence in the dye is visible under UV light and it helps pin points the source of the leak. Identify the color of the oil to differentiate whether the oil leak is steering fluid, brake fluid, or transmission fluid and try to identify the location of the fluid leak under the vehicle, ie front of engine compartment, rear of engine compartment , passenger or driver's side of vehicle..