The oil pan gasket on a Mercedes seals the mating surfaces between the oil pan and the bottom of the engine block. Vehicles, such as the C Class Mercedes, use a one-piece rubber oil pan gasket that rests inside a lip on the oil pan. To remove and replace the oil pan gasket, you must remove the oil pan itself. This makes the job more labour-intensive and requires some automotive know how to ensure the seal does not leak once it's replaced.
Place a drain pan under the drain plug on the oil pan. Open the drain plug with a socket and ratchet then drain the engine oil into the drain pan. Once the oil drains, replace the drain plug into the oil pan and tighten it with the socket.
Remove the bolts that secure the oil pan to the bottom of the engine block. Depending on the model of Mercedes you have, there could be as many as 18 to 24 bolts holding the pan to the engine.
Pull down on the oil pan to break the seal between the pan and the engine. If necessary, wedge a thin metal scraper between the pan and the engine block to break the seal.
Slide the pan forward and manoeuvre it around the oil pickup tube inside the oil pan mounted to the engine block.
Scrape the old gasket off the mating surfaces of the oil pan and the engine block with a metal scraper and a towel. The cleaner you get the two surfaces, the better chances you have of limiting oil leaks.
Place a bead of RTV gasket sealer onto the mating surface of the oil pan and allow it to cure for 20 minutes. Place the oil pan gasket on top of the RTV sealer then apply a second bead of RTV sealer on top of the gasket. Allow that bead to cure for 20 minutes before proceeding.
Slide the oil pan into place. Be careful not to touch the RTV sealer on any part of the engine while you manoeuvre the pan into place. Once in place, push the pan directly upward onto the engine and thread a bolt into each corner of the oil pan with your fingers. Only thumb-tighten the bolts.
Thread the remaining bolts into the oil pan using a criss-cross pattern. Only thumb-tighten the bolts. Allow the RTV sealer to cure for another 30 minutes before continuing.
Tighten the bolts with a socket and ratchet in a criss-cross pattern.
Open the oil fill cap on the engine valve cover and place a funnel into the hole. Pour 4 quarts of engine oil into the engine. Remove the funnel and close the cap.