On my 91 560SEL I have 2 head gasket leaks located at the rear corner on both sides. Very slight, not enough to cause alarming loss of oil ( I add about a quart every 1500 miles), but has had the problem for more than 2 years now. I have not thought of doing anything about it yet, except to monitor it via drips on the floor and loss of oil. I probably see one drip the size smaller than a dime each morning. I detected the exact location of the leaks by cleaning the engine with engine degreaser from under the car, wash it off, let it dry and drive it for about 50 miles, then went under the car. The source of the leaks could easily detected with all the sorrounding areas still dry..