Anybody how much a headgasket job on the ML would be at a indi. I have sludge in the expansion tank, but not in oil and the car drives fine. Recently had the inlet mainfold replaced at the indi so not looking for another big bill just yet. Could it be anything other than headgasket. as it was fine before the inlet job, could anything have been disturbed or the fluid contaminated. I can't get it over for them to have a look at until the weekend.