I'm not familiar with the car but if it's tight like the V8s you're going to need a special tool - it's like an open sided socket, sort of a cross between a crow's foot and a socket. It's a special MB tool - about $35. Someone posted a picture of it once in a prior thread, with a part number. You might be able to find it with a search. It's 22 mm as I recall. Snap On also sells one but about the same price and probably special order either way. But I'm pretty much guessing here - there may be a better way to get at it.