Sometimes it's not that easy to tell just where the leak is coming from; however, I beleive I've had the valves themselves leak on each of my three OM606 motors ... all at around 200,000 miles. The leaks in my estimation seemed to come out of the electrical connection but everything was wet so it could have been a crack. When I replaced the valves on each car I also replaced all the plastic lines and o-rings which has gotten me at least 50,000 miles without any fuel leaks on each car. I'm not sure of the exact tool size to remove the bolts .... but it makes sense to get a good set because you can find those fasteners in odd locations and differening sizes around the vehicle. Good Luck.