I have a '97 E320 which has a slow leak at the thermostat housing. I want to torque the cover down a little as gasket was recently replaced with thermostat by my indie but I don't know what the tool required is. Heads of bolts resemble the end of a large TORX wrench but I don't think I have anything in my box that will work. Can someone tell me type and size of tool this requires. TIA.