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.

Determined that the bolts on the thermostat housing cover require "external TORX" socket for tightening. Found a nice six-socket set manufactured by Lisle at Sears ($20). Size required for this job was E10.

you mentioned leak, which part of the thermostat?

Was leaking where the top of the thermostat housing (part containing the temp sensor) joins with the body of the thermostat housing.