IIRC, it�s the two M6 bolts that hold the steel flange to the 1� hose to the head that Tom�s having problems with.  On a 1.9 thermo housing, there are (2) M8 bolts that pass through the housing and thread into the water pump and (4) M6 bolts that are always breaking. Two to hold the above flange on and two that hold the thermostat cover on. I Heli-coil those puppies whenever I had a housing in my hand. Stainless threads and a bit of anti-seize and they never break again.

Machine shop and Heli-coil. Do all four M6 holes.

Jim