Swap plastic for aluminum. And forget about cracking, forever.
Here are your choices: you can wait for the plastic factory thermostat housing cover to break and cause major overheating. (Even with a new stock cover, it won't take long.) Or you can install a thoughtfully engineered all-aluminum thermostat housing cover from Active Autowerke and never experience this type of failure again. Sure sounds like a no-brainer to us.
Currently there is no factory upgraded part to this problem. This is an aluminum extruded part that has all of the openings machine properly to fit like factory; from the mounting bolt holes, the seating of the thermostat to the sealing opening for the ORANGE gasket. Forged to exact factory tolerances, everything fits and this unit is a true easy bolt-on especially suited for racing or load conditions like heavy traffic, where engine temp can rise rapidly. The housing is guaranteed never to break from overheating or over-tightening, and its CNC machined surface ensures a precise seat.
Unit comes complete with a new ORANGE sealing gasket; a new thermostat is recommended but not included. For hotter climates, a 71 degree thermostat is recommended over the 82 degree unit.