Having recently suffered a similar failure I would like to reiterate the previous findings and advice from Diggerman and others...... The plastic tee pieces fitted to the water cooling systems on the Sigma engines are prone to distortion and then fracturing. I have replaced my larger (failed) tee with another plastic item until the brass replacements arrive (hopefully tomorrow). Like myself, newer (and some existing) owners may not be aware of this issue. Not sure how long the tee pieces take to deteriorate, my car is 6 years old. So far, the re-filling of the system with water has been straight forward with no complications. 2010 Roadsport 125