Previa Expansion Tank

[mrman30]

Hi everyone i have a 1996 petrol previa the water was bubbling back through the expansion tank but was not overheating so i had a block test done to see if the head gasket was going but it wasnt so anyway this morning i was driving along when i heard this all mighty bang so i pulled over and opened the bonnet only to find that my expansion tank had completly burst an split in halve please could anybody tell me waht may have caused this and also how to fix it many thanks

[Jamesbelfast]

A failed pressure release of the coolant cap. An air lock. Blown head gasket. Jammed thermostat - take your pick.:)

[bothwell_buyer]

for what its worth, I had to get my plastic expansion tank changed as it was split. Then we found that the head had cracked.... bit of a chicken and egg as to which happened first!!