My wife's 07 Sienna LE just blew a head gasket and I'm really miffed and puzzled as to why it could happen. There's only 90K miles on the SIenna, it has never overheated, come close to overheating, and the coolant is still perfect. To make it more weird it did it 30 seconds after a cold start up pulling out of the drive way. Have there been issues with this generation sienna blowing head gaskets?