A friends 2000 Monte with a 3.4 v6 suddenly started running rough while blowing a lot of coolant vapor through the exhaust and the temp ran up. Fortunately he quit driving it and had it towed home. It will run but of course it blows out vapor. It appears that it has lost very little coolant. Before I start testing for a bad head gasket I wanted to know if there is any coolant connection or gasket that could allow coolant into the intake that could be causing this. Thanks if anyone has any idea on this.