2001 Focus Cylinder Head Issue
 

I've recently replaced the cylinder head gasket on my girlfriends car, and have used the haynes manual and followed everything down to a T ... as the book says... got the last bolt on filled the fluids... checked everything 3 times ... then cranked it up.. slightly bogged down... then picked up .. high revved... then almost normal with a bit more noise possibly from one bolt breaking when removing the catalytic converter... major issue i have so far.. the passenger side is leaking from where the gasket was put in.. and a friend of mine said i should have used a silicone sealant before putting the gasket on... any idea of a fix or should i tear it down once more any help would be greatly appreciated on this issue