So I drove the car to st pete from tampa,got to where i was going,parked and at an idle it was knocking from the back of the motor and putting out a little bit of white smoke from the rear,checked in the next morning and there was no smoking and no knocking,drove it for a mile and I got smoking and knocking parked and idling.Got it home and it still did it and smoked alot more than before and still knocking the same.When i cut the car off and turn it back on it doesnt knock but still smokes.Doesnt overheat and drives fine,and doesnt knock or smoke when youre driving.Im hoping I just have a blown head gasket and not a cracked head/block.any ideas?