For about the past month ive been having problems when i start the car, the car seems like it wants to die and has a rumble taht shakes the whole car and the rpm's lower. I also have been losing alot of coolant, but there is no puddle under the car. It seems that its dissappearing somewhere in the engine? Are these the signs of that the head gasket is starting to go? And if so how can i chcek for sure?