broken down porsche 944?
 

My customers bought a Porsche 944 last night and attempted to drive it home at fair 30miles. My customers started to hear tapping sounds coming from the engine when engaged in gear generally in the higher revs. It got louder and louder and my customers was slowing to compensate, and then a huge cloud of thick white smoke came from the exhaust and the car lights begun to flicker and the car was slowing until it just stopped. The engine was steaming for a while Volvo Vocom 88890300.

Anyway, my customers left it there overnight and got recovery to my customers home this morning. RAC said it was a head gasket? but my customers is not so convinced about the tapping/clunking sound. The coolent is empty and when the white cloud emerged the water temp gauge went crazy.

What is happening to my customers poor new porsche? and is it something my customers can fix myself?