Over heating car, and it doesnt stay on.

Coolant Issue:

Can you take a picture of the location that the coolant was coming through the firewall? From the information it sounds like the heater core. If that is the case the floor on the passenger side might be wet and the smell of maple syrup present inside the car.

Transmission Issue:

If it was low, there is a leak. Describe the location of the "clunking noise". Did it come from the transmission itself or the rear end? When did this noise happen? Were you driving? Parked? Shifting into a gear? Going in reverse?

No Start:

This can happen if the car shut itself down because of being too hot. Once it is cooled off, check the fluid level in the radiator, top it off before you try to restart the engine. Keep a close eye on the temperature gauge and keep filling the coolant until it stops bubbling and stays at a steady level. Make sure the heater is on high and full hot while doing this. If the car is leaking any coolant other than the fill neck, note this or take a good picture so we can chime in and help out.