[san rensho]

Could be a cap, could be air in the cooling circuit, or if its an older car, the coolant tank could be cracked. Pull up the carpet in the trunk and see if there is coolant on the trunk floor. If there is, its the coolant tank. Look for leaks in the entire cooling system. That means getting under the car and checking all the hoses and radiators.

If there are no visible leaks, bleed the cooling system. If you don't know how to bleed the cooling system, look it up at the Pelican site or Pedro's Technolab site. Don't fool around with overheating in these cars. A brief overheating episode can lead to catastrophic engine failure.