Refill the radiator with distilled water, then with the cap off, start it and see if it bubbles over. If not, purchase a lever-vent cap (if you don't already have one) and install it. Drive around till you reach operating temp, then turn the heater on full blast. If it's hot then cool, you got a leaking head gasket.
Last edited by wildbill; 08-04-2011 at 03:42 PM.