by cedwards » Sat Apr 18, 2009 7:01 pm
Try idiling with radiator cap off, see if any bubbles come through from engine, that generally means blown gasket or cracked head forcing gas into water jacket. Note you may only see small leaks when engine is driving and under load so not always when idiling.
Is the oil clear or is there milkiness?
Any oil floating around in top or radiator?
When up to temp with the radiator cap on you'd expect for it to be filling the overflow that the radiator hoses are as hard as a rock! ie under haeps of pressure. Otherwise could just be a faulty radiator cap (may pay to test drive with another cap off another car if compatible)
Generally will only overheat when radiator starts running out of water, unless thermostat or pump faulty.