Ok so my mustang was overheating. Naturally I check the coolant, added coolant. Checked the thermostat, replaced with a lower opening temperature. Still overheating. Heats up faster with a/c on then blows hot air. White smoke blowing through vents temporary. Water pump went out. replace water pump. still overheating. Took it to Midas, they say pressure shot up as soon as they turned it on. Midas says either blown head gasket or cracked head. Oil on dupstick doesn't look any different. Any thoughts?