Q: Car overheats. Replaced thermostat, overflow cap, heater core. car was blowing cold air, massive leak from heater core hoses.

Of course, be sure it is not just a temperature sender and/or gauge malfunction. If there is trapped air in the cooling passageways that can cause overheating. There are a few other common causes of overheating, namely a faulty thermostat (inapplicable in your case although be sure you used a genuine OEM thermostat), a plugged radiator, collapsed hoses, non functioning cooling fans, and a faulty water pump or drive belt. Certain engine faults, such as a leaking head gasket or poor engine running condition can also cause overheating. If you desire that this problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request an engine overheating diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.