Why is my car overheating

If you lose sufficient radiator coolant any water cooled engine will overheat as will yours. You do not need to lose very much coolant for an overheating condition to occur.

If you allow the engine to run in an overheated condition you WILL cause very expensive engine damage many times what it will cost you to have a new water pump and new WP gasket fitted.

When cold fill the radiator with water and leave the cap off. Make sure that you have all the air out.
Start the car and watch the radiator, you are looking for air bubbles coming out of the radiator. If you have a steady stream of bubbles appearing you have a blown head gasket.

With what you describe sounds like the hot water is just heating up but not circulating and cooling correctly. Possible causes, airlock, faulty water pump, check fan belt tension, not broken etc, blockage in engine water way or collapsed hose. Are you losing water at all? Head gasket?

Usually a bad water pump will cause the engine to run hot with or without the ac being involved. The most common cause of overheating with the ac on is not enough air flow thru the radiator.

If the overheating is only occasional, it sounds like the radiator still has some blockage that moves around and plugs up again. Try flushing it backwards again. If it continues, consider a new radiator. A radiator is cheaper than head gasket work, which may happen if it keeps overheating.

sounds to me like you either... (A)- have a blown headgasket... (B)-have a warped head.. have the exhaust fumes checked in your coolant overflow tank by a local mechanic

Overheating can seriously damage a car's engine if left unchecked. Although overheating simply means that a car's engine temperature exceeds normal operating temperatures, the causes of overheating are varied. What follows is a brief list of some of the most common causes of engine overheating.

Faulty Radiator
1. A car that overheats will often have a faulty radiator. A radiator is responsible for cooling hot engine coolant that picks up heat from inside a car's running engine. A radiator "radiates" the heat from engine coolant out into the outside air. A faulty radiator loses its "radiating" effects and allows engine coolant to become overheated, thus rendering it ineffective at adequately cooling and engine.
Faulty Water Pump
2. A faulty or malfunctioning water pump prevents adequate engine coolant flow and can cause a car to overheat. A water pump serves to pressurize and propel engine coolant throughout a car's engine and radiator to increase the heat-reducing capabilities of engine coolant. A faulty water pump loses its ability to adequately pump and propel engine coolant, and can cause a car to overheat.
Coolant System Leaks
3. A leaky engine coolant system reduces the level of circulating engine coolant, which increases engine temperature and leads to engine overheating. Radiators, water pumps, and coolant system hoses and seals--all of these coolant system parts can develop leaks, which can result in low coolant levels and engine overheating.
Faulty Thermostat
4. A car thermostat regulates the flow of engine coolant. A thermostat is a heat-sensitive valve that opens when a car engine reaches a set operating temperature and closes when a car engine is cold and warming up. If a thermostat gets stuck in the closed position, coolant will be prevented from reaching the engine, which will quickly lead to engine overheating and potential engine damage.
Low Engine Oil Level
5. Engine oil, in addition to lubricating an engine's internal parts, helps to keep engine operating temperatures reduced by eliminating friction within the engine. If engine oil levels are low, friction and heat build up inside an engine, a condition that causes increased engine operating temperatures and can lead to engine overheating.

Have you changed the water pump ?

It sounds like water pump may be your problem. It circulates a 50/50 mixture of glycol (or some form of) and water through the engine block and cylinder head and back through the radiator. In the radiator the mixture is cooled when air passes over the fins of the radiator. This is accomplished by driving or a mechanical/electrical fan when stationary. The water pump also circulates the mixture through the heater core giving the car heat. If the water pump is not circulating the water back to the radiator to cool, it will overheat. More heat is caused by the engine when driving (much less heat when idling), hence the overheating while driving.
I hope this helps and good luck!

Sounds like to me it would be your water pump before a heater core. When the water pump goes out, it stops pumping the coolant through the system which is what would cause it to still overheat even with the thermostat out. Change the water pump and you should be good. Let me know if you have any other questions. Thanks for using FixYa!