Overheating first thing noticed was the over heating. cheaked for coolent leval and noticed it was low. added antifreeze, but keeped losing coolant. found leak in radiator/cracked radiator. changed and still losing cooolant.no water in oil, no water on ground. found water leak on rear of engine. leaking intake manifold gasket. changed gasket, did tune up, replaced thermostat, still over heating. changed water pump, still over heating, help please

Temperature Warning Light is on Inspection Service How this system works: With the exception of older, air-cooled vehicles, cars rely on a liquid called coolant (or antifreeze) to keep the engine at an optimal temperature. Coolant is a mixture of water and ethylene glycol, and it circulates around the engine block and absorbs excess heat, which keeps the engine from overheating. The coolant converts that heat to air in the radiator, and then the air is emitted, at which time the coolant is ready to absorb more heat. Without coolant, the engine would quickly ruin itself with its own heat production. Common reasons for this to happen:

• Coolant is low or weak: The most common culprit when an engine overheats is low or weak coolant. If your car doesn't have enough coolant, then it can't absorb enough heat. While your car will naturally lose small amounts of coolant over the years, a leak is the most likely cause of low coolant levels.The proper ratio of coolant to water can also get distorted, resulting in a problem. Too little or even too much antifreeze can dramatically lower the boiling point of the coolant. A proper ratio of antifreeze to water is 50/50 to 60/40, depending on the vehicle.
• Broken radiator fan shroud: The radiator fan shroud directs the airflow across the radiator so the air can absorb the coolant's heat. When the fan shroud breaks or becomes dislodged, air fails to enter the radiator, and the coolant will no longer have a place to direct the transfer of heat.
• Broken or missing air dam: Along with the shroud, some vehicles have an air dam (or deflector) underneath the vehicle. If this is broken or missing then the air can pass underneath the vehicle but not also through the radiator, which will cause overheating. These air dams are essential in newer vehicles, as they force the air through the fan shroud.
• Faulty coolant temperature sensor: The temperature sensor takes constant readings of the coolant temperature and sends that information to the engine control unit. Based on the temperature of the coolant, the engine control unit adjusts the ignition timing, the fuel injector pulse, and the operation of the electric cooling fan.
• Bad water pump: The water pump is responsible for keeping the coolant cycling throughout the engine. After the coolant transfers its heat energy to the air, the water pump recirculates it around the engine so that it can absorb more heat. The most common water pump problems are a leaking pump, bad bearings, or an impeller that has rotted away due to a low coolant ratio.
• Stuck thermostat: The thermostat acts as a dam for the coolant. When the engine first turns on, and it is still cold, the thermostat keeps the coolant from circulating, which allows the engine to warm up as quickly as possible. Once the engine has reached its operating temperature, the thermostat opens and allows the coolant to circulate. A stuck thermometer may stay permanently sealed and therefore keep the coolant from reaching the engine block.
The thermostat may also stick open. This will not usually result in overheating, but it will waste gas.

• Broken engine cooling fan: The engine has a cooling fan that is deployed when the coolant needs some extra help. When the coolant temperature sensor notices that the coolant temperature is getting too high, the engine control unit (on newer vehicles) will initiate the cooling fan to reduce the temperature.
• Broken thermostatic fan clutch: Older vehicles use a thermostatic fan clutch to engage the engine cooling fan, which is mounted to the fan blades. The fan clutch uses a bi-metallic spring that tightens when the temperature increases. This acts as a "high speed" option for the fan, and when engaged, it draws more air across the radiator.
• Blown head gasket: The head gaskets sit between the engine block and the cylinder heads, and keep coolant from entering the engine's oil and combustion chamber. When a gasket blows and coolant seeps in, the issue is not only that the engine will overheat, but also that damage may be done to the catalytic converter and oxygen sensors due to contamination from the coolant. What to expect: A top-rated mobile mechanic will come to your home or office to determine the cause of the temperature warning light turning on and the source of the overheating, and will then provide a detailed inspection report that includes the scope and cost of the necessary repairs. How important is this service? An overheating engine is extremely dangerous. It is not safe to drive a vehicle with an overheating engine, or you may ruin the engine completely and put yourself at risk. As soon as you notice the light come on, pull over. If there is no place to safely pull over, turn off your radio and other electrical units, and turn your heat on high (this will funnel some of the hot engine air into the cabin). As soon as you can safely pull over, do so, and then book one of our mechanics to perform an inspection.
  

is there still coolant in the system? you should find out why it went low in the first place

How are you adding coolant, why, and how is the engine overheating ?
It could be that you have a blown head gasket and the engine is burning the coolant out the exhaust.

check the level of antifreeze or thermostate is bad

you can leave the cap off the same way to check to is if it is circulateing,is your water pump leaking? if your loseing coolent.

If you've added two gallons of antifreeze, you need to find out where it's going. Make sure the antifreeze you are adding is diluted with water in a 50/50 solution. Pure antifreeze has little freeze protection and boils quickly. If there is no visible leak, check your oil for coolant contamination. Fill the radiator and leave the radiator cap off. Put the heater controls on hottest setting, but do not turn the heater on. Start the engine and watch the coolant. If the coolant level drops, add more to full. If the coolant is flowing thru the radiator when you first start the engine, the thermostat is stuck open and needs to be replaced. If the water is not flowing, then keep an eye on it and wait for the thermostat to open. Add antifreeze to keep the radiator full. Look for air bubbles or lots of foaming in the coolant. That would indicate a blown head gasket and the reason you are losing antifreeze. If there's no bubbles, and the coolant level stays full, put the radiator cap back on and see if the heater is working better.

overheating is most likely a bad thermostat, but the coolant loss is a second big concern. Does the exhaust look like steam? You could have a cracked block and the coolant is leaking into the engine. Also check the oil for contamination.

Check the sensor which controls the cooling fans that cools the radiator it prevents the engine from over heating and allows the temp gauge to stay at normal range.recently had problems with my 2003 impala overheating it was the sensor had the thermostat replace as well.

Be sure to keep an eye on your coolant level. If there's a leak, then it'll just get low again and return with no heat. There'll also be a chance on overheating your car if it's low on coolant.

Make sure if you're adding water, that it's DISTILLED water. It's free from impurities and will be much better for your system.

It's actually recommended to use 50/50 diution of antifreeze and distilled water. You can buy this already pre-diluted, which is easiest. Or you can buy the full mixture of antifreeze yourself and mix it 50/50 with the water.

Your thermostat will not affect the heat in your car. This is controlled by the heater core which is pulled from coolant from the engine where the coolant will be the hottest. Your thermostat opens and allows the coolant from the engine to circulate into the radiator and the coolant from the radiator flow into the engine. A thermostat is cheap and easy to replace. The sensor should be a fairly inexpensive and easy replacement as well. I would change out the sensor first because bad thermostat would create an overheating problem.