Overheating problem Ford Focus lx 2.0L 2003: In overheating condition radiator fan not working and temperature gauge remain at middle position. Engine coolant temperature sensor is replaced but problem remained. When the ETC sensor is not connected fan works.

When water heats fast the temperature must be checked independently to eliminate possible electrical problems with the gauge or sender.

If the coolant really is getting too hot too fast a restricted coolant circulation should be suspected. Thermostat is the most likely cause of low or zero coolant circulation but other sorts of blockage are possible and it has been known for the water pump impeller to fall off the shaft or to break up., though these things are rare. I don't advocate suspecting this unless there really is no flow and this is best checked by disconnecting a heater hose.

A restricted air flow through the radiator or the cooling fan not working would probably cause overheating but that tends to take longer and be unremarkable in the speed of overheating.

It is possible for a leaking cylinder head gasket to pressurise the cooling system and displace coolant and disrupt the thermostat operation.

chek if the electric fan is turning on when the ac is turned on

Cars usually overheat when the thermostat is faulty, coolant level is low, or the water pump fails. If your cooling fan on the radiator does not kick on shortly after the engine reaches operating temperature, you may have a bad cooling fan, cooling fan relay, or cooling fan fuse. If your engine is overheating, start by checking the fluid level, and installing a new thermostat.

A blower motor resistor is the device that controls a car's cabin heating and air conditioning unit's fan speeds. This usually won't cause the engine to overheat, your A/C fan may not function or only function at one speed. Here is a Blower Motor Resistor from Autozone: http://www.autozone.com/autozone/parts/2003-Ford-Focus/A-C-Heater-Blower-Motor-Resistor/_/N-jk8uvZ91tag

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Your English is very good.

From what you have described, which is a rapid over heating of the radiator coolant fluid and therefore a hot engine condition, it would appear that the thermostat in the engine's cooling system is faulty.

If the thermostat is sticking in the closed or nearly closed position temporarily, there will be no flow or very little coolant flow between the engine and the radiator and the engine will overheat.

You have advised that after the engine is shut off , and radiator coolant fluid has cooled, you re-start the engine and drive the car without the overheating condition occurring again and the radiator coolant temperature is normal. This time there is no overheating because the thermostat is working normally.

You should have the thermostat replaced as soon as possible because allowing the engine to overheat can cause very expensive engine damage.

If you had a continuing overheating condition then I would suspect both the thermostat and the water pump. However as the overheating seems to be only temporary, and clears itself after you have shut down the engine and re-started it 10 minutes later (without further overheating arising) then I think you only have a faulty thermostat.

Please also check that the electric fans which draw air through the radiator are operating. These run on a temperature sensor and will switch on automatically once the radiator coolant fluid reaches a certain temperature and then switch off again when the fluid temperature reduces. You will hear them running once they start up. If these fans are not working the radiator coolant can quickly overheat in various driving and temperature conditions because there will be insufficient air flow through the radiator to cool the fluid. If the temperature sensor is faulty or has died, or if the electric motors running the fans are faulty, the fans will not operate.

I hope this helps.

When your temperature gauge reaches "H' it may too late to prevent a major breakdown. Knowing the symptoms of an overheated car and how they occur may be the difference between being inconvenienced and incapacitated.
Identification:---Other than a low oil level or low oil pressure light, there is not a more significant part of a car's instrumentation than a rising temperature gauge or a glowing "Hot" light. These lights are really the only confirmation a driver has that his car is really overheating. It is the identification of the symptoms of an overheating car that enable the motorist to avert a badly damaged engine. Overheating is always a traumatic event for a car's engine, which makes the early identification of the symptom an important addition to the informed motorist's tool kit.
Stuck Thermostat:--The car's thermostat is a valve that controls coolant flow from the engine block to the radiator. When the engine is cold the thermostat remains closed so that the coolant can reach operating temperature quicker and also provide heat to the passenger's compartment. The thermostat has a spring on it that moves depending on coolant temperature causing the thermostat to open. Sometimes the thermostat fails to open thus restricting coolant flow to the radiator where it would be cooled down. This condition is often the cause of overheating. The symptoms of this cause would be a rising temperature gauge and possibly the loss of heat inside the car.
Restricted Radiator:---A car's radiator will have thousands of gallons of coolant passing through in its lifetime. Along with the coolant comes particulate matter in the form of corrosion breaking loose from various parts of the car's cooling system. These contaminates collect in the tubes of the radiator reducing its efficiency. Extensive "plugging" in the radiator will cause the car to overheat. The symptom of this condition would be a rising temperature gauge which goes up when you accelerate.
Coolant Loss:--A car's cooling system is a closed loop system. You are not supposed to lose coolant. Sufficient coolant loss will cause the engine to run hot because engine is heating less coolant to higher temperatures. The symptom of overheating induced by coolant loss would be a pool of coolant on the pavement when the leak is external. Steam under the hood as the lost coolant hits hot parts of the engine, or a rising temperature gauge in the case of a undetectable engine related leak. Of course, the gauge would also go up if the leaks were not detected. Deteriorated Water Pump:--Cars use a belt driven pump to push the water and coolant mixture through the cooling system. This part is called the water pump. Rarely the impeller that draws the coolant through the pump will rust away making it impossible to push any through the system. If this occurs the temperature gauge will climb and coolant will boil over in the radiator. Inoperable Fan:----Most cooling fans are electrically driven. Some are driven by fan belts. If a belt breaks or the electric supply to the fan is interrupted overheating may result. Electric fans are tuned on thermostatically when needed. When the car runs at idle for extended periods or the weather is extremely hot, a failed fan will cause overheating otherwise it serves as a standby assist to the rest of the cooling system. In stress conditions an inoperable fan will cause the temperature gauge to rise. This will help. Thanks please keep updated.please please do rate the solution positively .thank you for using fixya

sounds to me like the thermostat is sticking and allowing the car to overheat. with the a/c on the fan comes on and runs constantly to keep the engine cool

This is typical of imports to cool the motor down when the car is not moving,as no cool air is entering the engine bay

Make sure that the coolant fan turns on. It should be automatic When the car gets to operating temp the coolant starts to ciculate and the fan comes on. If it doesn't driving pushes air through the radiator and can lower the temp.

This can be caused by a few things. First, the fan motor may be burned out or the temperature switch may be malfunctioning so the fan doesn't engage. The thermostat may also have gone out which prohibits the coolant to circulate through the engine and radiator thus cooling your engine.

The Temp gauge should read in the middle of the gauge at operating temperature. This is normal. The radiator fan should come on after idling (not driving) for 20 minutes. The fan should also come on when you turn on the AC. Are you experiencing overheat problems?
Please reply if you have overheating issues.