Cooling Fan Problems

[John15]

Hi. I have a 2002 Citroen C3 1.4 petrol. For several months I'm trying  to solve a problem but fail. After 15-20 minutes of operation temperature indicator rises sharply from 3 lines to maximum, radiator fan starts and stops after a few seconds (perhaps after liquid have cooled), then the temperature returned to normal. Some mechanics told me that the cooling fan is faulty and therefore should be changed. Others said that the temperature sensor is faulty. Today I wanted to see where this sensor is but I could not find him. In the attached picture you will see two sensors, noted with A and B. I mention that after I unplug  sensor A, the fan starts suddenly but does not stop , stopping only when I pluged it back. In the second picture you can see that the cooling fan has a small block. Mechanics said that the cooling fan would not go without it. What should I do/change? Thx.

[paul.h]

Welcome to the forum.

 

On our 2003 C3 1.4 petrol on a couple of occassions the temp jumped to max but I could not find anything wrong. Others have also reported similar. It could be an electrical glitch. First time I stopped the engine and let it cool down. Second time occurred 2 years later and I put the cabin heater on max, opened the windows and carried on at a slower speed and the temp gauge did come down. Later on I replaced the timing belt but also replaced the water pump, the thermostat and anti freeze and it did not happen again. Before this I checked everything including the temperatures using a code reader with live data. The old thermostat when checked opened at the right temperature.

 

On the 1.4 petrol engine there are 2 temp sensors as you have found. The top one does the gauge and the side one is a high temp warning that also puts the gauge to max. Both start the cooling fan. If one sensor is faulty you would not know which it is so both may need replacing. Your fan is working so there should be no need to worry about it.  Relevant temperatures are

- thermostat starts to open 89°C, full open 101°C

- high temperature warning from side sensor 118°C

- expansion tank cap pressure 1.4 barg which is equivalent to 126°C steam

- engine fan cuts in at 96°C and out at 94°C. At a higher temperature it has a higher speed. The air con also runs the engine fan.

 

If you have a code reader with live data you should check the temperatures at which the thermostat opens and the top radiator hose starts to warm up and then when the engine fan starts/stops. Also check the temperature when the engine is cold and as it warms up to see if they seem normal. On our C3 2 bars on the gauge were about 70°C and 3 bars from about 80 to at least 96°C. Doing this will give you confidence that there is nothing wrong or could point to a faulty thermostat or sensor. Also check the radiator is not blocked with something so the air flow is reduced. Code readers do not cost much, as an example https://www.gendan.co.uk/product_FXNT200.html

 

Following is a list of possibilites that can be checked:

- sensor fault or the wiring or electrical connector

- thermostat not opening fully

- radiator blocked internally or externally

- anti freeze needs replacing

- water pump fault so the coolant is not being circulated

- radiator fan not running

- coolant level low or air in the system