Overheating

[qman3428]

My 2009 C5 2.0 HDi has over heated in traffic twice in the last week ( weather must have got better)

Each time there was no activity from the fan. I am told the sensor is on the thermostat but I cant see it. I was also told that if I disconnect it the fan should come on which would discount it as the fault

 

Any one got any ideas

[paul.h]

If you have a code reader that shows live data it will give the coolant sensor temperature. I could not find any values for your car but for our C3 the thermostat should start to open at 89°C, the fan should cut in at 96°C and cut out when back down to 94°C, a high temperature warning at 118°C, the air con is cut out at 115°C, the expansion tank cap should lift at 1.4 barg which is equivalent to steam at 126°C. When running normally it was always about 90ish, the gauge uses 6 bars to show a range of temperatures and did not go above normal when the fan started.

 

Disconnecting the C3 sensor only brought up a fault code of an unbelievable value so I do not know if it would start the C5 fan. Since the sensor has a resistance that reduces as it gets hotter, just disconnecting it would give a greater resistance as though it was getting colder. I also tried bridging the connector to give no resistance and this did not start the fan,

 

So, if your temperature values are similar and a high temperature was indicated by the gauge, then your fan should have been on and there is probably nothing wrong with the sensor. Similarly the thermostat is probably ok, otherwise it would overheat soon after starting.

 

A look at the parts diagrams shows the fan has either a relay or a controller at the fan - maybe this is at fault or has a bad connection/wiring/earth - but if the fan runs when the air con is on then maybe not. If you can get to the fan connector then you could try a 12v supply from the battery direct to the fan to see if it runs (and also check for a 12v supply at the connector). The temp sensor looks to be on an outlet tank at the geabox end of the cylinder head (it may be green). Hoses from the tank go to the radiator. You could also check the fuses but a look in the handbook on service.citroen does not list an obvious one for the engine fan unless it uses a maxi fuse.

 

Until it is sorted, if you see the temp gauge going high, you could open the windows and put the cabin heater on max temp/air flow to help remove the excess heat.

[qman3428]

Hi, I used the heaters to cool the engine this Monday, 30 degrees outside and the heaters on, not nice. I have booked the car for a diagnostic with the main dealer so I will let you know the outcome. It is a typical modern car, I can see the fan but cant get to it without major stripdown. I will look for the sensor tonight.

Thanks

[qman3428]

Ok had it checked out, the fan motor has gone, new one ordered and booked in for fitting