Xsara 1.6 16v , petrol 2003. cooling liquid temperature issue

[Leonman247]

Hello everyone!
I have searched trough the topics but didn't find anything similar, or maybe missed, if so please appoint me to the right topic.

I have and issue with cooling liquid temperature at cruising speed.
The temperature gauge never gets to 90° or even close, always stays at around 70-75°..
When i go for a drive, it stays on this temperature even on the highway, only goes to 90° when car is back from a ride , idling and yhe engine is hot, then once start driving again gets back to 70 area and stays there.
I bought the car like that, and i am willing to solve it.
I have changed the termostat, to an aftermarket one, flushed the cooling system, and replaced coolant with citroen certified one from a citroen garage, replaced the coolant temperature sensor, aswell as the expansion tank cap.
Problem is still there.
Fan starts at 90° when car is stationary.
There are no coolant leaks.
Radiator is a factory one and car in general is in very good condition, with 75000 on the clock.

[Rp0thejester]

Sounds like an electrical gremlin to me. Mine occasionally has the fans running even after a short distance and not hot, I just turn the engine on and off again till it stops, I've never once had it happen after a long journey when id expect to kick in.

[Leonman247]

Whatci mean is that they run when engine reaches 90°, and that's basically only when stationary with hot engine .... But ya it slowly narrows to something to do rather with the electronics, i will get it connected to a OBD, and hopefully there will be some answers

[Rp0thejester]

Well yes, the fan shouldn't kick in before it hits roughly 95, so I'd say it's an electrical issue with the fan, but an aftermarket thermostat may change when it opens/closes

[Leonman247]

But fan is not an issue here as far as i know, fan does it's job and starts when coolant is 90°
The problem is that it never gets to 90° while driving

[Rp0thejester]

That's not the issue, the car is getting plenty of cool air whilst driving, but not whilst stationary. Stupid question I know, but have you checked the air intake from filter to all air pipes? A disconnected/loose air pipe can give those symptoms.

[Leonman247]

I've checked that the plastic hose that goes from the air filter to the engine area is tight cause i had to remove it to get to the coolant bleeding screw...

[Leonman247]

Someone suggested that the thermostat could have been installed wrong, but i don't see how ..

[Rp0thejester]

That's a possibility, have you tested the thermostat? Also what 03 Xsara do you have? Is it a picasso?

[Leonman247]

It's on top of the post the exact model, but no it's not a picasso , just a xsara.
How do i test the termostat? Today i started the engine cold, it was idling until it's about 70° , (the termostat was closed cause i touched the hose that goes from it to the radiator and it wasnt hot, then i gave some gas for couple of seconds til about 3000/4000rpm..
And all of a sudden this hose was hot like if termostat opened, but the temperature gauge was still on the same mark , around 70-75 not more..... What does it means ? Faulty thermostat? Wrong temperature reading?

[PaulC5]

Sounds as if the thermostat is opening at too low a temperature. Typically they will just start to open at around 90°C and be fully open a few degrees higher and should close when the temperature drops back down. You could look up at what temperature it should start to open.

To test it you can do as you have done but use a code reader with live data to see what temperature it is opening rather than the gauge which may not be accurate leading you to believe there is a problem when there might not be. Another way to test it is to put it in a pan of water with a thermometer and heat it up and watch it open.

I have replaced a thermostat before and then found the new one was faulty but it took a while to realise it.

[ozvtr]

I have no data on when the radiator fan should come on, but the thermostat should begin to open at 89'C and be fully open at 101'C.
The engine coolant outlet temp is typically around 90-95'C. In that case I would not expect the radiator fan to come on before 100'C.
Have you put the car on an OBD scanner yet? I bet the scanner shows correct temps and does not agree with the temp gauge.
My guess is that the engine is running fine but the cluster temp gauge is reading 10-20 degrees low.

[Leonman247]

I have no data on when the radiator fan should come on, but the thermostat should begin to open at 89'C and be fully open at 101'C.
The engine coolant outlet temp is typically around 90-95'C. In that case I would not expect the radiator fan to come on before 100'C.
Have you put the car on an OBD scanner yet? I bet the scanner shows correct temps and does not agree with the temp gauge.
My guess is that the engine is running fine but the cluster temp gauge is reading 10-20 degrees low.

That's the best lead so far, because it's the second thermostat I'm changing, but only the first temperature sensor, It would make sense that rather the gauge is lying because according to it the fan is starting at 90 and coolant starts to flow at when the gauge is a bit higher than the 70-75. so the 10-20 degrees difference would make a perfect sense for the system to function as it does now, and did after the first thermostat change.
I will have it connected to to OBD in the next days and see if the system reading confirms it.