PSA electronic thermostat operation

[GiveMeABreak]

Hi and welcome. With fault P2279 AND the following:

1) Does your engine diagnostic lamp light up?
2) Does the cooling fan run at high speed?

If the answer is yes to all these above then check the following:

Check that there are no air leaks in the intake:

• Seal faulty
• Air inlet manifold damaged
• Canister take off damaged
• Hose disconnected

If you have found an air leak, make the repairs and that should resolve the fault.

If there are no leaks after thoroughly checking, the official advice is to reset the timing.

[xantia_v6]

If the low coolant temperature when driving started after you changed the thermostat, then you have probably fitted a faulty thermostat.

It could also be that there is some debris got caught in the thermostat valve, holding it open.

I don't think that the electronic control of the thermostat has 30° of control range.

[Valex76x]

Just updating, this morning I went to work. Coolant temperature went up really fast, reached 96°C, dropped down to 87°, went up to 96°, down to 87° .... this for all the 40 km I did.
So looks like the thermostat is working perfectly now.
Now I need to check if the fan is turning on as it should be.

... and find out the intake air leak

Replying to the questions:
1) Does your engine diagnostic lamp light up?
2) Does the cooling fan run at high speed?
yes and yes

I had both. Don't kill me but, because I had the fan always on, I connected a relay with a small remote control


The thermostat I changed by myself last weekend, what for hell job ! The old one was also causing the temperature rise really slow, probably stuck open.
I did 2 flushing before replace the old thermostat and another one after the new thermostat was mounted only after I put the real coolant Every time I was able to fill only 4 liters instead of the 6.2 that should be. Little bit confused about this. I turned on the heater and the AC every time during the flushing and allays open the valve on the thermostat housing and on the pipe that goes to the heater matrix.

[GiveMeABreak]

Remember the information I provided is applicable if ALL the conditions I mentioned are relevant in your situation.

[Valex76x]

I updated my previous reply, I will check the intake air leak.
A question, the leak can only be after the MAP on the intake manifold right?
I don't have a MAF sensor after the air filter. Only one sensor on the hose after the intercooler and one on the intake manifold.
I have also a "strange filter" and a oil vapor catch cannister on the right side. Can this cause the leak error?

[GiveMeABreak]

You've obviously made some 'modifications' by the looks of that aircraft jet engine attached!

I can't really help you as making any modifications like this can cause issues with the engine management system which is designed to work within set parameters. Modifications to components can result in the air/ fuel measurements being incorrect and throwing errors - like your modification to set the fan speed on high...

Not much I can help you with as these will introduce another level of issues to resolve.

[gwest]

My vacuum leaks have been on the engine breather hose connections but they could be anywhere. Good luck finding it.
And 4 litres is as much as I have ever drained out of my Citroen. The remainder is presumably in the heater circuit and in places around the cylinders in the block that don't drain. If I am replacing the coolant I repeat the drain sequence a number of times with just fresh water until it has considerably diluted the residual fluid. I then add 3.1 litres of concentrated coolant followed by enough water to fill it to achieve a 50% mixture.

[Valex76x]

Today another 40km to come back home and all went fine. Same cooling temperature fluctuation as mentioned before, arrived home I let the engine on and at 100-105°C the fan turned on but not as max as before. So looks like that for now all is fine.
Relay with remote removed for now

About the air filter, sorry but, at 47 years old, my cars are still my toys and I like to play with them I know, I know, the engineers did all for a reason but I'm a technician . Probably I should buy only old cars without too much electronics .

Happy to hear that 4 liters of coolant are fine . I used prediluted coolant, I did all the flushes with distilled water so also if the coolant is mixed should be fine.

[xantia_v6]

The vacuum leak can be anywhere after the throttle butterfly (inclusive). If the breather pipe from the manifold to the engine cover is still present (often blanked off when a catch can is fitted), then the leak could also be in the breather system or engine cover.

[Valex76x]

Now I have the oil catch can only on the right side (rocker cover --> intake turbo). I had another one on the rear (rocker cover -->intake manifold) but I removed it 2-3 months ago so original configuration now. Still not really clear for me what is the best configuration. Read so many variations of this topic that in the end I really don't know

I replaced the rocker cover one year ago, the previous one was leaking oil. Question about the rear small hole: what is it? The red plug should be removed right?
When I have time I will do some leak hunting (probably not the right terminology ).

[xantia_v6]

Most of the oil vapour which ends up as carbon on the intake valves comes via the breather to the intake manifold, so I don't think that your current configuration is ideal. for the purpose of eliminating possible leaks, you could temporarily blank off that path. The downside to blanking it off is that the crankcase is no longer kept at negative pressure and any tiny oil leaks suddenly become obvious.

[Valex76x]

From what I previously read, I thought that the back breather was only for when the motor is at idle. Driving, the pressure on the intake manifold should send the air/vapor out from the right side breather. I drive 90% on the highway, that is why I removed the back breather can. Probably everything wrong

This morning I did the diagnostic (with the App Car Scanner Pro) and the intake leak is gone. Will see if it pops up again in the future.

Just curious, do you know what is the small hole on the back of the rocker cover?

[xantia_v6]

On a standard engine, the rear PCV path operates when manifold pressure is below atmospheric, and the front PCV path operates when manifold pressure is above atmospheric.

I am not sure where the crossover point is while driving, but I think that manifold pressure is below atmospheric when cruising at any legal speed.

There is a partial explanation of the red tab at: https://www.ecstuning.com/b-bremmen-par ... 46555~brp/

[Valex76x]

Yes, you explained better than me . Sorry for my poor terminology .
I have the app always on and I can confirm that cruising on the highway the boost gauge indicate just 1bar = atmospheric pressure.
Only accelerating the pressure goes up.
I will place the rear breather can back.

I checked the old rocker cover that I replaced and the small hole on the back is open. How is it on your 308CC?

[xantia_v6]

I think that it is also open, but I can't check now because I am in a different country than the car.