DS5 2.0 Hybrid - Overheating & Temperature Issues AFTER Engine Shutoff

[rkomzz]

Hello everyone,

I’ve been having a strange problem with my car Citroen DS5 2.0 hybrid, and think it has something with thermostat. The engine temperature stays steady at 90°C during driving every time no fluctuation , which seems normal, but after I turn off the engine, if it’s been well warmed up the temperature starts to rise. If I start the car again it get back to normal almost instantly.

What’s also weird is that the area around the engine feels noticeably warmer when I open the hood, even though the temperature gauge still shows 90°C. Sometimes, the radiator fan also turns on in these cases, which I assume is normal, but still, something doesn’t feel right.

I’ve also noticed that after the engine is properly warmed (driving a while with 90°C), the fuel temperature reading on my cheap ELM327 adapter starts rising as well.

So, I'm assuming that this is the kind of overheating issue...... The problem only seems to happen when the engine is properly warmed up. The mechanics I’ve gone to brush it off, saying everything is fine, but I know something’s not right.

I suspect stuck thermostat in slightly open position or failure of electronic part, Has anyone experienced something similar, or have any ideas on what could be causing this?


Thanks

[mickthemaverick]

I'd say it is not unusual for an engine temperature to rise as soon as it is switched off, for the simple reason that the coolant is no longer circulating enabling it to take the engine's core heat away. Once the coolant has settled the radiator fan running will cool the coolant in the radiator, which in turn means the heat still in the engine side coolant will work its way to the radiator by conduction through the system to try and balance the heat taken from the radiator. Thus once the temperature is below the thermostat's rating it will close and cut off that conduction path leaving the rest of the cooling to be achieved by natural radiation from the engine itself. The ecu will detect that closing and turn off the fan as it no longer has conducted heat coming through to cool and is therefore pointless!! At least that is how I believe it works!!

[rkomzz]

I truly appreciate your response and understand your point, engine temperature can rise after the engine is turned off due to the lack of coolant circulation.... I still don’t think this is normal in my case.

The fuel temperature, for example, is rising above 70°C during driving, but only after the engine has been fully warmed up. Additionally, the FAP app shows an increased temperature in the AirManifold section at the same time. I also forgot to mention, after the engine shuts off the coolant temperature quickly climbs above 100°C and maybe would heads toward the red zone, but as soon as the engine starts again, it returns to normal.

I change the coolant every 2 years, so I’m wondering if there could be an issue with a clogged radiator?
I was also thinking about replacing the entire thermostat housing with the sensors, do you think that might help?

[PaulC5]

I suspect there is nothing wrong and if you did not have a code reader with live data you would be none the wiser. You could let the engine idle for a minute or so before switching off to see if it helps and this should be done anyway if you have a turbo to allow it to slow down before stopping its oil flow when the engine is stopped.

When you replaced the timing belt (due at 10 years so in 2024 or a mileage if sooner) did you also replace the water pump, just asking in case there is a fault with it ?

It is normal for the inlet air temperature to increase as the engine warms up, I have seen up to 40°C on our cars from about 20°C before starting. I have not had a car that shows fuel temperature so cannot comment on that.

[rkomzz]

I suspect there is nothing wrong and if you did not have a code reader with live data you would be none the wiser. You could let the engine idle for a minute or so before switching off to see if it helps and this should be done anyway if you have a turbo to allow it to slow down before stopping its oil flow when the engine is stopped.

When you replaced the timing belt (due at 10 years so in 2024 or a mileage if sooner) did you also replace the water pump, just asking in case there is a fault with it ?

It is normal for the inlet air temperature to increase as the engine warms up, I have seen up to 40°C on our cars from about 20°C before starting. I have not had a car that shows fuel temperature so cannot comment on that.

It's been at least 3-4 years since the timing belt and water pump were replaced. Could this be the cause?

[xantia_v6]

I don't think that you have described any condition of overheating. When the engine is running normally, the water temperature is 90, the oil temperature varies, but would typically be 90 to 110, which would also be the temperature of the bottom end of the engine. The turbo will be somewhat hotter.

When you switch off the engine those temperatures tend to even out, which raises the coolant temperature. The heat is largely dissipated by radiation to the rest of the engine bay.

[PaulC5]

When did you start to think there was a problem, is it when you obtained a code reader and plugged it in to see what the sensors were giving ? I still think there is nothing wrong though.

[rkomzz]

First of all, big thanks to everyone for trying to help!

I'm not exactly sure when the problem started, but at some point I began to notice a slight burnt smell mixed with heat after I get out of the car and walk near the hood.

I then connected an ELM327 adapter and monitored the parameters while driving. I saw that when the engine gets properly warmed up, the fuel temperature rises to 70-80°C. I also forgot to mention that at that point, electric mode becomes unavailable and the diesel engine keeps running continuously. Subjectively, it also seems like the engine develops a slightly rougher sound.

[PaulC5]

If the burnt smell is a bit like a curry then that could be a coolant leak so you could check all the pipes, engine, the cabin heater. Other burnt smells could be an exhaust leak or oil on something hot or possibly a seized brake.

[rkomzz]

Brakes are OK.
Oil level is OK(at the same level).
Clutch is OK.
Turbo is OK, operating properly, the car doesn’t go into safe mode, and sound isn’t noticeable..

In general, the engine runs fine, except that after driviing for a longer period at operating temperature, it seems like performnace temporarily drops because of it. I’m not sure as it been happening during winter, but I only noticed it after the arrival of warmer days.

As for the Coolant, I change the coolant every other service, every two years (last '24),
I haven’t noticed the huge level dropping, but i do top it up with a few deciliters between changes. Is it possible for the system to remain improperly bled for this long, but that doesn’t really make sense?

[rkomzz]

After a short run, coolant temp is 81°C and car isn't fully warmed up yet, but the fuel temp is already 77C, how is that possible?