Thread: Engine temperature not stable. Moves between 90-100 C

Hi,
I'm new on this forum.
I have a 407 from 2006 and I have a problem with the temperature gauge. It's 1.8 liter gasoline engine. I drove it around 80.000 km
What happens is that the temperature moves between middle (90 C) to more than one line up (around 100 C). It takes 1-3 minutes to get to 100 and then 1 min t get to 90. This repeats continuously regardless of activity, AC or whatever.
I took the car to service (Peugeot dealer) for several times. Their conclusion: "Is a mystery".

History:
1 - Since I've bought the car the temperature was one line above the middle but stable. Asked service reply was that is ok.
2 - after one year the temperature didn't rise anymore so they replaced the temp sensor and thermostat.
3 - after another year or so same problem but it recovered after one day. After a few months again temperature didn't rise and then it recovered by itself. I took it to service they've replaced again the temp sensor and thermostat. All this time the temp stayed one line above the middle.
4 - From that point the temperature for the engine started to oscillate. It was checked several times no problem found.
5 - It happened again that temp didn't raise but it recovered by itself

I have another problem with the car but I will open a new topic.
Thank you in advance for you're help.

Hey. I am experiencing the same problem. I have a 307 2.0 gasoline ( essence ) and my temperature needle also oscilate between 90 and 100. I have asked everywhere here, but it seems that this is how they work. A gasoline engine's coolant temperature will never stay put in one place like a diesel car. As long as the temperature doesn't go to the grayed-out place, i think its ok.