Peugeot 206 cooling fan

Change speedometer assembly. Best to scan with scanner first.

You may have a cracked cylinder head or damaged head gasket.
Open the coolant bottle and rev the engine, if you see bubbles and get an exhaust has smell then you probably have trouble.
Unless you are very mechanically inclined or better yet a mechanic, it’s not recommended you try fix it yourself.
If you don’t pick up any bubbles or exhaust gas smell, you may have a blockage or even an airlock in your cooling system

it could be you have an air lock in the cooling system
remove the rad cap from the rad, start the engine and let it run until the coolant drops (add to fill it back up) or until the coolant boils out of the rad spout.

maybe pull the heat sensor. -replace it OR clean it off, reinstall it.

Make sure the coolant level is correct. If it is, could be a bad water pump or a clogged radiator. Check the radiator to see if it looks like the inside has a lot of scale and deposits. Remove some coolant if necessary. If the radiator looks relatively clean , could be a bad pump.

1. Check the coolant level if you have not already.

2. The most likely cause is a stuck thermostat so that when the engine is getting up to operating temp the thermostat is not opening at all - or enough - for the coolant to flow freely between the radiator and the engine to cool the heated fluid. If you check the radiator after driving and find it is cold it is a sure sign that the heated coolant that is circulating through the engine at operating temp and higher is not getting to the radiator. The first thing I would do is to change the thermostat and re-check. At the same time completely flush the coolant and replace it with new fluid of the correct spec.

The radiator fans are not going to operate when the fluid in the radiator is cold because the hot fluid cannot flow through from the engine. The fans have a temperature sensor switch.

3. If that does not solve the problem I would suspect the water pump has corroded and needs to be replaced. However from the symptoms you have described I believe a new thermo will fix the problem.

4. Don't drive the car when it is overheating. This is a certain way to blow the head gasket and potentially crack or warp the cylinder head. (In a worst case you can crack the engine block.) It will be nice and expensive to repair if you blow a head gasket or damage the cylinder head.

Yes, it's an easy replacement. Just put a wrench or socket on it and unscrew it. Get a replacement at the dealer, or any parts store should have it or could order it for you. Usae a wrap of teflon tape (or plumber's putty) on the threads of the new unit to prevent leaks.
Location varies, but it will be on top of the engine in a coolant passage. Check around the thermostat housing.

The sensor for the gauge could be faulty.
The thermostat could also be faulty, there is a small window between the thermostat opening at 195 and the coolant boiling at 220.

firstly you need to check the coolant level and make sure there are no air bubbles in the cooling circuit
secondly the thermostat could be damaged and stays in the closed position
thirdly the cooling radiator could be clogged and it must be flushed or replaced
you have to take into accont that it could be a faulty message sent by faulty temperature sensor or bad connector of the senser
so you need to open the hood and decide, is the engine very hot or is it normal but still the fan is on

Did you flush the radiator when you replaced thermostat too? Sounds like it's clogged and the coolant is not circulating as it should. It probably needs to be rodded out or replaced by now.
Check your cooling fans for proper operation. Make sure the outside of the radiator & condensor are clean, and not full of bugs & debris...I hope this helps.

my 528i does, or did the same thing. Overheating is bad for those aluminum cylinder heads. 1st, replace the coolant. Then check to see if the electric cooling fans work, or cycle on, they most certainly would have to cycle on when the temp gauge is in the red zone.
1st thing most people do is replace the thermostat. However, if the temp goes from overheating to not overheating in less than a minute, the thermostat is working. The key thing to look for is why did it get to the red zone in the first place.