Sudden overheating on long road

First of all, hello to everyone, I'm new to the forum. I have a Peugeot 206 1.4 x-line petrol & gas vehicle. There is no problem in the city, the temperature is between 90-100. On the long road, especially when going up the ramp, when the temperature is below 90, it suddenly reaches the end and the stop light turns on, the high fan turns on. But the car has no temperature gauge. It goes back to normal once you cross the ramp. It now does this while driving on a straight road on a long road, and from time to time, I reduce my speed to 70 when driving at 110 and it returns to normal. Fan relays, sensor, thermostat etc. have all been changed but I could not solve the problem. Does anyone have an idea?

Have you checked the circulation and radiator conditions?

no sir. If there is a problem in the circulation, will the car overheat? the car does not overheat for me, the indicator rises for a moment

The problem may be due to the water not rotating at sufficient speed. If there are water channels in the block, water hoses, tube, there is a blockage in the regulator or the radiator, if there is no blockage, it may be due to the failure of the water pump to fulfill its duty.

The inner fins of the circulation pump break over time, which can cause a malfunction, or it could be the cylinder head gasket, which can cause the temperature to rise when it is forced to do so.

Sir, I experienced similar situations in 2019. I recommend you to have your brain checked.

First, replace the water pump. I had a similar problem. When I disassembled the water pump, I discovered that the fins were corroded and melted. The next step is to have the temperature sensor checked.

Thank you so much for everyone's answers, but I can't explain this situation to anyone. The gauge suddenly hits the limit but the car isn't overheating. I found a mechanic in Şaşmaz who has the same problem. He had this problem with a car that had 40,000 km on it and tried everything but couldn't find a solution. There's another guy who has the same problem and said he's been driving like this for 3-4 years and hasn't had any problems, but it's inevitably frustrating. When I explain the situation to the mechanic in the industry, he acts like the car is overheating, but I can't explain it. :)

My friend, my car was doing the same thing in 2019. The overheating would skyrocket, the stop light would come on, and then it would misfire. However, the car wasn't actually overheating. I even opened a topic here in 2019. I changed many parts, and the brain was changed lastly, and the problem was solved. So, I recommend you to have the brain checked.