206 diesel heat problem

2004 206 hdi diesel sw x line model car I bought new 2nd hand. I have no problem on normal city roads and flat roads, but the heat when ramping on the long road & nbsp; it rises very high (above 90 & nbsp; near its 2nd line) and in case of idling, the temperature returns to normal or returns to normal after the ramp. I wonder where the problem might be from. Thanks

very interesting.

The topic has been discussed previously in the forum.

A normal situation is awkward in 206s, it is a pointer :)