PLEASE HELP ME. MK4 V5 OVERHEAT ON LOW RMP

[speedV5]

Hi there. Please sorry for my english but its my first year :-)

So i have vw golf V5 2.3 90k.
I have this car for year and never had problem with it.(till now)
The car starts over heating after 15-20min engine runing (no drive)
the bouth fans are working and you can see them come on/off for like 3times before car start overheating.
So after this 15-20min it come like flash. Temperature is going UP untill i press gas and let the engine go for 2000-3000rmp. Teperature will go down very quickly but only for one min if i not keep play with the engine amd keep in high rmp. If i not the tepmerature will go up in few sec and engine is HOT!!
There is newbthermostat and coolant house.

Any idea what it can be?? Thank you.

[mcgee9t2]

water pump?

could have shed some of the fins on the impellor meaning it cant pump the coolant around fast enough ?

[speedV5]

I was think about whater pump but all people keep saying it will overheat on high rmp not low.

I forgot to say as there is whater blowing in the slim pipe come from whater tank and its going in the engine.
But i not loosing any whater and cant see any funny colors. Also oil looks clean too.