[Marabekm]

I am assuming you guys are talking about 4.13.4 version. If not, then disregard any of this post.

From the Aircraft Guide, located in you game folder:
BF-109K
Gauge 14 --- Coolant Temp (Top right)
Gauge 15 -- Oil Temperature (Directly below Gauge 14)
(I hate to say it treetop, but you got this wrong)
BF-109K C3 ---- Gauges are in the same place.

Now lets look at the Temp Guide, also in the game folder:
For the Bf-109K, its given as 115/80. 115 is coolant limit (gauge 14), 80 is oil limit (gauge 15)

Now I haven't flown the 109 much. I do agree if the engine is overheating, the cooling flaps should open fully. Because I haven't flown this plane, I cant tell if that happens or not. And just a question, there isn't a radiator indicator in the 109, so how are you sure its only opening part way and no fully?

Just some advice, from the same guide:
General flying tips:
Watch your temperatures all the time, avoid using excessive power settings for longer
periods of time. Only stretch your engine when it needs be - at take off, during actual combat.
Use maximum permissible climb settings to get to your desired altitude and cool your engine
down while cruising. The more headroom you’ll have before combat the better - that means that
you can fly at full power longer if you need to. Fly fast - the speed of the outside air is helping
you to cool down your cylinders or coolant. Fly high - the temperature of the outside air is
helping you to cool down your engine, too. Don’t underestimate your environment - hot maps
make it harder for you to keep your engine cool, as hotter air is cooling your engine. Watch your
temperatures at all times and for general advice, please refer to following chapter of this
document for temperatures set on various maps in the sim.


Hope this helps, and like I said, if not using 4.13.4, none of this info is valid.