Macbook Air overheating

Got a strange problem. ...

What's wrong with this Macbook Air 13,3" mid 2011

Who can help me into the right direction?

Is the fan broken or something with the fan control? I'm a bit lost.

I already cleaned the inside and replaced the cooling paste

And putting the macbook on the airco to work is starting to get cold....

So far I concluded:

- Temperature sensor seems to be working. (smcFanControl seems to report is quite well)

- Fan seems to be working. (opened the bottom, can see Fan is working)

- Fan speed control (with smcFanControl) seems to be working

- Reset the SMC and did a hardware test which all said OK. (*)

- Reinstalled osX to go back to basics. (*)

(*) Macbook on top of an AirCo, otherwise it overheats and shutdown with 2-3 minutes

Temperature:

Standard without smcFanControl enabled:

2000 rpm...I can see the temperature goes up to 80+ Celcius until Macbook shutsdown.

And somehow even with the fanspeed going up...the temperature doesn't go down.

With smcFanControl:

2000 rpm 80+ Celcius until Macbook shutsdown.

2200 rpm 43 C

2400 rpm 42 C

2600 rpm 48 C

2800 rpm 50 C

3000 rpm 52 C

Temp was measured after 2 minutes at set rpm. Weird enough...the temperature doesn't go down when speeding up the fan.

(Measured all after clean installation and smcFanControl installed, no other apps running)

Would it be smart to first replace the fan? Or do you have any other suggestions?

P.S. I read all the other threads about overheating. But somehow this problem is a bit different.