XigmaTek HDT-S1283 - Red Scorpion

Hi
I purchased this cooler few days ago, I've installed with some problems but thats not the case. The thing is that when I first started my pc to run with new cooler, the core temps on stock voltage and mhz were about 30-35 C on idle and 45 under full load.
So I thought cool it works the temp went dramasticly down.
After 30 mins I overclocked my Q9550 to 3.60 on stock vcore. the temps went 2-3 up. And then i went to 4.0ghz on 1.336vcore, temps went up to 50 on idle and 75 on full load, a lot of heat;//
Final sentence, I thought its too much for the cooler so i went down to stockvcore and frequency, but the temp are still the same!! 50C on idle and 65 under full load, whyy it is so high? Could you help me please?