Hello guys, new owner from a month here. My bm is e53 3.0i from 2001. In the cold wheater now i can see a problem with my heater. When i start driving in the morning everything is fine, heater is setup to 22-23 deggree (celsius) and its perfecly fine for about a 15-20 mins. of driving (nice and worm). After that its starting to blow cold, so im starting to increase to 25-27 degree and its again fine for about 5-10 mins, and i need to increase again till 31 and again same story blowing worm for 5-10 mins and again its cold... BUT if its setup to 32 its really worm... so 31-31.5 cold but 32 verry worm ?!...OBD scan shows no error codes, engine temp is on the middle, the cooling liquid is on max, i check for air in the cooling system, there is non.... can anyone tell me what it could be ?