BMW Repair: check coolent level, coolant level, radiator cap

Question
hi my car is 98 328i. it would display check coolant level. anyways it went into red light. I towed it to the shop and they said i needed a new radiator. i got it replaced. now i turned the car on it was fine. it did not display check coolent level. the gauge was half way between blue and red. when i turned the car of it displayed check coolent level. i turned the car on and it dispaleyd check control, so when i did it said again check coolent level and then i pressed it again and displayed check control ok.  what';s going on. it only does this when i turn it off and on for couple of secs. then it displays check control ok.. should i be worried. the gauge is now half way it does not go beyond this point. pleease help.  

Answer
Sladja, Have you checked the coolant level? Where is the coolant level on the expansion tank. The coolant level sensors at the bottom of the expansion tank have known problems. If the car is not leaking coolant (you must check or have pressure tested) and the radiator cap is good (you need to pressure test or just replace if the o-rings have flatened out by looking at it). Then replace the coolant level sensor at the bottom of the expansion tank with a new one. It is good news to hear you've gotten your overheat condition under control, because our engines can't take overheating for very long.
-Evan