Hey guys. Have a 1999 323i. Yesterday while i was on the highway i noticed the yellow coolant light come on. It came on for about a minute, then shut off. I got worried. Pulled over to gas station and let it sit under the bright light for a few mins, revved engine a little, turned heat on, turned heat off, drove forward, backwards... etc.. didnt spot any leaks on the ground. Didnt spot any under the hood either. Temperature never raised on the gauge at all. This morning while engine was cold i opened the coolant cap to the expansion tank (i think thats what it was, the black plastic reservoir near radiator) .. it looked a little low.. i could see coolant at the very bottom and the little level thing was still floating on coolant, but the actual neck wasnt filled. Its dark here now and didnt take pics, i apologize.. but what should i be looking for assuming i dont see any visible leaks? And the fact the car isnt overheating makes me believe its nothing major like radiator or water pump. I read about hairline cracks in the expansion tank? Any advice would be appreciated. Thanks in advance!