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Yellow coolant light illuminates off/on. Only on highway

8K views 3 replies 3 participants last post by  jfoj 
#1 ·
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!
 
#2 ·
Might just be a bad coolant level sensor, however, you may want to make sure you do not have any air in the cooling system.
 
#3 ·
It might just be that your coolant level is low. Add some BMW coolant and make sure you bleed it. Don't overfill either. Look for a how-to in the forums if you are uncertain on the process.

If the light still comes on after you have re-filled it, then it should be more of a concern. It is also a good idea to do a coolant overhaul if it has never been done on your car (preventative maintenance). Like you said, hairline cracks can cause leaks.
 
#4 ·
BTW, if you want to try something, the windshield washer level sensor is the same as the coolant level sensor, you could swap these, but it is not easy to access these sensors to swap them.
 
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