Lower radiator hose clamp broke dumping coolant. New clamp, filled reservoir let it run for awhile. Topped it off. Today's 30 min trip resulted in a Check Coolant light. Checked tank, still coolant there. Any thoughts?

 

Connector loose or dirty? Stuck float? Good luck.

 

Not sure. Where is the float, in the overflow tank?

I purchased this E55 back in 2015. I have never had an issue with coolant. I also haven't ever seen much in the fill/overflow tank until now. The bottom radiator hose clamp broke and drained the system. I have added 1 and 3/4 gallons at that time. This brought the level in the overflow to reach the top black part in the front. Reading the manual, that is the Ideal position. I have monitored after the first few drives and it has been staying in that area.

Yesterday's round trip was a total of 25-30 miles and near the end is when the check coolant level came on. I checked, no difference in level. I carefully opened the tank cap and allowed some air to escape. Haven't driven it but a few miles since, no more light.

 

I think so, yes. It might have just burped some air or become un-stuck. It does take some time to get the air out of the systems.
I would keep an eye on it, maybe check before you drive for a few instances.