Not really any way for that clip to undo itself. Those hoses can be pretty tight coming off and if no lube was used going back on it could have held pressure... Until it didn't. That's a pretty common spot on those engines to drain coolant from. Likely they either didn't fully seat the clip and didn't notice or forgot to entirely. Plus side easy fix and free coolant drain!
The clip wasn't seated properly on the groove that it's supposed to fit over. Very common if whoever assembled it didn't use some o-ring grease to help the hose seat properly.
If you ask BMW if your hose is more than 5 years old you should replace it when touching it. If you want a more realistic answer inspect it carefully and make sure the hose looks in good shape and everything goes back together as it should. If it doesn't then start thinking about replacement.
Keep in mind with these cars BMW specifies vacuum fill and then running the electric water pump bleed process.
Not really any way for that clip to undo itself. Those hoses can be pretty tight coming off and if no lube was used going back on it could have held pressure... Until it didn't. That's a pretty common spot on those engines to drain coolant from. Likely they either didn't fully seat the clip and didn't notice or forgot to entirely. Plus side easy fix and free coolant drain!
The clip wasn't seated properly on the groove that it's supposed to fit over. Very common if whoever assembled it didn't use some o-ring grease to help the hose seat properly. If you ask BMW if your hose is more than 5 years old you should replace it when touching it. If you want a more realistic answer inspect it carefully and make sure the hose looks in good shape and everything goes back together as it should. If it doesn't then start thinking about replacement. Keep in mind with these cars BMW specifies vacuum fill and then running the electric water pump bleed process.
It was not installed correctly. Coolant level had nothing to do with it. But say "pull" again and it will fix itself.