[AK0405]

2017 BMW 540i
52k miles

Hello,
So basically a few months ago (approximately around 2k miles ago) I had gotten a “top off engine coolant” warning sign, I had some extra coolant, so I topped it off. A few months later, I had gotten the warning once again after not driving it for a few days, I was a bit concerned and once I checked the resovoir tanks, the smaller one was at minimum, while the larger tank was completely dry. I had again topped off both tanks and closely monitored this time around, now it’s been 3 days since then, I drove it over the weekend and it sat for the entirety of the 3rd day. This morning, I had again received the warning, once again I checked the tanks, the smaller one was fine, but the larger tank lost a few ounces of coolant which I topped off again. Now I’m very concerned and plan on taking it to the dealership in the coming days, but I was hoping someone could possibly advise me on what could be happening. Any input would be much appreciated!
Thanks.

[AP]

Common issue unfortunately. Just look through these fthreafs here
Reservoirs are one possibly, look for residue in the engine bay. These are if standing in front, at the front on the right hand side.

Othe possibilities could be a damaged radiator? Maybe see when front grills are open.

[adhrp]

There's clearly a leak. Could be an expansion tank leak, turbo coolant line leak, radiator leak. I would not be driving it. Take it to a dealer if under warranty or indy shop ASAP. Many of us, including myself, have had this happen. Probably the most common known issue on these cars.

[ezaircon4jc]

Could also be a slow cap leak. Look at the top of the reservoir and under where the cap lives for a white residue.