Sounds like you have been through it all ...

Any idea on this (currently dealer is trying to find the issue) I've got an odd one — there’s a light coolant smell in the engine bay once the vehicle warms up. That was traced to the turbo O-rings, which were replaced, but the repair didn’t solve the smell inside the cabin.

When the heat is on, the odor only comes through the driver’s side vents (left-hand drive). The two front vents on the left side of the dash carry it strongly, and in the second row, it’s only present through the left vent on the rear center console (behind the fridge). The passenger-side vents are completely clean — you can put your nose right up to them and smell nothing — but the driver’s side vents have a strong maple syrup or butterscotch odor.

The dealer is still investigating. The system passes pressure tests, but I suspect the issue lies either with the feed into the heater core or a small leak near the firewall where vapor could be getting pulled into the fresh-air intake before being circulated into the cabin.

 

I got nothing for ya unfortunately. If the leak was stopped then maybe there's some residual coolant left somewhere.