I had the very same problem and I live in Wisconsin too. One of the quick disconnect connectors that transport hot coolant to the heater core had broken at the firewall. I would never see coolant leak on the ground because it vaporized on the exhaust pipes. It smelt horrible. I cut the original Quick Disconnect connectors off because they would not function. The plastic was broken and the leak was substantial. I replaced it with regular hose and hose clamp. No more leaks and no more burning coolant smells while driving.

 

Thanks for the insight. I looked at the heater line connections but did not see any leakage, but in my case the leak was not as severe as it sounds like yours was. There has been a slight hint of coolant smell so it is possible that there is a small leak at one of those connections that is releasing coolant onto the exhaust.
Unfortunately I don't see the car very often to check out ideas that come forward but I will check it out the next chance I get.

 

When the vehicle was cold, the coolant leak was simply a drop on the bottom of the connector. When the engine was hot, it sprayed like a fuel injector on the exhaust pipe making a sauna! The burning coolant smelt awful, but I never saw a drop on the ground. How I found it was with a very bright flash light and a mirror to see the bottom of the Quick Disconnect connectors while hot. One connector was noticeably broken with the outer shell gone. I had to literally cut it off. The mechanism was beyond repair. They are plastic parts and I would recommend everyone replaces them before they fall apart.

 

I was able to look at the car yesterday and the coolant loss has stopped. I believe it was at least two months ago that I installed the stop leak and filled the reservoir to the full level. Yesterday the coolant level check revealed the coolant level remained at the full level so wherever the leak was it appears to be resolved (at least for now). I will continue to monitor over the summer months as I anticipate my granddaughter will be driving more and potentially longer drives that may increase the stress on the coolant system.