I took my 2019 GTI (Rabbit Edition) to the dealership as the check engine light came on. When I hooked it up the computer read out it stated it was a coolant sensor issue. They told me the same thing once I got it into the dealership, said they would order the part and it was safe to drive. That was on a Monday, Thursday I took it in for the sensor to get replaced and after 3 hours of sitting there they came and asked me if I added anything to the coolant, I said no, whenever I checked it it was always at the correct level. Then the manager came and asked me to step in his office and told me when the technician took off the coolant overflow cap the coolant started to bubble out and overflow and then put off a toxic smell like ammonia, they stopped working in it and told me to call my car insurance as it was 3,000 miles out of Factory warranty and they believe someone had to have added something to the coolant to give off those toxic fumes. The car is always locked and I park inside my garage when I’m home. Has anyone ever experienced anything like that? My car insurance is leaning towards mechanical failure. I need some advice. I don’t know a lot about cars and I feel someone is lying to me. It ran and performed flawlessly when I drove it into the dealership.