It's a shame your heater core had to be replaced on an '18, obviously a defect not from wear. I'm thinking they had to pull the whole dash out to do that "Hopefully not" in case mine goes out.. On my '18 I'm losing about 1/4 inch of coolant from the bottle every 4k miles. No odors, leaks or mixing with oil issues just wondering if this is a little normal evaporation, no real emergency . I'm in Vegas Hot hot hot...Got my van back home today. They replaced the clamp kit-heater core tubes and core heater.