I had a wet carpet, antifreeze smell, and fog on the windshield. My mechanic replaced my heater core. Off on and on I still smelled antifreeze but no fog anymore. I waited 2 weeks for the smell to go away. Maybe residue. Then I smelled it strongly with my heat and blower on one night and took it in the next day. The antifreeze in the reservoir was almost empty. The mechanic filled it. He has had it a couple of days and says he sees no leak or the coolant down. He doesn't smell anything. Anybody know what's going on? The car is a 1995 volvo 940. I'd appreciate any help in how to deal with this.