I've narrowed it down to probably the heater core. There's no smell in the car when HVAC is off or when AC is on. But when heater is turned on fog comes out of the vents and the windshield immediately fogs up heavily, to the point the windows also fog up. It stays that way for a while. Today I let it run for a long while and slowly the windshield defrosts but much slower than normal. With heat on, there's also an immediate strong smell; not really like coolant though, it smells more like something burnt. Defogging the windshield with AC works much quicker than with heat.
Checked for a heater core leak at the fire wall and on the floor but dry as a bone. No leaks underneath the car either.
About 6 months ago the coolant reservoir was empty. Filled it up during an oil change. Was empty again a week later. Filled it up again and from then on it drops a bit (~20%) every month but I top up.
I suspect I have a slow leak, probably in the heater core. Otherwise there'd be something on the ground. A month back a mechanic told me it could be a slow leak someplace else when the car is running so it wouldn't pool when parked but he said to keep an eye on it. This is the first time using the heater since last winter so I'm guessing it's the core.
Checked for a heater core leak at the fire wall and on the floor but dry as a bone. No leaks underneath the car either.
About 6 months ago the coolant reservoir was empty. Filled it up during an oil change. Was empty again a week later. Filled it up again and from then on it drops a bit (~20%) every month but I top up.
I suspect I have a slow leak, probably in the heater core. Otherwise there'd be something on the ground. A month back a mechanic told me it could be a slow leak someplace else when the car is running so it wouldn't pool when parked but he said to keep an eye on it. This is the first time using the heater since last winter so I'm guessing it's the core.
