Fogged up windows

One thing I can assure you of is that stop leak is really good at stopping the flow of antifreeze through heater cores. Then we’ll see your post shortly complaining about why your heater doesn’t put out any heat, and it’s freezing in your car. For anyone else out there, I’d really not recommend any kind of radiator stop leak mixture, as it does in fact work at stopping up things.

if it was hard to wipe off with a rag,probably heating core.water and antifreeze combo

StopLeak might help until you can schedule an appointment to get your heater core replaced. Don’t use it as a permanent fix, only to get you over those few cold days in the next week or two.

StopLeak might help until you can schedule an appointment to get your heater core replaced. Don’t use it as a permanent fix, only to get you over those few cold days in the next week or two.

Since stop leak products can cause problems themselves, I would suggest getting it in to be repaired now and not try putting it off by using leak stop. Take the bus if needed.