Hi. I changed out my heater core yesterday new o-rings etc no leaks. The new issue is a smell coming from the vents when I turn the heat up. I ordered the nissens heater core from FCP Grotten. The smell is not sweet, it reminds me of grease or similar. Could this be adhesive from the foam weatherstripping that came with the heater core? I took it out to look for any grease I may have transferred to the unit and it is clean. Anyone else have the same problem or a solution? I reused some of the old foam to better seal around the core and the housing also (maybe the source? didnt smell like this before the new core). Gonna do some more sniffing around.

 

Maybe it is just the coating burning off the core.