Help with Heater Core

The other day, I went to auto parts store, and I bought coolant to match my Tacoma because I noticed the level in the reservoir was low. I filled it to the fill line. Now I find my heater is raspy as if there is a small amount of fuild in there, and the floor mat is wet with what I assume is coolant.

Did I over fill the coolant, or could the coolant I used have harmed the heater core? Or is this simply a case of my heater core being old and going bad?

 

Thanks for your time!

 

Could be that your heater core is leaking.

But are you sure it is not condensation from a windshield leak or AC clog leak?

Is the floor mat wet from above or below?

 

It has been raining a lot here recently, but it doesn't seem to be leaking from above.