I got a Civic Coupe EJ8.

Since I removed my A/C when I turn On the Heat come some smoke from vents and smells like Radiator Fluid Burning.

I've checked hoses inside Engine Bay but I didn't found nothing leaking.

Can be the heater core damaged?

 

Very possible

 

If you smell coolant and see vapor in the cabin. It's the heater core. Probably unrelated to your A/C delete.

 

Yes it smell like heat coolant and some from vents...

To change Heat Core need to remove Dash right?

 

Yes