My heater hose started to leak.It had a hole in it. So I decided to take the hose out, but the hose connected to the firewall has been giving me problems. It won't come off. I'm wondering, is it suppose to come off? The hose connected just below the oil filter caused me no problems to take out, but the side on the firewall is.

 

It is supposed to come off, but you need to be VERY careful removing it. That connection to the firewall is the heater core nipple -- it's pretty flimsy & easy to break if you try manhandling that hose off. Then you'll have a MUCH bigger problem to fix!

Best way to remove a stubborn hose is to slit it lengthwise with a sharp blade in one or more spots where it goes over the nipple. Then you just peel/twist it off. Good luck!