Sounds like your heater core is clogged. It needs to be flushed.

 

Could also be the temperature control is stuck on the cold setting.

 

The drain tube is for A/C condensation to drain out, not coolant. Are your vacuum doors in the dash opening properly? Lower, middle, upper?

 

The vacuum doors are working. I have freezing cold AC that has been great all summer.
I did a flush this afternoon and it is better but not "HOT". I'll flush it again later on and if that doesn't do it, I guess I'll replace it. It's a cheap enough part...

Thanks!

 

Remove both hoses from the firewall and flush the heater core directly. Alternately flush both holes multiple times until the water is coming out clear both ways. I usually will kink the garden hose, line it up over the firewall hole, release kink and let it flush, kink again, put garden hose on other heater core hole, unkink and let it backflush, like I said alternate until it is clean and you should be good. Be sure to undo the lines as to not flush the gunk back into your cooling system.

 

Maybe you should check and make sure that your thermostat isn't stuck open.