Ok, I recently changed out my heater core and i've been having this problem ever since. The air doesnt get hot, more like...luke warm. Thing is im freezing out here but i dunno whats up. The coolant levels check out. I searched and a guy said that a bubble might be in the system. So I followed the instructions but nothing. Whe the bleeder "bolt" is removed, it squirts out a little bit, then sucks air back down into it. Im assuming this isnt supposed to happen. I checked the hoses and ran water through the core, no clogs anywhere. I thought it could be the pump, but the car never overheats. So I was told it might be the thermostat. Anyone had to change it on a VG? Is it a PITA or should I get someone to do it? Also, if everything works, would it be wise to just get the system flushed?

 

Check the heater "****"
It is a vacuum actuator operated valve that cuts the water from the heater core when the air is set on max cold. If it's stuck partially shut, you will not get full heat no matter what you set the controls at.

Good luck,
John