I'm working on a Nissan Sentra 1.8L that has no heat. One of the heater core hoses stays cold. I can get heat in the other. I have replaced the thermostat and the radiator cap. The motor temp comes up to normal. I have a bottle of radiator flush in it and have filled the system multiple times. It seems to be a never ending supply of air in the system. I have topped it off and still it will bubble out air from the system. I pulled the plugs and they are all dry and normal looking. I'm at a loss as to where the air is coming from. Any ideas?
I know it is a Nissan but the Nissan forum is empty and I'm not expecting to get any help there.
thanks

 

Maybe the inline heater switch or Control is bad, not allowing flow through the heater core.

 

That's what I origionally thought until I touched the heat hoses. One hose will get warm, the other hose stays cold. So the heater core is not circulating and getting warm to even worry about the controls just yet. It seems to have a never ending supply of air in the system but, it's not emptying the res now. The carpet is dry too.

 

Seems to be that you have a blockage somewhere along the heater hose, instead of buying flush id just replace the hose itself, if your seeing bubbles then you also have a very small leak (just enough to pull in air) along that line.

 

An update: I bypassed the heater core and just connected the two hoses together. They both run hot and no leaks. I bypassed the throttle body. No leaks. I bypassed the tranny cooler. No leaks. Yesterday the car was driven for about 40 miles and went through 1/2 gallon of water. It completely emptied the coolant res and dropped a quart in the rad. And the water still looks like apple juice. The oil looks good. The car does not run hot and it doesn't appear to smoke. The plugs looked good and the top of the cylinders looked good. There are no visible leaks.
This weekend I'm gonna hose down the radiator with some magic bubble to see if it will blow me some nice bubbles somewhere. Maybe try to rig a home brew pressure test too.