Yes, the direction of flow through the thermostat matters. However, if you have the upper radiator hose going to the t-stat housing, if will flow correctly. As far as the heater core, I wouldn't think that would affect anything. However, I've never been asked this question in 30 years on the job.
Now for the "heater control valve, " it doesn't exist on this vehicle. You have what is called a blend air door that determines if you get heat in the vehicle. It is located near the heater core. In one position, it allows heat to enter the vehicle, and in the other, AC can enter the vehicle. If it is stuck in the wrong position, you won't get heat. Do this. Start the engine, turn the heat on high, and let the engine warm up. Feel both heater core hoses. Both should be hot. If they are, you have good flow through the heater core and the blend door is most likely the problem. If one is hot and the other is slightly warm, chances are the heater core is plugged. When the engine cools off, remove the heater core hoses and spray water through it in both directions to see if there is flow and to clean it out. That usually does the trick. Also, make sure there are no air pockets in the system after you do this. Allow the return line (to the intake) slightly loose for air to escape before fully tightening it. You will lose a little coolant, but that is what I recommend trying.
Sunday, January 16th, 2011 AT 2:49 AM