So I narrowed it down to the heater core hose that connects to the water pump outlet pipe. Its not getting hot. The other hose is hot.

So what does that mean?

I can ramp up the RPMs and it starts to get hot and I have heat. I haven't really had a chance to drive it around to circulate the water, but it should be getting hot while idling.

note: I was really low on my coolant level and just filled it up to the line. Do you think that I'd have to drive it around more to get it to start circulating properly?

 

There might be an air pocket some where in the hose. It happened to me one time when I changed my coolant.

 

Follow these instructions:

Step 1 - Allow the cooling system to reach ambient temperature. To do this, simply turn off the truck's engine for at least one hour.

Step 2 - Open the radiator cap and set aside.

Step 3 - Turn the truck engine back on.

Step 4 - Turn the heat to "Max". This will allow the coolant to flow through the heater core, so that all air pockets will be removed.

Step 5 - Squeeze the upper radiator hose while the truck engine is on. This method is called "gulping," and helps in eliminating air pockets.

Step 6 - Rev the engine up to 2,000 RPMs and hold for about 15 seconds, so that the cooling pump pumps fluid through the system at a faster rate than when engine is idled. Fluid will be forced through the system and will bring all the air pockets up to the radiator, thus purging the air out of the radiator. Repeat this step about 2 to 3 times.

Step 7 - Close the radiator cap.


That was the way I did mine. Took me a day or two to make sure it got back to factory fill levels though. I just kept a bottle of motorcraft coolant with me when I'd check it.

I can tell ya, flushing it will improve your heating!

 

Make sure you have enough coolant. The overflows really don't give you much of an indication - My '06 Exp. showed full cold, but same problems - no or intermittant heat. The radiator took over a half gallon of coolant. Did a pressure check all good - so look to fluid levels first.

 

your heater core may be clogged. if you dont use enough antifreeze you get that orange corrosion type stuff and it gets stuck in the heater core. the water may be going in but not coming out. the heater wont work very well at idle. you have to drive it to really get the engine spinning and hot. if the temp needle is around the "C" and not really getting up to about 1/4 or 1/2 then you wont be getting heat either. it takes my truck about 2 miles of driving to really get hot. it will not get hot from just idling. the engine must be hot enough to open the thermostat and allow that hot water thats inside the engine to flow. sounds to me like you dont have any problem to worry about just yet. try driving it around for 2-3 miles and see if it gets hot. if it doesnt then its your heater core which is located behind your glove box.