has everyone forgotten the blend door issue...??
almost certainly your blend door is stuck in the cool position...

Chris

 

I've had to deal with this 3 times now - each time after I have a dealer do cooling system work (who will never touch my truck again). This last time over the weekend, I did some trial and error to help anyone else who has the issue.

Keep in mind I am not even a shadetree mechanic anymore. I'd call myself an alley mechanic now. So caveat emptor.

My theory is that some just don't know how to refill the system and get air out of all the lines. Bubbles in lines aren't good for the engine - or for heating the passenger area. Flushing just the heater core seems to get all air out.

1 - Disconnect what I believe to be the return line from the heater core to the engine (I've circled it in the pic)
2 - Attach garden hose to the hose going to the firewall (I used a brass 5/8" coupler from the plumbing dept at Home Depot and some cut off hose)
3 - Turn on the water
4 - Let coolant flow from the pump connection (make sure to capture it someplace to be environmentally friendly)
5 - While garden hose is still flowing a little, disconnect from the line going to the firewall and quickly reconnect to the water pump connection (goal is to minimize air getting into the line)
6 - Drive around to mix everything and test heating
7 - Check antifreeze to ensure the mix is right - adjust accordingly

That has worked three times for me. But again caveat emptor. I'd like to know if anyone can confirm or deny this is the right approach.

The other thing I did while messing around this weekend was go to a 160 degree thermostat vs. stock 180. Read here that was better but need to go reread why.

While replacing, found the dealer had replaced the thermostat - without my approval or getting charged. How do I know? Wrong gasket and no sealant. Even found some of my old sealant scraped off around the area. AND... the new thermostat was installed UPSIDE DOWN!

Like I said, those yahoos will never, ever touch my truck again.

 

Just remember, if your heater core is ever clogged, chances are your cooling system in general has issues that needs to be addressed.

 

A couple issue I see with your work is that you want to put clean water in your D. The tap water has all sorts of nasty minerals that will cause all kinds of problems for you later. When you flush the core/engine you want the least amount of tap water left in your engine as possible. The other issue I think was just a brain fart. OEM t-stats run 195. I think you replaced with a 180. If you did put a 160 in there you are running way too cold and need to replace it or you will be running in warmup mode constantly which will kill your mileage and most likely contribute to a lot of carbon buildup in the engine.

On a side note I have done the coolant in my D quite a few times already and I am able to get all of the air out of the system by just going straight through the fill port in the upper rad hose. Just run the engine to operating temp while filling the D and it will work out all of the air. To the left of the fill port the hose is a little high and can hold onto some air. Just give that a squeeze every now and then to get the air out during filling.

 

I would not recommend using a 160 stat for every day driving as Mean says. Most critical is that using a 160 stat, you won't pass emissions testing. Those that use 160 stat is mainly for racing applications.