I have a 2004 Expedition Eddie Bauer we bought recently and my wife has been complaining that the heat just doesn't seem hot. I drove it and it's odd because sometimes it will get hotter than other times. Also the AC doesn't seem to be as cold as it should be. I checked the coolant and it was fine. I checked both inlet and outlet heater core hoses and they are hot so I am at a loss of what it could be. I was thinking the blend door may have been broke or stuck but I can change the temp on the dash and it does change temp when I raise or lower the temp albeit not as much as it should. If I have the heat set on 90 and kick on the ac compressor the temp coming out of the vents gets cooler as well. Is this supposed to be isolated from the heater core and the blend door so it doesn't affect the heat?we got our first cold snap and she is on my butt to fix it.

Any ideas would be greatly appreciated.

 

Well, if she's around that age of 45-55, it might be her, not the truck.....

No, it's all in the same plenum by design.

Here's a couple of things you can do to see what might be going on:

Double-check the temp of the heater hoses when the system is on maximum heat draw (temp and blower both as high as they can go, outlet set to floor or vent only). Measure the outlet temp with a small thermometer. Also, if you have an IR thermometer, measure those hose and look at the real numbers. You may have diminished coolant flow through the heater core.

Look at the actual temperature of the coolant hose outlet with an IR thermometer. If the thermostat is sticking open, there won't be enough heat.

If she's usually the passenger, swap sides and have her drive. Look for any air leaks that might be allowing outside air to come in that shouldn't.

 

Nope, not her. I am driving it this morning and it's not hot really. One thing I notice is that when I have it on high blow and heat I get very little air through the vents as opposed to high blow cool. I also hear a lot of wind noise under the dash while on heat. Not so much while on cool and it blows hard on cool. I will check everything you mentioned, just wanted to throw that out there while it was on my mind.

 

I also noticed that the heat in the rear is HOT like it should be. Could the heater core be externally clogged with trash preventing the air from blowing across the coils? That would explain the poor heating and the lack of air though the vents. This vehicle lived outside and was always parked under trees when not being driven. Is there a way to look at the heater core without pulling the dash?

 

Have you verified coolant level?

 

Yep, coolant is good.

 

Next would probably be verify inlet/outlet temps at the heater core. That will tell you if it's a core issue, or a HVAC box issue

 

Yes, that's possible. Pull the blower out and see if you can inspect the heater core (adjust it to HOT before turning off) for blockage.

Catalog the airflow observations for each function selection, both with the temp set to its minimum and to its maximum. Let's look for patterns for when the TOTAL volume of airflow from ALL outlets, whether selected or not, is either normal or diminished.

From that, we can figure out if there's a blockage and where it's at, if the evidence suggests one is present.

 

Checked my heater for hoses for temp and one is running about 125-128f and the other is around 115f. Also cut a small hole in the box next to the blend door behind the glove box to verify it working and the blend door is working fine. It just seems loud when heat is on and fan is on high. Air volume coming out of vents is actually lower than when on cool as well so that has me confused. Checked heat coming out of vents and it was showing around 112-114f for the front and around 125f to rear vents.

As for a blockage, I didn't see one but I have a very nice bore scope at work that I am going to use to verify there isn't anything blocking the core.

 

You can pull both heater hoses use your hand to connect a garden hose to it. You can turn on low pressure and see how it flows through the core

 

Assuming that's the temp of the circulating coolant as measure at a metal fitting, not the exterior of the rubber hoses (insulation factor), that's the reason you have minimal heat up front. Those hoses should be 190F+ when the engine is at full operating temp.

Probable causes:

Low coolant
Air bubble in heater loop
Weak pump (eroded impeller)
Thermostat stuck open

...and the biggy - a restriction in the heater loop.
This might be due to a partially plugged heater core or a kinked or internally collapsed hose. Also, IIRC, there's a restriction somewhere in the total heater loop that is supposed to balance the coolant blow between the front and rear. The details of it as well as its specific symptoms eludes my memory ATM, but I do recall there is such a critter in the system.

 

Well, I did take that reading on the rubber hoses so that may be why its lower. That being said, I am now thinking it may be a partially clogged Heater core. When sitting at a light this morning I noticed the hot air coming through the vents cooled off slightly. I placed it in neutral and increased the RPM to about 2500RPM and it warmed back up to where it was. Does that sound like symptoms of a partially clogged core? I plan on doing a coolant system flush and replacing the thermostat this weekend. Hopefully that will help clear up the problem. I am pretty sure this has never been done since it was new.

 

Not necessarily. The same thing would also happen with an eroded water pump impeller.

It's probably easier to back-flush the heater core loop than pull a water pump though.

 

Alright, I will try that this weekend. Which is the inlet on the heater core? I am assuming the inboard one. Also, do I need to pull the hose from the core itself or can I pull it from another point to flush both the front and back heater cores at the same time? Sorry for so many questions but I have looked for a diagram with no luck. Also, it only has 135K miles so I would hope the pump wasnt erroded but I guess its possible.

 

Well now I have a new problem. I drained the radiator tonight to add cleaner in preparation of doing a flush this weekend. I put water in the bottle after draining and started the engine. I assumed it had filled the radiator. I thought it was kinda quick for 3-3.5 gallons but didn't pay it much attention. I started the engine temp came up about a 1/4 way on the gauge and heat was warm I revved it up to about 2500 and held it there. The air coming out of the vents got hotter and was working good. I let it go to idle and the air cooled down. Brought it back up to 2500 and held it there. After 30 seconds or so the engine shutdown on its own. Temp was still at 1/4 way up the gauge. I let her cool down for 20 minutes or so and she started back up fine but I shut it down and heard a hissing. It overheated I guess. I got my wife to start it and shut it down for me and it sounded as if the hissing was coming from the heater core hose inlet. I felt the hose and it was empty. The bottle I filled still had water in it and hadn't dropped much. Do I have to have the cap on the bottle for it to circulate cooling water? I didn't!!!! Also if my water pump has eroded, would it no be pulling water from the bottle/ radiator and circulating it? Thanks for all your help.