My 2003 mountaineer 4.6L has front and rear heat. The issue is the heat in the front is barely warm and the heat in the back is poor. I have replaced the blend doors front and back and I'm sure they work as I can go from cold to barely warm and back again when I change the temperature setting.

I can feel hot fluid going from the engine to the front heater core and also down under the vehicle to the rear when the vehicle is warm. The return on the front is almost cold - so heat is being given up by the heater core in front, but it seems to me that if the return is almost cold, there's not enough hot coolant delivery. The overall heat is very poor in the cabin.

The coolant temperature gauge is steady and just below 1/2 with no erratic movements. I flushed the front heater core a couple years ago. Coolant has also been flushed last year.

Does anyone have any suggestions or thoughts? I know that the heat is underpowered in this vehicle, but it's a far cry from when it was new. Thanks.

 

Use an IR gun and take some temp measurements, sounds like you have low engine temp and limited flow to the heater cores... Philip

 

I have the same exact problems and am also searching for an answer. I'm thinking the heater core may be plugged, but I'm also not sure if there is a control valve in line somewhere that isn't functioning properly. If I find an answer I'll let you know.

 

THe return hose is cold so you think that the heater is pulling all the heat out of the coolant.. One thought is that there is not enought coolant flow thru the radiator so the heat pulled out of the coolant is minimal... I agree with the guys, you need to check heater pluggage, good flow, and make sure the water is up to 190 degrees. If the thermostat is 15- 20 degrees low, that will effect the heat.
---Connecting a garden hose to the heater and blowing thru it out to a bucket is a good way to check for pluggage. I have heard guys talk about water pump impeller wearing out, but i personally have not seen that.

 

Ok, I finally had a day warm enough the water wouldn't freeze to flush the heater core.
I didn't really see any nasty looking stuff but still did a complete flush of the heater core anyhow.It didn't seem to make much difference that I could tell so I crank the heat all the way up and it throw some heat. I started looking at other options and what I did find was the cabin temp sensor was covered in dust. I blew it out good with the air hose and then the heat starting working properly. I wouldn't have thought that would effect it but it must somehow as all is functioning properly now. Anyone have an explanation as to how that would cause the problem?

 

Interesting timing. I didn't have any concerns with the heat in my 2004 Aviator, but last weekend when detailing the instrument cluster I noticed that my cabin temp sensor was furry and grey. I pulled the sensor out of the dash so I could clean both sides of it. I got it looking like new, put it all back together. I drove the Aviator every day last week for a variety of short and longer trips, no change in the function of the heater. The only change I was thinking might happen would be a faster response to the cabin temperature as there would be less "insulation" on the sensor that might slow the response time. But I didn't notice a difference if there was one. So, no, I don't have an explanation as to why that would make a difference, unless your cleaning of the sensor just happened to correlate to the air finally burping it's way out of your cooling system so the heater core was getting a full flow of hot coolant.

Did cleaning the sensor cause the rear heat to seem better as well? If so, I'd be leaning more toward the coincidence of air getting purged at the same time since I don't think the cabin temp sensor had an impact on the rear HVAC.

-Rod

 

i agree with shorod.

 

Completely open the glove box, past the stops. Look up in the vent system into the grate. That is where you draw outside air from. There is a vaccum operated door in there. I likes to break off. If it did you will get a lot of cold air all the time...well except in the summer. If the door fell over the fan you will get lousy air flow too. If this happened to you, the best method to fix it is to pull the blower, hold the door in place, use a drill and extension with self tappers and screw it shut....if you need outside air open a window.

 

I'm having a heating issue as well but it is not constant. I already know I have a blend door issue but even when the blend door is set to the position for heat I have my problem. The problem I have is the heat is not constant. At low speeds I have cool and sometimes even cold air. The faster I go or the longer I maintain a constant speed the heat is warm to hot. If I am rolling along on the highway for a period of time it's nice and warm in the cab but if I hit traffic or slow down in the city I loose my heat. As I said earlier, I have the clicking noise going on with the blend door but I can reach in through the glove box and flip the little lever to close it and it stays for several days. It has me confused that one minute I have heat and then the next I don't without ever changing any settings. Any thoughts you guys have would be greatly appreciated! Thanks in advance!

 

It sounds to me like there is air in your cooling system. It could be due to an air pocket from recent maintenance or it could mean your coolant level is low due to a leak. The heater core is rather high in the cooling system and air will rise to the top of the system.

If you confirm the coolant level is not low and you're unable to burp air out of the system, try back-flushing the heater core. There are kits that you can install to make this easier but if you have an old garden hose and some hose clamps you can make your own flush kit. If back flushing the heater core seems to work, you should really consider flushing the entire cooling system, replacing the hoses that are likely past due to be replaced, and replacing or recycling the coolant. There are cooling system recycling systems that will accomplish the flush and recycle portion for you in one step.

If none of that seems to be the issue, then the issue might be a worn water pump. Some other Ford products have had issues with water pump impellers dissolving due to galvanic corrosion (poor cooling system grounding). That's almost always accompanied by dark, dirty coolant.

-Rod

 

Rod,
Thanks for the help! You were dead on and my coolant was low as well as I also found the front cross member is wet with antifreeze so I must have a leak. After topping the coolant off I now have awesome heat. Now I just have to find where I am loosing the coolant. Not sure what to call it but the pan or shield on the underside of the radiator is damp all the way across and it appears the coolant is making its way right to left and blowing out the drivers side of the shield and back onto the cross member. Do you have any experience changing the radiator on an 05 explorer and if so how difficult? Can the cooling system be pressure tested?
Thanks!

 

I don't have any experience with changing the radiator on the 2005 model year, but I have a service manual for 2005. If you're interested in the applicable section, send me a Private Message with the request, model and model year, and an e-mail address for you that can accept PDFs and I'll send the information your way.

-Rod

 

I rigged the blend door with a zip tie so there is some heat; however, it is not very hot. I removed the thermostat and checked it with a pot of hot water, it reacted at 190 degrees as it should. Since I am still figuring out all that needs to be done to put this truck in great shape, I suppose I should flush the heater core? How difficult is that on an 03 4x4?

 

Take the heater hoses off and connect a garden hose to one and blow out thru the other... OR cut one hose and buy a plastic TEE to put in line. Connect the garden hose and open the radiator drain and remove the fill tank cap. Let if overflow out both holes. The TEE can also be used to burp out any excess air when you refill.

 

If I did a standard coolant system flush, not a power flush, would this accomplish the same thing? or not enough pressure?