Baffled by Heater Issue...2001 Explorer Sport

[CreepingDeathS1]

Hello, I have been having a heater issue and have reviewed most of the threads Ive seen regarding this but still not having any luck so I thought Id post.
I have a 2001 2 door sport 4wd that i bought last oct. heater and AC worked when I bought it. During a trip in December I noticed my heater started blowing colder. I pulled over to investigate and discovered radiator was leaking and level had gotten low. I refilled it and the heater went back to working, just topped it off a couple more times to get through the trip and return home. ad heat the whole time despite the leak as long as I kept the coolant level full.

At home I I also have a low mileage 1997 LTD 4 door that my brother and I use for parts. It had a crank failure at 60K miles or so. This explorer had a perfect radiator so I swapped it into the 2001. Leak solved but heater was luke warm thereafter. I made sure to burp system a couple of different times, still Luke warm. Lived with it the rest of the winter.

Took another run at fixing it this fall, thought I had it fixed but today is the first real cold day and surprise no heat. Here's the stuff Ive done or checked: Replaced the radiator. Replaced the Radiator cap. Replaced the Heat control valve. Replaced the thermostat. verified control valve is operating properly and all vacuum lines are attached and working. Flushed heater core (water went right through it and came back out with no disruption or rust/debris). Heater blower motor works fine. I have not taken the actuator off or tried to get at the blend door, however when I move the temperature control from cold to hot it does change the temp and seems to work as does the AC in hot weather. Hot is only mildly warm but you can tell there is a temperature change happening and it seems like it is working especially when you have the AC on and move it over to hot. plus it all worked fine prior to me replacing the radiator. I have noticed that the motor never get overly hot, no matter how long it runs or even if it sits and idles for a long time. After sitting and running it seems like it will build a tiny bit more heat and when I turn the fan motor on it seems slightly warmer for 10 seconds or so then gets colder. I can touch all the hoses under the hood..most of them are warm or hot but none so hot that I cant hold on to them barehanded. The hottest one seems to be the inlet side of the heater core when the control valve is open. It also doesnt seem like it has a tremendous amount of pressure. I can usually take the radiator cap off at any time with only minimal pressure or spraying, despite just putting a new cap on it. Overflow is working properly and I cant find any leaks anywhere...it seems like the closed system is truly closed. At this point I am baffled. Anyone have any ideas or experienced anything like this? Many Thanks! Steve

 

[410Fortune]

I usually suspect blend door issue with a Gen II that wont switch from cold to hot
Lets do some brainstorming, thinking out loud here


You said the truck never really warms up or builds pressure in the cooling system, but you replace the thermostat. You should check the thermostat function and water temps
Do you have a code scanner?
Do you have one of those laser temp reader that will tell you the temp of an object?

I know you said it seems to switch from cool to hot, but it never really gets "hot" that is likely because the bled door is still mixing it with cold air?
Does the system switch from defroster to the feet location?

Next I would plan to have a look at the bled door actuator, I know I know its a PITA to remove, but can be done. I use a really low profile 1/4" drive and short socket
You can practice on that 97 for parts?

Have a look at the end of the blend door axle (the part the actuator turns) either w the camera on your cell phone or a dental mirror
Then see if you can open close the bled door manually with the actuator off

 

[CreepingDeathS1]

I usually suspect blend door issue with a Gen II that wont switch from cold to hot
Lets do some brainstorming, thinking out loud here


You said the truck never really warms up or builds pressure in the cooling system, but you replace the thermostat. You should check the thermostat function and water temps
Do you have a code scanner?
Do you have one of those laser temp reader that will tell you the temp of an object?

I know you said it seems to switch from cool to hot, but it never really gets "hot" that is likely because the bled door is still mixing it with cold air?
Does the system switch from defroster to the feet location?

Next I would plan to have a look at the bled door actuator, I know I know its a PITA to remove, but can be done. I use a really low profile 1/4" drive and short socket
You can practice on that 97 for parts?

Have a look at the end of the blend door axle (the part the actuator turns) either w the camera on your cell phone or a dental mirror
Then see if you can open close the bled door manually with the actuator off

Thanks for the response! I have a code scanner but not one that shows the live data. Maybe Ill go pick one of those up today.
Temp control definitely seems to work. I can turn the ac on with the control on cold and I have ice cold air. If I move it to hot it stops being cold.
Heater control knob works well. If its set to blow on the floor it does. on the panel it does. both..yep. All the positions work fine.
I can absolutely practice on the 97. Ive got most of its dash torn apart at this point anyway. It lives outside though.
Ill give that blend door a try in the coming days for sure. I really dont think its the problem, but I havent physically verified that.
The only other thing that occured to me today is the radiator itself. Advance Auto has a different part number listed for the radiator on a 97 vs my 01. Ive never checked that before because they look identical but it seems one has 1" 1 core and the other has 2" 2 core. I would think that probably doesnt matter since the thermostat would control the heat either way...unless maybe the 2" 2 row core is so efficient in its cooling that it never gets hot....?

I guess live data scanner or temp gun might prove if that is true or not.

 

[CreepingDeathS1]

Well it is not the blend door or the actuator. I removed the actuator and tested it and also manually moved the blend door. It’s all good.

Its also not the radiator or thermostat. I decided to buy a new radiator just In case since they had different part numbers. Didn’t change heat situation at all. Watched live data to see thermostat opening at 192 or so...engine is normal operating temp.

I again flushed the heater core as it’s lines are still not real hot. Water goes in one side and comes out the other side clear. It still seemed like that return hose was not hot enough so I even took that hose off while the engine was running with the heater on. Got Antifreeze ran out as soon as I did. I am totally baffled....

 

[Mbrooks420]

Does engine rpm affect the heat output at all?

 

[koda2000]

My first thought was that the blend door or actuator was not working properly. As you say it is, my next thought is the thermostat is not working properly. It's not unheard of to get a defective t-stat. You can remove it and place it in hot water to see if it's opening/closing when it's supposed to. Use a meat thermometer to measure the water's temp. You should have installed a t-stat the rated to open at 192-195F. You can't tell much from the temp gauge on your dash, but the needle should stay in about the center of its sweep at normal operating temp. An inexpensive digital laser temp tool would be a big help in seeing what the actual coolant temp is at various engine locations.

 

[CreepingDeathS1]

My first thought was that the blend door or actuator was not working properly. As you say it is, my next thought is the thermostat is not working properly. It's not unheard of to get a defective t-stat. You can remove it and place it in hot water to see if it's opening/closing when it's supposed to. Use a meat thermometer to measure the water's temp. You should have installed a t-stat the rated to open at 192-195F. You can't tell much from the temp gauge on your dash, but the needle should stay in about the center of its sweep at normal operating temp. An inexpensive digital laser temp tool would be a big help in seeing what the actual coolant temp is at various engine locations.

No engine rpm doesn’t impact anything. Thermostat is working for sure. I changed it again too just in case but you can see it working with the scanner live data as well as just by feel of the hose and watching the temp gauge. It’s opening right round 192.

 

[danno2944]

I went and looked at the diagrams and this really makes no sense to me? You have investigated everything, only thing you haven't mention is the evaporator.

Don't know much about it, just adding my two cents, seems like the next logical place to investigate to me.

 

[Mbrooks420]

I don’t think the evaporator has anything to do with heat, that’s AC only.

Does your temp gauge fluctuate while driving?

 

[CreepingDeathS1]

I don’t think the evaporator has anything to do with heat, that’s AC only.

Does your temp gauge fluctuate while driving?

Temp gauge works like normal. Doesn’t fluctuate any more than normal

I’m going to try draining everything and flushing it all again....

 

[koda2000]

If engine is getting up to temp, the t-stat is opening at 192 degrees, the heater control valve is open (which is it's normal position) and the heater core isn't clogged hot water should be getting into the heater core and the blower blows air through the heater core you should be getting plenty of heat if the blend door is opening.

You say all these things have tested out okay so I see no reason you shouldn't be getting heat. I asked you what setting you were using on the HVAC controls, because if you set if to MAX A/C the A/C will cool down the temp of the heat you get and the heater control valve closes in the MAX A/C setting, which stops hot water from getting into the heater core.

When operating is one heater hose at the firewall very hot and the other not quite so hot? That would indicate that you're getting normal flow through the heater core.

 

[Mbrooks420]

I’d try jacking up the drivers side as high as my jack would, and running it up to warm with the cap off.

 

[CreepingDeathS1]

So flushing everything again showed me an issue but I still don’t really understand.

I drained everything. I used hose to flush new radiator. I took the heater hoses off the core and again flushed the core. No issues with any of that. I closed the radiator drain and refilled the radiator with water then took the heater hoses which were still disconnected and used the hose to flush water through them. Each time on each hose it came out of the open radiator cap. Continued to do that with each hose till water ran clear then drained system again and refilled with 50/50 mix. Started car, burped system the. Replaced rad cap and let it get hot. Still no heat in the vehicle.
Heater hoses on the core...one was really hot the other not as hot. Which is correct I think.
Decided to switch the hoses on the core even though I knew they were correct thought what the hell. No change no heat. So I decided to switch them back to their proper places....this time I decided I would do it while the car was running. I have video but not sure how to upload it. Took both hoses off the core with the car running and once I held them up coolant stopped coming out of them completely!!!! With the car running! So there must be some type of blockage or partial blockage from the inlet to the inlet side of the core. But it did bubble back and over flow the radiator when I flushed it with the hose. So maybe it’s only when it’s running? Maybe something to do with the water pump or maybe all the stop leak the previous owner put in the radiator has broke loose and is blocking the inlet somewhere...not sure but couldn’t work on it anymore today.

 

[Macgiobuin]

I had a Taurus that had similar problem. It turned out that the water pump impeller had an electrolysis problem. The body of the water pump was plastic and caused a spinning electrolysis voltage which caused the stamped steel water pump impeller fins to pit and deteriorate, until there was only a flat disc spinning. So none of the coolant was actually circulating. Worth a look.

 

[koda2000]

I had a Taurus that had similar problem. It turned out that the water pump impeller had an electrolysis problem. The body of the water pump was plastic and caused a spinning electrolysis voltage which caused the stamped steel water pump impeller fins to pit and deteriorate, until there was only a flat disc spinning. So none of the coolant was actually circulating. Worth a look.

I had the same thought, but because the engine wasn't over heating I wondered if that could be the problem.

 

[Mbrooks420]

Typically a worn impeller will cause low speed overheating, and heat will increase with RPM since it’d Move a better volume.

Electrolysis is usually caused by bad bad grounding of the motor, coupled with worn out coolant. If your coolant is fresh, it should never be an issue, since the anti-corrosive additives keep the dissimilar metals from fighting.

 

[410Fortune]

try soaking the heater core in CLR then backflush?


Maybe bypass the vacuum actuated heater valve just for testing?

Have you taken the blower motor out to clean the leaves out of the heater box?

What a PITA!!

 

[masospaghetti]

Maybe check the flow from the heater hose into the core by running the engine (briefly) with the hose disconnected? Unless there's a bunch of air in there, you should be getting heat.

I just had this problem with a bad, collapsed overflow hose and a small leak at the water pump, once the coolant level dropped a bit the amount of heat from the vents would decrease rapidly.

When you take the radiator cap off, is the system full?