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Heat is Warm but not Hot

massacre

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‘19 Nautilus
Hello, I have been searching the threads here, and I think I might need to ask a question-

I replaced radiator, water pump, heads, new rad hoses a year or two ago. Also installed a new stant thermostat, new temp sensors.
Temp gauge always read low after this, but the heat was still hot.
Noticed reduced airflow from the blower motor, so I cleaned out the heater box which was plugged with pine needles/mouse nest debris/leaves. Vacuumed out the crap, blew the heater core out with compressed air and put everything back together.
That resulted in a huge improvement in airflow through the vents, and a slight improvement in how hot the heat is, but it’s still not as hot as it should be. Coolant is 50/50 mix and no leaks. Level is good.
I grounded the gauge and the gauge is working correctly. The hoses do get hot. Not sure exactly how hot, but they are definitely not cold.
I am having a hard time figuring out if the heater control valve is working properly.
The vacuum hose that attaches to the heater control valve, seems to go to the part of the intake tract that attaches to the intake airbox, and also is attached to the heat riser from the exhaust manifold on the passenger side front.
I never reinstalled the heat riser when I put everything back together. I put vacuum to the HCV side of that hose and it doesn’t leak.

So my question is- does that heat riser part of the intake apply vacuum to the HCV? Is this to keep the coolant circulating through the engine to prevent cold air from being blown into the cabin until the engine is warm?

I would like to replace the heater core, since it is original and the truck has about 100k miles. I tried to blow out as much of the heater core as I could through the heater box, but I suspect that it might be blocked with dirt/dust on the airflow side. These heater cores seem really easy to replace compared to other heater cores I have replaced. While I’m doing that I figure replacing the HCV is a good idea.
Will also replace the thermostat since the gauge is reading low.
My concern is that I don’t want to replace these parts and end up back where I am now.
Plan is to remove the cover to the heater core and see if the heater core is actually getting hot or not.

Is the lack of the heat riser causing my issue?

Any advice would be greatly appreciated
Thanks!
 


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massacre

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I will drop some coolant and remove the temp sensor and see if the sensor is actually working.
 




MakinJeepsWeep!

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What temp tstat did you put in it? If its 5.0 should be 192 or 190 will be fine. Also as i have seen in a mustang and a mercury even with the same temp tstat it threw a engine code, replaced with a motorcraft and no more code, assume they open faster or slower rate. Point being there not all the same. Did you test it when you installed it to make sure it opened at the right temp? some can be bad new and open before or after the set temp.
 




MakinJeepsWeep!

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That valve you talk of only allows hot water to flow through the core, it cuts off the hot water so you dont have heat inside when running the ac. Get the most out of the ac system. As far as i know at least.
 




massacre

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Sorry it’s a 4.0 OHV V6
No codes thrown yet.
it was working fine after install.
Thanks for the info on the HCV. So if it’s hot out, the HCV is supposed to block hot coolant from flowing through the core. Makes sense.
Problem is that it is cold here, not hot.
And if the heat riser is supposed to warm it up, I guess I’m confused on that whole temperature valve situation and how it works? Is it supposed to receive vacuum when it is hot out? Or when it is cold out? Where does it receive vacuum from?
i have some manuals here but none of them get into enough detail.
thanks again for the replies! Much appreciated
 




MakinJeepsWeep!

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Your talking about the valve that is kinda above where your ac coils are above the black box, im starting to think your set up is more like my 3.0 has water lines ran to the TB and to the heater core. That valve is too open when you put it on heat inside the truck. When you turn on heat inside the truck it supplies vacuum to that valve to open it so that water can pass through the heater core much the same way your tstat does water and your radiator. Same exact idea just you operate one not the tstat and the heater core itself is nothing more than a radiator in the cab that you get heat from.

It being a 4.0 of that year im unsure of the O.E. temp but in my 06 4.0 its a 192 stat as well. The gauge not coming up to somewhere close to middle makes me think its too cold of a tstat. In the owners manual it states that the needle should come up to the half way point on a completly warmed up engine, mine in my 96 5.0 hover just a bit below middle i can try and post a pic if you would like. Also not over heating does not mean it is correct. What is your fuel mileage like, if the engine is not getting to a set temp the computer will run the truck in a slightly rich state to get it to warm up.

I hope this helps you buddy ill try and answer any other questions you have if i can
 




Mighty Quinn

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Hello, I have been searching the threads here, and I think I might need to ask a question-

I replaced radiator, water pump, heads, new rad hoses a year or two ago. Also installed a new stant thermostat, new temp sensors.
Temp gauge always read low after this, but the heat was still hot.
Noticed reduced airflow from the blower motor, so I cleaned out the heater box which was plugged with pine needles/mouse nest debris/leaves. Vacuumed out the crap, blew the heater core out with compressed air and put everything back together.
That resulted in a huge improvement in airflow through the vents, and a slight improvement in how hot the heat is, but it’s still not as hot as it should be. Coolant is 50/50 mix and no leaks. Level is good.
I grounded the gauge and the gauge is working correctly. The hoses do get hot. Not sure exactly how hot, but they are definitely not cold.
I am having a hard time figuring out if the heater control valve is working properly.
The vacuum hose that attaches to the heater control valve, seems to go to the part of the intake tract that attaches to the intake airbox, and also is attached to the heat riser from the exhaust manifold on the passenger side front.
I never reinstalled the heat riser when I put everything back together. I put vacuum to the HCV side of that hose and it doesn’t leak.

So my question is- does that heat riser part of the intake apply vacuum to the HCV? Is this to keep the coolant circulating through the engine to prevent cold air from being blown into the cabin until the engine is warm?

I would like to replace the heater core, since it is original and the truck has about 100k miles. I tried to blow out as much of the heater core as I could through the heater box, but I suspect that it might be blocked with dirt/dust on the airflow side. These heater cores seem really easy to replace compared to other heater cores I have replaced. While I’m doing that I figure replacing the HCV is a good idea.
Will also replace the thermostat since the gauge is reading low.
My concern is that I don’t want to replace these parts and end up back where I am now.
Plan is to remove the cover to the heater core and see if the heater core is actually getting hot or not.

Is the lack of the heat riser causing my issue?

Any advice would be greatly appreciated
Thanks!
I have a '96 exp that had same problem. ended up being the blend door. it's a big butterfly valve under the glove box in the duct. it open and closes when you turn the blue to red knob on the dash, ( next to the fan knob). The hinge pin broke off on mine. there is a good thread on this site on how to fix it. (if you can find it)
 




massacre

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Thanks so much for the helpful responses!
I need to do some more research but it seems like it might be a combination of a few things.
i might just replace HC and HCV and thermostat. Reasonably cheap parts, I have the time to do it, and it would hopefully eliminate problems since they are 25 yr old parts.
Thermostat is a bummer since it is relatively new.

Does anyone have any part #s for the heater core hoses? Or am I just buying bulk hose and cutting it to fit?
is it 5/8” heater hose? Or 3/4”?
thanks so much
 




MakinJeepsWeep!

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I usually just buy bulk heater hose most places you can just buy it by the foot, If i remember right it is 5/8 i cut a piece off and take it with me to compare. Look at it this way, If all that doesnt fix it all that is left is the blend door and the controls to it.
 




massacre

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Thank you!
I did some more investigating today.
Removed the glove box and the ashtray insert.
I can see the cable going from the temp control panel to the top of the blend door. Sprayed a little bit of lube on the cable. Removed the heater core cover to put hand on heater core to see if it was warm. It was. Then I put a skinny flashlight behind the heater core to see if I could see through it. It does not appear to be blocked as far as airflow. The heater core actually looks like it’s in great shape to be honest.
visually tested/inspected the blend door, it functions properly and seems to be moving through all of its range of motion. Door does not seem to be blocked by any debris but I might stick a mirror up there to make sure.
Tested with blower on and the blend door seems to be working properly.

So I guess next move is a new thermostat. I may replace the blower motor as well.
It seems the heater core is getting ”warm” but not hot. So coolant flow is not blocked, airflow is not blocked, HCV is fine. Blend door and the controls are working.
The air box was so stuffed with debris that I’m wondering if the blower motor was working hard. It made some noise when I first bought the truck but went away after a while. Now i am getting electrical burning smell and motor wires are kinda hot. So might replace motor and resistor since I am sure they are original.

I’ll get some parts tomorrow
 




BKennedy

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Its possible the heater control valve is not fully opening. The heater hose entering the firewall should be as hot as the hose going to the valve when the heater is on. You can test it by bypassing it completely. I actually have two pieces of tube that fit inside the hoses so I can bypass it because I had one fall apart in my garage. I don't want to be 50 miles from a paved road and have that happen again. If you get a new valve, make sure its orientated the same as the OEM part. I bought one that was plumbed the opposite as the OEM part so it would not work. Valve came apart on my daughter's 2010 Ranger a few weeks ago and dumped all the coolant out in a few minutes but luckily she is well trained and pulled over. New valve from Napa was a exact replacement, and identical to the one in my 1994 Explorer.
 




massacre

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Thanks!
Well all of the hoses seem to be the same temp- warm, but not hot as well as the heater core.
Combine that with the gauge reading cold all the time, plus the fact that I tested the gauge and it is working, is pointing to a bad thermostat.
 








massacre

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Ordered a new T stat & gasket, new blower motor and new resistor from Tasca Ford. Parts should be here next week.
If that doesn’t solve it, I can go the heater core/HCV route but honestly I think that stuff is fine.
We’ll see lol
 




TheDudeAbidez

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The heater core can look ok on the outside, but easily be clogged inside. Also, the HCV is a common culprit on the first gen X. Remove the cover plate at bottom of heater box in pass floorboard, and replace the heater core. Then pop in a new HCV. Then make sure you burp the system multiple times after refill to get all of the air out. That's just my opinion, but it sounds like darn near everything else is new....so that's where I would start.
 




MakinJeepsWeep!

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If all the hoses are the same temp i doubt it is blocked. I guess half the core could be blocked but thats alot of debris in there and would think there would be other issues if was that bad. Im still going with too cold a tstat, What temp tstat did you order?
 




massacre

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Thought I ordered a stock T stat
it used to warm up on the gauge fine but has not being doing that lately (showing cold)
Went with stant last time but goin mocraft this time
we’ll see lol
 




massacre

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The heater core can look ok on the outside, but easily be clogged inside. Also, the HCV is a common culprit on the first gen X. Remove the cover plate at bottom of heater box in pass floorboard, and replace the heater core. Then pop in a new HCV. Then make sure you burp the system multiple times after refill to get all of the air out. That's just my opinion, but it sounds like darn near everything else is new....so that's where I would start.

Well the heater core is as warm as everything else so I’m guessing it’s not blocked.
I can always go back later and replace the HC and HCV since it’s so easy
Had no idea it was this easy on these trucks
 




TheDudeAbidez

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It may not be an issue...I just know I tried flushing and backflushing the HC in my 94. Not much helped until I replaced with a new unit. Sounds like you're on the right track though. Keep posting up your findings, as the project progresses.
 


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BKennedy

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If you are replacing the heater control valve, go ahead and backflush the heater core while the hoses are disconnected. Did that to my daughter's 2010 Ranger and some gunk came out.
 




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