1999 Ford Explorer 4.0 SOHC heat warm not hot | Ford Explorer Forums - Serious Explorations

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1999 Ford Explorer 4.0 SOHC heat warm not hot

Lee's Automotive

Git-R-Done
Elite Explorer
Joined
September 23, 2020
Messages
1,558
Reaction score
2,147
Location
United States
City, State
Alabama
Year, Model & Trim Level
99 Explorer XLT 4.0 SOHC
Hello everyone so I'm currently trying to figure out a heating issue in my explorer last winter I replaced the water pump, heater control valve, thermostat, upper and lower radiator hose, bypass hose, aluminum thermostat housing, and I flushed the entire cooling system out with a bottle of prestone radiator flush I also back flushed the heater core with a water hose and cleaning vinegar but my heat will not get hotter than 115F at the vents and at 2k rpm it gets to 120F blend door is fine and the heater control valve is opening all the way but for some reason I can't get the heat to get hotter and I really don't want to pull the dash especially in the cold and I really need this fixed because we are expecting a brutally cold winter here with temps as low as 8F also those temps at the vents are with a 47F ambient temp and as the temps drop outside it seems like the heat is less and less warm engine temp is staying around 85C and 90C the water pump heater control valve and thermostat is all ford OEM and the hoses are Dayco if anyone has a suggestion on what I can use in the heater core to flush it or if I'm missing something please let me know
 



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Whenever I read no heat, I always question coolant level. Especially when higher rpms give more heat .

Radiator should be full, cold engine running with hot and floor selected. It helps a ton to raise the front, or parked on an uphill angle. Don't assume if reservoir looks good, the radiator is full.

Another possibility is debris in the HVAC box blocking airflow through the heater core. Leaves, on ne needles, mouse nest, all are possible. I think it's relatively easy to remove the blower housing and take a look.
 






Whenever I read no heat, I always question coolant level. Especially when higher rpms give more heat .

Radiator should be full, cold engine running with hot and floor selected. Don't assume if reservoir looks good, the radiator is full.

Another possibility is debris in the HVAC box blocking airflow through the heater core. Leaves, on ne needles, mouse nest, all are possible. I think it's relatively easy to remove the blower housing and take a look.
Radiator is full but i haven't checked the blower box i will remove the blower and see what's in there
 






Will i be able to see the heater core by removing the blower or will i only see the evaporator coil?
 






The heater core will be tucked further under dash, the evaporator will be inside the box next to engine. Not good access but you should be able to see in there.
 






The heater core will be tucked further under dash, the evaporator will be inside the box next to engine. Not good access but you should be able to see in there.
Perfect ok ill look in the morning i have great airflow just not hot enough right now it's 110F and it's 37F outside
 






You need too start from the beginning.
You **** the part cannon at it, with poor results.
1. Do you have a code scanner that does live data?
First what the operating temperature of the engine coolant is. If not see step 2.

2. Change the OEM thermostat again. But first test the new thermostat in a pot of boiling water. So you know it actually open. Also make sure it a 195° F part.
3. What the temperature of the coolant going into and out of the heater core? Is it in range?
4. Is it the blend door? Do you have automatic temperature controls?
 






You need too start from the beginning.
You **** the part cannon at it, with poor results.
1. Do you have a code scanner that does live data?
First what the operating temperature of the engine coolant is. If not see step 2.

2. Change the OEM thermostat again. But first test the new thermostat in a pot of boiling water. So you know it actually open. Also make sure it a 195° F part.
3. What the temperature of the coolant going into and out of the heater core? Is it in range?
4. Is it the blend door? Do you have automatic temperature controls?
Um no I didn't fire the parts cannon at it I replaced the water pump and thermostat housing because they were both original and leaking also, I replaced the hoses because they were original the heater control valve was missing so I replaced it also the OEM thermostat is working correctly as I have verified with a scanner with live data coolant temp is 196 also the hoses are too hot to touch when up to operating temp and the blend door works properly and I have the manual controls the only thing I haven't checked is the blower motor box for a rats nest or debris but I will do that tomorrow
 






Um no I didn't fire the parts cannon at it I replaced the water pump and thermostat housing because they were both original and leaking also, I replaced the hoses because they were original the heater control valve was missing so I replaced it also the OEM thermostat is working correctly as I have verified with a scanner with live data coolant temp is 196 also the hoses are too hot to touch when up to operating temp and the blend door works properly and I have the manual controls the only thing I haven't checked is the blower motor box for a rats nest or debris but I will do that tomorrow
You replaced a lot of components.
Water pump
Thermostat
Heater control valve
Hoses
From what You stated , you should have heat. You have 195 °F coolant. The blend door works.
Either you have air in the heater core or no coolant flow thru it. No air flow thru the heater core.
? did you route the heater hoses correctly?
? Is the heater control valve working? My valve uses vacuum.

Can you manually open the heater valve by hand, too see if you get (flow) heat?
 






You replaced a lot of components.
Water pump
Thermostat
Heater control valve
Hoses
From what You stated , you should have heat. You have 195 °F coolant. The blend door works.
Either you have air in the heater core or no coolant flow thru it. No air flow thru the heater core.
? did you route the heater hoses correctly?
? Is the heater control valve working? My valve uses vacuum.

Can you manually open the heater valve by hand, too see if you get (flow) heat?
I have heat but it's definitely not hot as it should be also there is no air in the system and there is flow through the core also yes the hoses are routed correctly and the valve is working I have verified it's fully open with vacuum applied if you read my original message it states I have heat that is around 115F but from what i understand it should be closer to 150F or 160F
 






I have heat but it's definitely not hot as it should be also there is no air in the system and there is flow through the core also yes the hoses are routed correctly and the valve is working I have verified it's fully open with vacuum applied if you read my original message it states I have heat that is around 115F but from what i understand it should be closer to 150F or 160F
On one of my fords. The target heat temperature is 140°F coolant temp. From the Ford service manual.
Then what you state. You don't have a efficient heat exchange at the heater core.
1. Something is restricting the air flow..
2. You have air in the heater core return line. You replaced the hoses. I had a problem with return hose ( not on a explorer). I Purge the return hose and I had heat.
 






On one of my fords. The target heat temperature is 140°F coolant temp. From the Ford service manual.
Then what you state. You don't have a efficient heat exchange at the heater core.
1. Something is restricting the air flow..
2. You have air in the heater core return line. You replaced the hoses. I had a problem with return hose ( not on a explorer). I Purge the return hose and I had heat.
I changed the coolant last winter after a flush it is fully bled out also i believe there is a clog somewhere in the heater core as i have great air flow from the vents
 






Pull hoses from core, stick a cut off garden hose on one core nipple, turn faucet on a tad, see how it flows. Then, turn off water, stick hose on other nipple, do same. It's now back flushed.
 






Pull hoses from core, stick a cut off garden hose on one core nipple, turn faucet on a tad, see how it flows. Then, turn off water, stick hose on other nipple, do same. It's now back flushed.
Will do I did that twice last winter with somewhat better results but I'll do it again later today
 






I following because I'm just curious to see what you find. You have done everything that I would have tried up to this point. At this point I'd be second guessing myself. How did you verify that the blend door works?
 






I following because I'm just curious to see what you find. You have done everything that I would have tried up to this point. At this point I'd be second guessing myself. How did you verify that the blend door works?
A/C is 38F heat is 110F and I can hear the door moving until the door is fully closed
 






So, an update on the weak heat in my 99 explorer I pulled the blower motor and found nothing inside of it there is no debris or rats nest present so I started thinking it could be a bad thermostat so I did a test drive from cold to hot using forscan the lowest temp I seen was 186F and the highest was 194F with an average temp of 192F consistently the ambient temperature was 47F and my heater vent temp on max heat with fan speed 3 was 120F max and 110F-115F average temp the coolant is full in the radiator and it's at the cold fill line in the reservoir, at this point I believe my issue is a plugged heater core but what I find strange is it has perfect flow I have back flushed it 3 times with no change and it has great flow I even used a funnel to pour bottled water in it and it flows perfect I'm not sure what else could cause this other than a partially plugged core if yall have any idea what could be causing this please let me know

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All of these screenshots were made while driving approximately at 55MPH and the total mileage of the "test drive" was 42 miles, at one point of the test drive I did a WOT acceleration from 35MPH to 70MPH with no change in heat temp or engine coolant temp
 






Chemical flush your heater core
I checked my heat comes out at 152f
All the reading s in your pictures are in spec
All the fuel trims are within + - 10% that's great
 



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Chemical flush your heater core
I checked my heat comes out at 152f
All the reading s in your pictures are in spec
All the fuel trims are within + - 10% that's great
Thank's man yep i knew it had to be hotter that 110 lol also could i use a product like evaporust? if not what would you recommend and how would you recommend me do it
 






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