Heater not getting hot?

Tiny
ADAMCLEV
  • MEMBER
  • 1999 FORD EXPLORER
  • 4.0L
  • AWD
  • AUTOMATIC
  • 122,000 MILES
So I replaced the thermostat in my 99 ford explorer because the heat wasn't getting hot just warm. The hoses going into the firewall top was hotter than lower. Since I've replaced the thermostat now there is absolutely no heat at all blower works AC works but the heat just blows cold air not even warm like it was b4. I have no idea where to go now. The flap behind the glove box opens when I put it on AC and closes when put to heat. Any help would be greatly appreciated.
Monday, December 9th, 2013 AT 6:43 AM

39 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 34,079 POSTS
Does the engine overheat now? If it does, there's most likely an air pocket under the thermostat that has to be bled out. If there's no bleeder screw, look for a threaded plug or a sensor on or near the thermostat housing that can be unscrewed. This video can help us fix it.

and this guide and video can help if its not a thermostat.

https://www.2carpros.com/articles/car-heater-not-working

and

https://youtu.be/SNRb6pSwYuU

Please run down this guide and report back.

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Monday, December 9th, 2013 AT 7:31 AM
Tiny
ADAMCLEV
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No the engine doesn't over heat. In fact the temperature gauge is only about 1/4 if the way up. It's always been that way which kind of led me to thermostat.
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Monday, December 9th, 2013 AT 9:21 AM
Tiny
ADAMCLEV
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Also when I first turn the heat on I get Agee second burst of warm air.
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Monday, December 9th, 2013 AT 9:58 AM
Tiny
CARADIODOC
  • MECHANIC
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Feel the heater hoses after the engine has warmed up. They should be too hot to hold onto for very long. If they are, you might suspect a problem with the actuator on the heater box. Ford has had a lot of trouble with them on the Rangers in the mid to late '90s. I don't know if the other models use the same type.

If the hoses are not as hot as the radiator hoses, look for a water control valve inline with one of the heater hoses and be sure that is opening fully.
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Monday, December 9th, 2013 AT 10:01 AM
Tiny
ADAMCLEV
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Yes before I changed the thermostat the upper House got slot warmer than the lower hence another reason I leaned toward thermostat. Now neither houses are getting warm. I hooked up garden hose and flushed then still n No heat and the houses aren't warning to at all near the firewall
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Monday, December 9th, 2013 AT 3:30 PM
Tiny
CARADIODOC
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Are you talking about the upper and lower radiator hoses? If those aren't hot, there's something wrong with the new thermostat. They don't fail very often so I'd look for it's not seated and sealing properly in the housing, or someone pried it open and it is stuck there. That just involves making sure the pin in the center is not popped out of position.
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Monday, December 9th, 2013 AT 3:41 PM
Tiny
ADAMCLEV
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Did some more "testing" when I have vehicle idling or while driving and give it more gas "idle it up" the heat seems to kick in
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Tuesday, December 10th, 2013 AT 2:44 PM
Tiny
CARADIODOC
  • MECHANIC
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There's two common causes of that. If the engine is not running hotter than normal, the coolant level is low and there's an air pocket in the engine. If the engine IS running hotter than normal, look for a slipping water pump belt, especially on engines where the timing belt runs the water pump.
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Tuesday, December 10th, 2013 AT 2:58 PM
Tiny
ADAMCLEV
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Yes the engine is running VERY cool ( so the gauge says.) How would I go about bleeding it I've looked oblong and it says there's a bleeder valve next to the thermostat housing ( there isn't) hopefully that is the issue. Thank you very much for you responses they have help and probably saved me hundreds of diagnostic parts and labor.
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Tuesday, December 10th, 2013 AT 4:18 PM
Tiny
CARADIODOC
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Sorry to leave you hanging. Had another computer melt-down, but after a few hours, it's up and running for who-knows-how-long.

I don't think bleeding is the issue. Thermostats don't open in response to hot air. They must be hit with hot liquid. For that reason, an air pocket will result in overheating. You have the opposite. Use a special hose pinch-off pliers or fashion something with a pair of wood blocks that you can use to pinch the upper radiator hose. That is doing the same thing as the thermostat does. If you see the temperature come up after a few minutes, suspect your new thermostat.
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Wednesday, December 11th, 2013 AT 4:02 AM
Tiny
ADAMCLEV
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Thanks a lot! I'll try that as soon as I get out of work.
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Wednesday, December 11th, 2013 AT 6:25 AM
Tiny
ADAMCLEV
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No doesn't overheat (unless didn't leave it clamped long enough) when I first turn the heat on I get a burst of heat then just very low heat. When I keep the Rpms up in neutral or park it has good heat
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Friday, December 13th, 2013 AT 12:15 PM
Tiny
CARADIODOC
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Sounds like you're not getting enough volume through the heater core, but not because it's plugged. If it was plugged, you wouldn't get higher temperatures when raising engine speed. The initial burst of hot air says the hot coolant did circulate through the heater core but it's cooling down right after you turn on the fan and draw cold air through it. Is there a water control valve inline with one of the heater hoses? I hope I didn't ask that already. I'm working with a few other people with heating problems, and I can't go back to page 1 of this conversation to reread it.
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Friday, December 13th, 2013 AT 1:46 PM
Tiny
ADAMCLEV
  • MEMBER
  • 30 POSTS
I don't see a water control line next to either house by the firewall. However I did notice something else as I was shoveling the foot of snow we got here I moved my truck and didn't turn the heat on (must have forgot) either way I decided to check the 2 houses going into the firewall and both were actually very hot usual just the upper is. So like a optimist in thought wrote it fixed itself. No such luck I hoped in the truck hit the vent floor option button heat for about 20 second then. Nothing also the lower heater house by the firewall cooled right down. Don't know if that gives any obvious options or not but figured I'd toss that observation out there. Also did I mention it has the digital heat controls I've even tried turning the"max ac" on and setting temp to 90. No luck trying everything not to have to bring it to a mechanic out here since I just moved about 2 hours away from my home town and don't know any. But with a 4 month old and a 5 year old heat is beginning to be needed sooner than later it was a blistering 13* today.
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Sunday, December 15th, 2013 AT 3:36 PM
Tiny
CARADIODOC
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Everything you've said points to insufficient volume through the heater core. The second heater hose really won't be noticeably cooler than the feed hose. When it is, it's because too little hot coolant is going through the heater core, and what is getting through has plenty of time to be cooled down. I think there has to be a restriction somewhere. As I recall, you said there's a new heater core in there already. Still, I would disconnect both hoses, then run water through the heater core, then both hoses, with a garden hose. The water must flow easily through each hose without building pressure and spitting back as long as the radiator cap is off. If you find the water doesn't flow through one hose, check if it's hooked to a metal pipe pressed into the intake manifold. Those are made of very thin steel, and when they corrode, a part of it could flop over and block coolant flow.
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Sunday, December 15th, 2013 AT 5:46 PM
Tiny
ADAMCLEV
  • MEMBER
  • 30 POSTS
  • 1999 FORD EXPLORER
  • 120,000 MILES
So my 1999 ford explorer limited six cylinder 4, 0 SOH has no heat. Well it gets sorta warm. The AC works great. But with winter time in central New York and a four month old. New born and a five year old heat is a necessity. I've changed the thermostat hoping that would be it. The temperature gauge in the vehicle also stays real low not even close to half way between c and h so I'm guessing that has something to do with it. Any help would be greatly appreciated. This site and everyone on here has been a tremendous help with any issues I've had. So thank you all.
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Friday, December 28th, 2018 AT 10:30 AM (Merged)
Tiny
MHPAUTOS
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Your thermostat may be faulty (stuck open all the time) just because it is new better re check it, also with the engine as hot as it gets feel that both heater hoses are hot to touch, if not you may have a blocked heater core, start here.
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Friday, December 28th, 2018 AT 10:30 AM (Merged)
Tiny
ADAMCLEV
  • MEMBER
  • 30 POSTS
I had a thoughtnthe thermostat may be faulty. (Hopefully) will check the hoses as well. The hoses your talking about bare the ones near the firewall correct? I've heard the heater core is an bear to change in the truck. (Taking apart whole dash possibly?) Thank you for your response will post back when I have checked theses option provided.
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Friday, December 28th, 2018 AT 10:30 AM (Merged)
Tiny
MHPAUTOS
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Yes check the 2 hoses entering the fire wall, these are the heater hoses.
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Friday, December 28th, 2018 AT 10:30 AM (Merged)
Tiny
ADAMCLEV
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Upper heater hose is quitenanbit hotter than lower.
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Friday, December 28th, 2018 AT 10:30 AM (Merged)

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