Mechanics

HEATING

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.
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AdamClev
December 9, 2013.



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.

Caradiodoc
Dec 9, 2013.
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.

Tiny
AdamClev
Dec 9, 2013.
Also when I first turn the heat on I get Agee second burst of warm air.

Tiny
AdamClev
Dec 9, 2013.
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.

Caradiodoc
Dec 9, 2013.
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

Tiny
AdamClev
Dec 9, 2013.
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.

Caradiodoc
Dec 9, 2013.
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

Tiny
AdamClev
Dec 10, 2013.
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.

Caradiodoc
Dec 10, 2013.
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.

Tiny
AdamClev
Dec 10, 2013.
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.

Caradiodoc
Dec 11, 2013.
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