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Temp gauge bouncing and no heat


CynthiaK

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September 23, 2019
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Year, Model & Trim Level
1998 Explorer XLT 4L OHV
Hi,
Yesterday I noticed that my cluster temp gauge was bouncing from normal to C back to 3/4 way to H and then back to normal. It never reached hot.
Now I have no heat. Does the temp sending unit regulate the flow of heat?
I bled the system just now and there were a few small bubbles and then a huge burp but that was all. Still no heat.
If the sending unit does not regulate heat then is it the thermostat, water pump, temp sensor or even heater core?
I have read that if it is the water pump or thermostat, the vehicle should overheat and it isn't.
Also, there are no leaks.
Any and all help is greatly appreciated.
 


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974X4BLACKSPORT

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hudson
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BLACK 1997 SPORT 4 BY 4
1) Make sure the vacuum operated heater control valve is opening properly, it should be located near the firewall in-line with one of the heater hoses going to the heater core. If this valve is closed, hot water will not flow into the heater core (OHV engine). There should be a gray vacuum line connected to the top of the valve, when you turn the temperature control knob to cold in the cabin, vacuum is applied to the servo and the valve closes, and when heat is selected, vacuum supply stops and a spring opens the valve to allow coolant to flow into the heater core.

2) make sure you are full of coolant, and no air is in the system. Air pockets in the cooling system cam make the temp. gauge swing back and forth in short time.

3) make sure your thermostat is not stuck in the "open" position. If the thermostat is stuck open, coolant is always flowing in the radiator and the engine may not warm up enough to provide heat for the cabin.
 








unioncreek

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southeastern WA
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98 Explorer XLT 4x4
Have you checked if the radiator is hot. If it is then then it's most likely the heating valve or something blocking the coolant getting to the heater core.

Bob
 




CynthiaK

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1998 Explorer XLT 4L OHV
Update:
I ran the vehicle for a few minutes and the upper rad hose is hot and the lower hose is warm.
The two hoses that go into the heater core - the top one is cold and the bottom one is hot.
I believe that either the heater core is clogged or the heater control valve is not working.
I did not see the temp gauge bounce during this time.
 




CynthiaK

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Thank-you 974X4BLACKSPORT and unioncreek for your responses!
 




unioncreek

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The bouncing temp gauge is what happens with low coolant or an air lock. Sounds like you took care of that when it burped out the air. What I would try is take the coolant lines off at the heater core and try to back wash the heater core with a garden hose attached. Flush through the one that is cool. I've done this a time or two, sometime it works. I haven't had my Explorer long so I haven't looked at the valve on the heater core. If it's accessible try to manually move the valve and see if that helps.

Bob
 




974X4BLACKSPORT

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BLACK 1997 SPORT 4 BY 4
Regarding the hoses going to the heater core, If one hose is cold and one is hot , this indicates no water is flowing through the heater core. Normally the "IN" hose to the heater core will be the HOT hose, and the "OUT" hose of the heater core should be only warm (having some heat removed in the process of heating the cabin). A cold "EXIT" hose from the heater core means that water is not flowing through the heater core, ... blockage.
 




CynthiaK

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Thank-you you both! I will flush it this afternoon and see what happens.
 




Zeromarine

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City, State
Kamloops B.C
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2002 sport Trac xlt
Sorry to hyjack this thread mine makes great heat in the winter my gauge never goes over what’s in my picture. It will go down a bit from there for a little bit then back to that point. But runs well and makes good hear. Normal for winter I guess. If I remember in the summer it pretty well stays in one spot.

AF995DE0-8526-4A29-AD7A-A8AD684FD04F.jpeg
 




Shadow6661

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June 17, 2018
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City, State
Ash Fork, AZ
Year, Model & Trim Level
1997 ranger 4X4
Hi,
Yesterday I noticed that my cluster temp gauge was bouncing from normal to C back to 3/4 way to H and then back to normal. It never reached hot.
Now I have no heat. Does the temp sending unit regulate the flow of heat?
I bled the system just now and there were a few small bubbles and then a huge burp but that was all. Still no heat.
If the sending unit does not regulate heat then is it the thermostat, water pump, temp sensor or even heater core?
I have read that if it is the water pump or thermostat, the vehicle should overheat and it isn't.
Also, there are no leaks.
Any and all help is greatly appreciated.
 




Shadow6661

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City, State
Ash Fork, AZ
Year, Model & Trim Level
1997 ranger 4X4
Fords are a pain in the A** when it comes to refilling the cooling system. I've been working on my Rangers cooling system for several months now and still haven't gotten the heat to work properly. When it's cold out, the highest temperature the engine gets is a little over 100°. If I run the truck under load, it runs in the normal temperature range. I have bled the cooling system according to Ford, to no avail. All I can suggest is to top off the radiator, cap it and let it run for 30 minutes. Once it cools down, do it again. You could also try towing something heavy, if you're vehicle is set up for towing. If it's not, pack as much weight as you can and drive it around. I've been hauling water to my property and my truck is getting better. My response is based on the problem I'm having with my truck, and I just wanted to give you my thoughts on a probable solution. I hope this helps !
 




Mbrooks420

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Fords are a pain in the A** when it comes to refilling the cooling system. I've been working on my Rangers cooling system for several months now and still haven't gotten the heat to work properly. When it's cold out, the highest temperature the engine gets is a little over 100°. If I run the truck under load, it runs in the normal temperature range. I have bled the cooling system according to Ford, to no avail. All I can suggest is to top off the radiator, cap it and let it run for 30 minutes. Once it cools down, do it again. You could also try towing something heavy, if you're vehicle is set up for towing. If it's not, pack as much weight as you can and drive it around. I've been hauling water to my property and my truck is getting better. My response is based on the problem I'm having with my truck, and I just wanted to give you my thoughts on a probable solution. I hope this helps !
Sounds like you are overcooling. I’d surely work on fixing the problem, rather than loading it to bring the temp up. I’d start with a new t stat. How are you reading your coolant temp?
 




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