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Coolant temperature sensor connected to throttle

Exploring XLT

Never Stop Explorering
Elite Explorer
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Location
Holden, Alberta, Canada
City, State
Holden, Alberta
Year, Model & Trim Level
93 Ford Explorer XLT 4WD
Odd thing happened on my way home from work, any time I added significant load, downshifted, or otherwise stressed the engine, the temperature sensor would drop all the way down to cold, immediately jumping up again if I released the throttle. Any ideas?
 



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Odd thing happened on my way home from work, any time I added significant load, downshifted, or otherwise stressed the engine, the temperature sensor would drop all the way down to cold, immediately jumping up again if I released the throttle. Any ideas?
@Exploring XLT .
Engine torque increase tries to "raise" engine up off the driver-side engine mount, then settles down when torque decreases. This effect is small with mounts in good condition. If a mount is softened, or broken, the effect can be drastic. So much so, GM began specifying short chains welded onto mounts one year as a "fix" for faulty mount design.

If this is happening with your vehicle, trace along wiring, especially that harness carrying the temp. sensor wiring, for possible shorting-out electrically by crushing force somewhere.

When I ran a service station years ago, a guy dropped off his Chevy, needed "new mounts". He left, I started it outside, ready to pull into a bay, gave it considerable gas, and it lurched forward suddenly, off the gas pedal, it kept going under power, heading for the plate glass windows out front. Fortunately, i stopped it. Opened hood, stood on brakes, gave it gas in drive, entire left side of engine lifted up about 5 inches, LOCKED the throttle open! Then I noticed the dents in his hood....... true story! imp
 






@Exploring XLT .
Engine torque increase tries to "raise" engine up off the driver-side engine mount, then settles down when torque decreases. This effect is small with mounts in good condition. If a mount is softened, or broken, the effect can be drastic. So much so, GM began specifying short chains welded onto mounts one year as a "fix" for faulty mount design.

If this is happening with your vehicle, trace along wiring, especially that harness carrying the temp. sensor wiring, for possible shorting-out electrically by crushing force somewhere.

When I ran a service station years ago, a guy dropped off his Chevy, needed "new mounts". He left, I started it outside, ready to pull into a bay, gave it considerable gas, and it lurched forward suddenly, off the gas pedal, it kept going under power, heading for the plate glass windows out front. Fortunately, i stopped it. Opened hood, stood on brakes, gave it gas in drive, entire left side of engine lifted up about 5 inches, LOCKED the throttle open! Then I noticed the dents in his hood....... true story! imp
Should I look at/replace my motor mounts as well then?
 






Should I look at/replace my motor mounts as well then?
@Exploring XLT
Well, I threw out an idea which is conceivable as the cause, but actually rather far-fetched as the designers seem to have reinforced eng. mounts (at least those I've seen lately), to prevent such occurence.

Why not try the little experiment? Lock the brakes, step on gas pedal in gear, look if eng. perceivably lifts upwards on it's left side. imp
 












Sensor connection seems ok, thought I would mention, sitting idling the upper radius hose is super hot, while the lower is relatively cold, I dont think it could be cooling the coolant that effectively sitting there, is it possible that the rad is plugged? Only allowing flow when I increase the rpm, hence the sudden temp drops?
 






If your radiator was plugged, you would most likely overheat.

For the gauge to swing from normal to cold (off) then back to normal is most likely a sensor or wiring fail. I just don’t see the coolant temp swinging that much in a properly operating engine.

Are you certain the coolant is full?
 






The reservoir is full, cant check the rad as it is running
 






The reservoir is full, cant check the rad as it is running
You should never open a hot radiator, that is not what I suggested. Next time the engine is cool, open the radiator cap and check. A bad radiator cap or other pressure leak could prevent coolant from being drawn from the reservoir.
 






Nah I just assumed you didnt know it was running, will do
 












Basically, I'm using it on a 12 hour night shift for a few days
 












Didn't someone once have some wierdness with temp readings and discovered the sensor was covered with junk on the inside, the coolant side?

I don't know if you are good with voltmeters, but for what it's worth, the sensor is 74 ohms cold and 9.7 ohms hot. I'm just providing that for reference.
 












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