2011 Ford Ranger 4.0 V-6 ...

generator12

Senior Chief Petty Officer
Joined
Jul 9, 2010
Messages
666
Getting a "Check Engine Light", and the code is low engine temperature. The temperature gauge in the cab is at about 1/3 scale. Plenty of heat coming into the cab, even in zero weather. Gas mileage doesn't appear to have changed, and she runs smoothly and without disruption. The only sign of a problem is the CEL.

I'm trying to discern whether it's more likely the thermostat or the temperature sensing system before I begin to open it up because I only want to do it once.

I tried an infra-red pyrometer on the thermostat housing and the highest I can come up with is 140 degrees F. I'm not sure the external surface temp. tells me much in any case, but I want to judge it against the normal operating temperature for the 4.0. The problem is that I can't, for the life of me, find that temperature spec anywhere.

Does anyone have knowledge of this engine and its normal operating temperature?

Thanks guys.
 

GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
Messages
49,038
If no one knows the normal temp, check and see what the thermostat temp is on an auto part site. The OEM replacement one for mine says it opens at 195.

Your temp should be close the the thermostat opening temp. I think you are running too cool.
 

wrench 3

Commander
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Aug 12, 2012
Messages
2,108
It should be running 190*. They will usually set the code if they don't see around 180.
The thermostat is a maintenance item anyway, change it.
 

MTboatguy

Fleet Admiral
Joined
Jul 8, 2010
Messages
8,988
It is pretty common for the temp sensor to go bad in these motors, that is the same motor that Ford has been using since 2000, my 2003 Explorer with that motor seemed to go through temp sensors about every 30K miles, I know it seemed like I was always replacing them.
 

dolluper

Captain
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Jul 19, 2004
Messages
3,900
A three wire coolant temp sensor will show in the cab gauge as right but computer wrong temp if bad.....only a scan tool with an engine live display will show the difference in the two
 

keith2k455

Chief Petty Officer
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Jul 23, 2012
Messages
558
I would say 140 is too low. Nothing will pass emissions at that low of temp. I would expect that truck to run right around 210, 195 at the lowest. If you block the fan with cardboard and take it for a drive, does it run hotter?
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,657
I would say 140 is too low. Nothing will pass emissions at that low of temp. I would expect that truck to run right around 210, 195 at the lowest. If you block the fan with cardboard and take it for a drive, does it run hotter?

Pass emissions ?

Whats that?
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Test the thermostat on the stove with thermometer and see what temp it opens at. If it opens correctly, it's your sensor.
 
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