OEM water temp gauge... Reliable safe zone?

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French demon

French demon

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As you known the OEM water temp gauge isn't very detailed, nor graduated. No red line.
Is the central zone a really safe zone? And as long as the needle stay in this zone, my engine will run at a normal temp?

Water temp gauge.jpg
 
yes and maybe not. These thermal instruments were fairly dependable when new but... without opening for visiual inspection and then testing with decade Ohm's resistor bank, there is a bit of gamble today.
 
Get a thermal temp gun.

Start the engine and let it idle.

Note the needle position and measure the base of the temp sender.

Do this every 5 minutes or so.

Note the needle position and the temp.

Now you know about what temp the engine is for the needle position.

As for the "normal" range. The OEM decided that the engine is safe to operate in that range.


Note: 67 dart up through mid 68???? (Maybe 69) had a temp gauge with the "normal" range shifted to the right.

Screenshot_20230628-120608.png


They later changed the face plate to shift it back to the left.

Screenshot_20230628-120425.png


The mechanical part of the gauge is the same just the range is changed.

So at the same engine temp the needle on the later faceplate is about mid range

And on the older plate the needle is just past the low end of the scale.

Note that the upper end of the scale the engine would be hotter on the older face plate but still be in the "normal" range.

Screenshot_20230628-120608~2.png


Screenshot_20230628-120425~2.png
 
Thank you, sirs, for your advices.
My needle stay in the safe zone, but I will measure the temp sender base with a IR thermal gun (I have one).
This way, I'll know if the gauge is accurate...
 
A note about thermal temp guns.

They are not accurite on shiny surfaces, and the base of the temp sender will probably be a few degrees cooler than the coolant the tip of the sender is measuring.

IMHO don't get too hung up on the exact temp and just go with this is normal and this is not.
 
I made some road tests today, with a 86°F outside temp

The engine temp while driving :
temp3.jpg

20 minutes later, back home, with the temp gun aiming the sensor base :
red dot.jpg

temp1.jpg

Everything seems to be normal, and the gauge correctly calibrated :)

:thankyou:
 
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For the record I rented a new jeep grand Cherokee and found a screen with temps

This was crushing on basically flat ground at 80 ish mph


I noted the oil temp was consistently 10 deg hotter than the water and the trans was in the 170 range.

Going up inclines everything increased.


Interestingly the oil pressure was consistent (about 30 something) except when it kicked down to 5th or 6th gear (8 speed auto) then it went to 75psi


Which I could find a tach screen.
PXL_20230629_230404562.jpg
 
Post a photo of the guage AND the temp gun at the same time after it's warmed up and still running.
 
Close to the "C" as I can get it.
 
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