Rando Temp Gauge Question

[galaxy]

So I recently learned through conversations on here what the fan turn on temps are for low and high. Forgot the numbers, but they're up there. Which got me thinking of a random question. With coolant temps soo high, when, if ever, would the temp gauge needle start to move to indicate there's a problem? Is there a published temperature for when the needle would depart the "normal" position and indicate an overheat? It must be pretty darn high.

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[cerbomark]

good question. and I wonder if there would be an idiot light too?

 

[engineermike]

Here ya go.

 

[galaxy]

Soooo, that’s oil. Wrong topic. Great info tho.

 

[cerbomark]

Soooo, that’s oil. Wrong topic. Great info tho.

those numbers are a little hot for coolant , lol

 

[engineermike]

My bad.

There is no coolant temp sensor. In some cars you can scroll through the menu and find the CHT and compare to the gauge if you like. You can log the pcm’s calculated coolant temp if you want to establish a correlation. Oil temp isn’t so easy.

 

[galaxy]

There’s gotta be a coolant temp sensor somewhere, no?? Because it uses coolant temp to turn the fans on…or so I was led to understand.

 

[Skye]

I've attached a document which provides several indirect references.

If you open the document and search for "coolant", several processes either stop, fault or reach their limit between 230-250 F / 110-120 C.

The graphic relates to fan speed, at what temp fans #1 and then two engage.

Edit,

I believe Cylinder Head Temperature (CHT) is implied from other inputs. There is no actual coolant sensor.

 

[Skye]

Doing some self-study this morning, the Cylinder Head Temperature sensor is a thermistor; the resistance of the sensor changing with temperature. As the temperature increases, resistance decreases, allowing for a greater flow of electricity through that circuit, registering as a higher reading on the gauge.

When CHT becomes too high, the car enters Stage 1: the driver receives warning lights to pull over and shutdown.

If the driver does not notice the light, or continues anyway with an ever-increasing temperature, the car can later enter Stage 2: four of the eight cylinders will be deactivated, those cavities pumping nothing but air, in an effort to bring temperatures down. RPMs are limited to no more than 3,000.

If the driver continues still, engine shutdown will occur, at Stage 3.

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