My 06 has started to have a very erratic engine temp and I'm unsure why?

The truck has never ran hot at all, until I was coming home from a short trip hauling a load of water (15,000#) just happened to look down and the temp gauge was up almost to the middle of the "Normal" zone and approaching the red line!

Never having seen this before I shifted to Neutral and coasted for a 1/2 mile or so and the guage obviously creeped back down in that time frame of 20 seconds or so?

So relectantly I stuck it back in gear and slowly and lightly drove the last 2 or 3 miles home.

Coolant level is normal and coolant is clean.

One strange thing though, I never heard the fan kick in at all?

So I'm wondering where my problem is? Bad sending unit? Bad guage?

Water pump smoked? Thermostat gone bad?

I'm inclined to think an electronic issue since the fan didn't engage?

Advice would be appreciated.

 

If there are no overt signs of heating with CEL's I would guess the cluster or cluster controller is the source.

 

Anyway to test this?

Also, what would I reliable way of testing the actual engine temp vs what is showing on the guage be?

 

You can run a cluster test and see is it finds any problems. If its a controller problem or data bus problem probably won't see a code.

Adding a analog gauage with a sending unit in the coolant is really the only way to see if the gauage is correct. Then, you need to have the probe close to where the OE sensor is because the variation of temperature thru the block could cause a disparity in the readings.

 

Where is the stock engine temp sender unit on these things?

 

Left side of the engine right in front on top. Small sensor with 2 wires plugging to it. Its right above the T-Stat housing