Problem with temperature gauge

[JeremyNH]

Something to consider is that the temperature gage and the ECM use different sensors. The ECT to ECM is the two wire sensor near the Tstat and the sensor to temp gage is one wire sensor in the drivers side head. Put a scanner on as you drive around and see if the ECM is reading fluctuating temperatures same as the gage. Given that you haven't said you're getting any noticeable change in engine performance it's doubtful that temperature is in fact fluctuating meaning that you don't have a problem with your cooling system but rather the gage or sensor. The one wire sensor reads high on a short and low on an open so you could have an issue with the temp sender, harness (it is held by a metal bracket), or wire to gage. I installed a new sending unit in the head when I built my stroker. The new sender was reading about 30-60deg high which almost caused a heart attack on first fire. I swapped back to the 30 year old sensor to get a good reading on my gage after break in. I was monitoring the ECT in HP Tuners the entire time and the ECT temperature was stable 185-196 after warm-up while the temp gage was showing 215-260.

 

[Russ B]

Go back to basics before you go full bore , like me, I usually overthink a problem. Start with the worst case and then back to simple. Do you have a scanner? Absolutely mandatory nowadays. Go to engine data and watch the engine temp. More reliable than the dash gage. I would first pull the thermostat and run it a bit and see if it holds temp. I should be low. Not sure if you said about changing water pump.

 

[Georgiabigfoot]

What ever became of your temp
Gauge issue ?