Thread: Coolant

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I would suggest installing a sacrificial anode if you have not done so already. A little extra insurance never hurts.

Originally Posted by firebird77clone

Seems to me, before you could verify sending unit (by measuring resistance) you would first need to verify temperature. So the afore mentioned heat gun is a good start.

Once you know the actual operating temperature, you could then test resistance of the sending unit to know which is bad, the sender or the guage.

I put one in boiling water with ohm meter leads clamped to it. We know that temperature.

Teflon tape or sealer on the threads------------

If everything checks out you might check because steam also doesn't conduct heat very well, if you have the sending unit in a npt reducing bushing you could have it in a air loc or air bubble measuring steam or air temp and not water temp, thats what was going on with mine, I loosened the sending unit until water came out and my problem was cured.

I'm with Jerry on this, usually air/steam pockets make it read on the high side. The thread sealant increases the resistance, the sending unit is a heat sensitive resistor the more resistance the cooler the gauge reads. Of course there's always the possibility that the gauge is out of calibration or it has a mismatched sending unit.
And as mentioned previously, real easy to check the actual temperature with a laser, most shops will read it with their laser for free (or very low fee).