The sensor with the one wire on it (white arrow) should be the one for the indicator. To verify just pull the wire off and see if the indicator still works.

 

Thanks, jetwhine, I concur.

In doing research I think the gray one (green arrow) is the Ignition Coolant Temperature Sensor. What is the yellow one (red arrow)?

All three of these are threaded into the coolant.

 

can you tell me what color the wire/wires are?

 

Finally got this pig back together. Had to change all of the hoses and that meant cutting a couple of hose clamps.

The one wire that went to the sensor was yellow with a thin dark green stripe once you look under the covering insulator.

I now suspect the gauge (or wiring) has an issue. We got it all back together and took it for a test drive - the needle went entirely to the red area within a few blocks but there were no overt signs of overheating - no rattling of the valves, the engine ran smoothly and power remained the same. When we opened the hood no steam, no hissing etc. It just didn't "feel" hot in the way past experience with overheated engines did.

So now we are going to try an aftermarket gauge, but does anyone know if we have to change the sensor?

 

I still would try the sensor first. Taking the gauge cluster out to find you have a bad sensor would not be my first choice. Unless you can prove that the temp sensor is good, then I would go for the gauge.

 

To clarify, we did install a new sensor with the same results. So what we are doing now is installing an aftermarket gauge which does come with it's own sensor, so we will have tried two new ones by the time the process is done. I will try and remember to post the results.

For anyone thinking of installing an aftermarket gauge kit make sure you go to a parts house to look at the new gauge kits as you will need to check out the sensor's physical size and threads to make sure they fit your auto. I couldn't find a compatibility chart online.

 

Any resolution to report, castironcook? I'm having these same issues on a truck I'm looking at buying....head gaskets replaced, but still overheating.

Thanks.

 

At the end of the day the ended up changing the fan clutch, and that had little effect though it was obviously worn. We had other issues crop up, so took it to friends who are mechanics. Left it with them for 3 weeks. Yeah. Three! They worked on it as a hobby, sort of.

The one thing NONE of us believed was an issue was the water pump. But that's what it was. By the way, during this whole thing we changed out the starter for a new one. The first one we installed (brand new) was bad. And the same thing happened with the water pump. The first replacement one was bad.

We still don't have all of the sensors replaced. We can't find one of them.

 

So the bottom line is: that it was really overheating, and that gauge was working properly?