water gauge temp sender

[Maxtor]

I was driving our 1997 Explorer and noticed a red "check" gauge light. The water temp gauge was beyond hot. I pulled over and everything seemed ok with the engine. I let it set overnight and the next day saw that the gauge was still pegged beyond the H. I started the vehicle up and the gauge needle moved a small amount to the left, but still beyond hot. I shut it off.
Does this sound like a temp sender, or gauge problem?
I have the 4.0 sohc engine, so I understand the sender is in the front, on the intake manifold, and not easy to get to.

 

[JimMadsen]

It may be a engine coolant problem, get that figured out first beyond looking ok and then look at the gauge

 

[bobflood]

If the gauge is still pegged at hot after sitting overnight, that is a pretty good indicator that there is a sensor problem, since the coolant will obviously be cold at that time. First thing to do is unplug the wire from the sensor - the needle should then drop to zero. Then ground the wire somewhere and see if the needle jumps back up to H again - if it does, then the gauge and wiring are OK. You can try cleaning the sensor contact and reattaching it - just to see if corrosion on the contacts is the problem. Most likely, however, you need a new sensor. The gauge sensor has one wire; the ECT sensor that provides coolant temp information to the engine management system has two. Good luck.

 

[Maxtor]

Thanks;

Very good information. I can not see any sensor that has just one wire. I will be able to get the car into the garage over the weekend, to tearing it apart to find the water temp gauge sender.

 

[bobflood]

Thanks;

Very good information. I can not see any sensor that has just one wire. I will be able to get the car into the garage over the weekend, to tearing it apart to find the water temp gauge sender.

According to the schematics:
Coolant Temp sensor for engine control - Lt Green/Red and Gray/Red wires
Gauge sensor - Red/White wire

I believe that they are mounted next to each other in the thermostat housing. I have not looked at an actual engine - just going off the diagrams. Good luck.