It's one thing after another right now with the old girl.
Out for a drive and noticed the temp gauge hanging at around the 1/4 mark (sits just below the halfway mark when warmed up normally).

Interesting thing is the idle speed is right where you would expect it to be with the temp at 1/4 (at or about 1000rpm)

Occasionally the gauge reading would go up a bit (and the idle speed would drop - as it should - as the car warms up). only at this point the engine should be at operating temp as I've been driving for 15 minutes.

So what the heck is happening here? Is it a temp sensor issue? Is it true that there is one that sends the signal to the ECU and a separate one for the gauge?

Tomorrow I will hook up the scanner and see what temp the computer thinks the engine is at & also see what the temp gun says at the upper hose.

Clearly the computer is in this loop since that's the only way the idle speed would change with the engine temp.

Sound familiar to anyone?

 

Have you made sure the coolant is full? Usually the only time the coolant isn’t reaching its normal temperature is when it’s gotten low and isn’t circulating so the sensor isn’t giving you an accurate reading. I would check your radiator to make sure it was full before starting the car again

 

I will certainly take a look at that.
Timing belt was done a month ago, obviously coolant was drained to get that done.
Checked multiple times over the next few weeks - level stayed topped right off. Did not move even a little bit.
Temp (on gauge) stayed dead-on what it has always shown.
I guess it's possible some air has worked it's way to the top? (after all this time).

Like I say - summer of love for this car. One thing after another

 

If you've turned on your heater, that's probably where some of that coolant went...

 

It was down a little ... maybe a half inch down from the full cold line (when cold obviously).
Wouldn't think that's enough to have an effect - but who knows. It's topped off now.
We'll see what happens.

 

I am not sure what vehicle you have? But mine has a bleeder screw at the high point of the cooling system to ensure no air gets trapped above the radiator cap, you should look and see if your vehicle has this design? If you’re certain the coolant level is correct then you should look at replacing the coolant temp sensor. They aren’t very expensive, make sure find a genuine OEM part, you’ll want the one that installs on the intake manifold, and not the one that’s on the radiator, that one just controls the fans. It could be that the sensor has just built up resistance in it or there could be debris built up in coolant passages. So you might need to flush the coolant system, also inspect the wires to the sensor, for damage or signs the insulation may be falling off or something.

 

'94 SC
If you're talking about the fill plug on the water neck - yes sir.
Got one ready to go in. I was going to do it with the timing belt but after four days fighting with it ... i just couldn't wait to get it back together and missed it altogether.
Thing is, it was never issue until now. At least I think so. It's the girlfriend's car and for all I know it's been acting up for 5 years I just happened to catch it.
I did (almost) a complete coolant change when i did the timing belt. I got something like 9 1/2 out of 11 litres (total capacirty) out of it. I was pretty surprised actually. Pumped as much as I could out of the block with with a round-up pump. Worked pretty darn good
Lots of good ideas there ... I'll let you know how it all goes!
At least it's not boiling over Thanks for the input!