Temp sending unit??

[RagTop]

I was in a drive thru at Starbucks that was verrrry long. My temp gauge stayed just about center and I was feeling very satisfied when I looked down and it had shot up to the top of the gauge! I slipped it into neutral and revved it up to about 2K rpm with no joy. When I backed off the throttle the gauge began dropping back toward the middle. That just doesn't make any sense. With the higher revs the engine was pushing more coolant and that should have caused the temp to ease off. When I put it back in gear and let it idle, that should have caused it to continue heating up since it was pushing less coolant and straining against the torque converter. Neither result occurred. When I let it idle, the temp gauge immediately began heading to the middle of the scale. I watched it promptly move down. Something I don't think is a believable result. Could it be my sending unit? I'm hesitant to change it because the last time I did, about 18 years ago, it took three senders before I found one that didn't produce irrational gauge readings. FYI, I'm running an aluminum water pump, an overdrive pulley, a three row 20" radiator, a 160* thermostat, a five bladed Ford fan with that funny offset blade, and no shroud. Ambient was probably around 97* at the time. Suggestions?

 

[Horseplay]

Much like oil pressure, you need a real gauge to tell you actual temps to really know whats happening. You question the sensor and I would counter how do you know its not the gauge? I do agree the scenario as you paint it does seem odd. Why don't you get aftermarket gauges that fit in the stock location as a happy medium? Long term I am willing to bet you would end up loving them.

 

[Midlife]

I would recommend a 180* thermostat; the 160* doesn't allow the water to sit in the radiator and cool enough before entering the engine compartment. Essentially, you have a free-flowing system that is always running. In that situation, the only cooling effect is airflow. Your weird situation may be due to the thermostat and the funky fan blade. I'd also recommend a shroud.

 

[Boom]

As mentioned a different thermostat and real gauges will go a long way to making the car run better and give a better feel for whats going on. A shroud is a good idea as well.

I seem to remember there is an easy way to test the sensor. Something about resistance.

 

[B67FSTB]

There is always a "delay" between action and reaction . Between revving the engine rpm and reaction of engines temp.
Nevertheless , you could install a second temp meter in the engine bay to check .
I did install one near the radiator and put the sender in the top radiator hose.

 

[3175375]

Get one of those thermal scanners

 

[rbohm]

it sounds to me like the IVR is starting to fail. i had a simlar issue many years ago with my 66 coupe, when when my temp gauge went high the oil pressure gauge went low. replaced the IVR and it stopped happening.