55 temp pegs hot when motor turned off

[Max888]

After two years of working on my bird I took it for a short 2 mile drive ( smiled so much my ears hurt)

My question is as I was driving the temp Guage stayed at middle but when I turned it off it pegged hot. When I started it the Guage went back to middle. Is that normal??

I think it concerns me because when I pull radiator cap off I don't see the fast flow of coolant like I do in my other older cars.
Im thinking if it cools when I start it the water must be cycling. Correct?

After two years I think I finally have a love affair, it so nice to feel benefits of money and labor

[apines]

Yes, that's normal. The gauge works backwards from what we're all used to so it looks weird at first. If you really want to be sure get an IR temperature gauge and point it at the block near the thermostat after it's warmed up.

Enjoy the ride! My '55 has been immobile for far too long; I need to set aside some time to get it rolling, too.

[Max888]

When I first come in the temp gauge reads cold ( correct side )

What you think about the coolant not running like a creek ?

Still GTG?

I did not change thermostat I may check it and put in a 160 degree.

Yes, you need to get that bird of yours up and running. You know what they say.. life's short eat dessert first. ;)

[apines]

Maybe I didn't understand the question. When it's off, it should be pinned right (hot). When you first turn it on when it's cold it should move way left toward C. Once it's warmed up it should be somewhere in the middle. If you turn it off then shortly back on while it's still warm I'd expect it to be still somewhere in the middle.

I can't speak to what it looks like with the radiator cap off; I've never run it that way. But if the temp is staying somewhere in the middle then the water pump must be doing its thing. As I recall mine was around 190F fully warmed up when measured with an IR thermometer.

[Max888]

Sorry I'll try to explain better

First start up of day (complely cold) gauge in C position

driving stays in middle

Turn motor off the turn key to "on" Guage pegs to H

Restart guage goes back to where it was when driving, in the middle

[DynoDan’55]

Needle centers instantly upon restart? It’s fairly normal for the gauge to peg ‘H’ after shutdown, since the coolant flow ceases but the head is still hot.

[Max888]

Thanks everyone!!

[Rusty57]

I’m new to this era TBird’s so this is interests to to me.

I thought that the the temperature sender and gauge in these engines are electrical units. If that is correct, how can there be any temperature reading when the engine is turned off?

By chance is this a 6 volt car that was converted to 12 volts?

I know that mechanical temperature gauges will read higher when you shut an engine off. The coolant is no longer circulating so it gets hot sitting in t(e block and head. As everything cools down the gauge reading drops.

[Max888]

The car has been converted to 12v. I completely rewired the bird and replaced some gauges.

I bought the temp sending unit/guage

Screenshot_20210816-162119_Samsung Internet.jpg (18.94 KiB) Viewed 2840 times

[swatson999]

I don't know about that particular unit, but I do know that a lot of temperature and pressure "gauges" in later-model cars are simply idiot lights in the form of a gauge: if there's pressure above a setpoint, the "gauge" goes to the middle, otherwise, it drops to 0; similarly for some of those temperature gauges, which simply indicate that the temp is not above some setpoint by indicating somewhere in the normal range.

Make sure you don't have something like that...

[swatson999]

This is not clear:

Sorry I'll try to explain better

First start up of day (complely cold) gauge in C position

Do you mean when you get in the car, with the key OFF, the indicator is showing C (the low end of the scale)? Or it shows that with the key ON (which would be expected) or after first starting the engine?

[Max888]

Guage and sensor are matched

When the car has set and motor not started when I turn key on it stays at cold

I fire it up and after driving a bit the temp Guage climbs slowly from C to middle. It stayed at that position as I was driving.

Came back to park it shut motor off with ignition off the gauge went back to C

A few minutes later I turned ignition to on ( without starting it ) the Guage went slowly to the H.

I started it with motor running the Guage slowly moved back to the middle.

Turned the motor off ignition off gauge went back to C.

[paul2748]

It's normal for the coolant to get hotter when the engine is turned off. There is residual heat in the engine when it is turned off. In turn, this heat will make the water hotter (since it is not flowing through the radiator) which will show up in the temp. gauge. As the engine starts to cool down, so will the water

[ICON 1956]

Simple science. paul 2748 is absolutely correct.

[Rusty57]

The most recent explanation from Max888 makes perfect sense. I agree that the coolant sitting in the hot block and head gets very hot when you shut the car off.

I have an a another older classic car with a mechanical temperature gauge. The temperature goes up quite a bit when I stop the engine, especially if I have been driving it fairly hard. It will take a few hours for the gauge to drop back to the lowest reading.

Thanks for the clarification.