1955 Ranch Wagon with a 302 engine/ Temp gauge

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poolplayer1

Senior Member
I drove my 55 Ranch Wagon about 45 miles and the temp.was at 170 degree all the time. I came home and parked it and shut the engine off.As I did that,I noticed that the temp. gauge went all the way to 250 degree with engine off. What could cause the temp.gauge to rise when engine is shut off. When I shut it off,there was no water spill or leaks coming off the radiator at all. Just wondering if this is normal or something that I should be concerned with. The engine is completely rebuilt and only has about 120 miles sine the rebuilt. All is new in the engine other than the block,which was cleaned and tested completely. Thanks for your help and suggestions. The gauge is a mechanical type connected to the intake manifold next to the thermostat housing.
 
When you shut the engine off the coolant is no longer being circulated by the water pump and cooled by air flow thru the radiator. So it just sits there being really warm until it cools down on its own.

If it isn't 'boiling over' and spitting coolant out the overflow tube at the radiator cap it should be fine.
What is the pressure rating on the radiator cap? Something under 15 ???

I'll bet it's a very common situation but isn't noticed on most cars because the Temp gauge is electric and turns off with the key when the engine is turned off.
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dmsfrr said:
When you shut the engine off the coolant is no longer being circulated by the water pump and cooled by air flow thru the radiator. So it just sits there being really warm until it cools down on its own.

If it isn't 'boiling over' and spitting coolant out the overflow tube at the radiator cap it should be fine.
What is the pressure rating on the radiator cap? Something under 15 ???

I'll bet it's a very common situation but isn't noticed on most cars because the Temp gauge is electric and turns off with the key when the engine is turned off.
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Click to expand...

Very true what you said. I have heard this condition called "heat soak" and "latent heat of absorption". Not hard to understand that when temps in combustion chamber reaches a couple thousand degrees (I have been told that) and when coolant stops flowing the engine temp will rise. Does the inside of a combustion chamber really get that hot??
 
Thanks guys for all your good input on this matter. dmsfrr,thanks for the link about how the coolant heats up in the cooling system.Very informative.
 
Poolplayer are you reading the dash gauge or a separate gauge cluster? If you are using the stock Dash gauge, how did you hook it up?

I need to install a resistor between my Dash Gauge to my 302 temp sender. Normal operating temp read out is just a bit off the upper arch on the Hot side. Temp is normal using an infra red reader.
 
poolplayer1 said:
I drove my 55 Ranch Wagon about 45 miles and the temp.was at 170 degree all the time. I came home and parked it and shut the engine off.As I did that,I noticed that the temp. gauge went all the way to 250 degree with engine off. What could cause the temp.gauge to rise when engine is shut off.
Click to expand...


When I used the factory temp gauge on my '54 Ranch Wagon, which is electrical, the needle almost always pegged hot after running the car at normal temp a while. This is common, I gather, for the heat transfer from block to coolant after shut off, at least as measured at the sending unit.



I went to a decent mechanical gauge, in part, because I wanted an idea of how much that transfer actually is (again, at the sensor.) Also wanted a numerical gauge instead of hash marks.



I found with my engine that the transfer is generally about a 15 degree f. increase. Maybe 20 degrees on hot days.



My differential readings may be understated a bit, as my sensor needs a small adapter to install it in a y-block, which lifts it maybe another 1.5" up from the where the original sending unit was. Nevertheless, I'm a little surprised that you're finding 80 degrees difference between running and non-running.



Is that a mechanical gauge? Is it newer or older? Or did '55's have a factory electrical gauge with numbers? I wouldn't worry about it, as it sounds like your engine's running temp is good. I just have come to distrust these original factory temp gauges from this era of Ford. I thought my car was near overheating on warm days, but when I put my new gauge on I found it was the opposite: the engine coolant was running too cool because of a faulty thermostat. I now have a clearer idea of what the temps are.
 
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