Question about thermostat

[kevinbmx77]

Does it always let alittle coolant through it? Or is it meant to stop flow completely till it reaches its tempature?

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[RonD]

A good thermostat will have a "jiggle valve", yes that is it's actual name, lol.
It is a small hole in the thermostat plate with a metal pin in it.
It's purpose is to let air out when refilling the system.
Metal pin "jiggles" when coolant is flowing and keeps the hole open.

So yes the jiggle valve will let some coolant flow.

But no, the thermostats main valve will be closed tight, until +/- 3deg of its rating.
A 195degF thermostat will be completely closed until coolant at the thermostat location is at 195degF, and it will be fully open at 210degF, approx. 15degF above rating.

Ford uses 190-195degF thermostats because operating temp from 190-210degf helps keep oil cleaner(longer engine life) and gives better MPG, more efficient combustion.

Thermostats use WAX in the center cylinder as the temp sensor, just FYI

 

[kevinbmx77]

A good thermostat will have a "jiggle valve", yes that is it's actual name, lol.
It is a small hole in the thermostat plate with a metal pin in it.
It's purpose is to let air out when refilling the system.
Metal pin "jiggles" when coolant is flowing and keeps the hole open.

So yes the jiggle valve will let some coolant flow.

But no, the thermostats main valve will be closed tight, until +/- 3deg of its rating.
A 195degF thermostat will be completely closed until coolant at the thermostat location is at 195degF, and it will be fully open at 210degF, approx. 15degF above rating.

Ford uses 190-195degF thermostats because operating temp from 190-210degf helps keep oil cleaner(longer engine life) and gives better MPG, more efficient combustion.

Thermostats use WAX in the center cylinder as the temp sensor, just FYI

Thank you, i put a new thermostat in today because there was a 160° in it before and it needed the 195° like you said, i had the top hose off when i filled the radiator to check for leaks and water came through the thermostat. The truck definitely runs cooler now.
Im curious about that wax though, does it melt and allow it to open? Or am i thinking of that wrong?

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[RonD]

Yes exactly, but it pushes it open.

The wax is sealed inside a copper tube with a piston, when heated the wax melts, and like most things it expands in volume when heated, this pushes the piston that opens the thermostat valve.
When it cools it shrinks in volume and valve closes with spring pressure.

 

[Andy D]

Are the bi-metallic spring T-stats extinct?

 

[RonD]

Not sure they were ever used in engine/coolant systems?
They are used in Fan Clutches.
And in home heating and cooling thermostat systems.

I suppose there could have been some, but I would think corrosion would make life span an issue.
Bi-metal, by its very nature, is electrolysis prone.