Thermostat install-I think I fouled up

[odeek9]

Hey,
I put in a 160 thermostat a couple of months ago-I have a "thing" about heat and the damage done at times. The truck never ran over 175 but I'm an idiot.
It ran too cold ie hesitation, stalling, and the heater was worthless-it's gotten relatively cold here. And I recently read that if the engine runs too cold then condensation may develop and damages the cylinders, etc.. Made sense to me. So today I put my 180 degree thermostat back in-it wasn't very old. Now the truck runs really cold! After 1/2 hour of idling and a short test drive it seemed to run fine but it never got over 140 and hung around 130 when idling! I checked the block, etc. with my laser temp. gun and they were cold too. BTW, the manual temp gauge is fine. What happened? The only thing that I may have done incorrectly was I may have put in the old thermo w/o the seal . I vaguely recall playing with a couple of them at some point. Would that make it run as if there wasn't a thermo in place at all? I'm guessing yes. I'll redo it tomorrow but hate doing so as the shroud for the timing belt is a nightmare to put back on.

Any thoughts? Thanks

 

[RonD]

You should actually be running a 192-195degF thermostat.
Just FYI, S.A.E.(the oil guys) and Ford did a long term study about engine temp

Above 190degF was found to clean the oil the best, i.e. burn off water and fuel contaminants, and keeps cylinders temps hot enough to give best MPG, so best efficiency.
This is why ford switched to 192degF t-stats
And a working t-stat has nothing to do with overheating, overheating is when engine coolant gets above 240degF, Ford Temp gauge center line is 210degF.
160, 180, 195degF t-stats would all be open all the way at 200degF, so not a t-stat issue if coolant goes above that
T-stat sets MINIMUM coolant temp.


Your thermostat is open, broken.
Start engine cold and feel upper rad hose, it will be cold, wait a minute or two and feel it again, it should be just as cold, if upper rad hose is warming up with the engine then t-stat is open.

T-stats use a wax inside the center rod that softens with heat opening valve to let coolant flow to rad, if t-stat fails it is suppose to fail open as that is the best "fail safe" for this device.

 

[odeek9]

Thanks. Well it appears that for many years I've had no idea of what the purpose of a thermostat is (along with many others I believe). I always thought the thermostat kept a portion of the coolant from circulating until the engine reached a specified temperature and then opened thus releasing more fluid to course through the engine and, in turn, cooling it down. Thanks for the lesson.

P.S.: I had checked the upper hose and it was only mildly warm following the test drive

 

[RonD]

Upper rad hose shouldn't get warm until engine coolant is above thermostat rated temp, 180degF in your case but 192degF would be better.
It generally takes 5 to 8 minutes for a t-stat to open the first time, depends on outside temp.


The thermostat does do what you said, the radiator and the coolant in it are not used unless needed.
The water pump circulates coolant thru the engine and heater core.
If coolant gets above t-stat's rated temp then it opens slightly and some of the warmer coolant flows into upper rad hose and upper rad, and is replaced by coolant flowing out of rad to water pump on lower hose.
When the colder coolant gets into engine t-stat closes again until the new coolant is warmed up, this process continues to repeat, on warm days or if you are climbing a long grade or pulling a trailer, the t-stat may open for the first time and stay open because rad is needed to bleed off the extra heat being generated by engine load or the coolant in the rad is not all that cold from warm weather.
But thermostat will cycle open and closed to maintain it's temp rating and keep engine at that minimum temp.

Thermostats also need a Jiggle Valve, it is a hole in the t-stat plate with a loose metal pin in it.
This hole needs to be placed at 12:00 position when installing t-stat.
The hole is there to let any trapped air out from behind t-stat, this makes sure t-stat is always submerged in coolant so it heats up correctly and opens when it should, air doesn't conduct heat like fluid does.