^^^ +1
You should be using a 192-195deg thermostat.
The t-stat sets the minimum operating temp of the engine, which should be around 200-220deg
The t-stat has a rubber gasket that must be installed or coolant will flow past the t-stat and engine will run colder than it should.
T-stats often have a "jiggle" valve, a hole in the plate with a metal pin in it, this is there to vent any air that might get in the system, so this "hole" should be mounted at the 12:00 position so the air will purge out.
The Lima 4cyl engines don't generate alot of heat at idle, but should warm up to 190deg within 8 minutes of driving maybe 10min. idling.
These engine also have an intake pre-heater that has coolant flowing thru it, that acts as a radiator in colder weather.
Some put a piece of cardboard in front of the rad in the winter to kept temp higher.
A cold engine has no cooling system pressure and idling for 10 minutes while warming up without rad cap should be fine, it should not overflow.
The water pump circulates coolant so the "pump" description is a bit misleading, it generates no pressure, it just pushes coolant around engine.
If there is air in the heater hoses the water pump can not push it out of the way easily, so you have an "air lock".
It is often a good idea to get 2 hose clamps and a hose connector(metal) and cut a heater hose at it's highest point.
Then when refilling leave this hose open and raised so all air is vented(make sure heat control is on HOT, so if there is a valve it will be open), after coolant is coming out BOTH heater hose ends connect the hose and tighten clamp.
If one end of the hose doesn't have coolant coming out then use a funnel to fill it, jiggling it to purge the air.
Any air left won't be enough to cause an air lock.
Put rad cap on and start engine
Any air left in the system will be purged via the rad cap into the overflow tank when coolant gets above 220, make sure overflow tank has coolant and is filled to the COLD mark before starting engine.
If overflow tank ever gets empty air WILL be sucked into the engine, also give the overflow hose a good look, a crack in that hose will let air into the system.