The thermostat could be stuck, or the water pump may be bad. Removing the thermostat you can reconnect the system to see if water flows, if not then check your water pump.
from the top to the bottom
no
Low coolant?Cooling fan not working?Defective thermostat?Radiator clogged or air flow resitricted?Defective radiator cap?Defective water pump?Airbound? Low coolant?Cooling fan not working?Defective thermostat?Radiator clogged or air flow resitricted?Defective radiator cap?Defective water pump?Airbound?
No. The thermostat controls the flow of water through the radiator, not the heating core. Using a thermostat with a higher temperature rating delay the opening of the thermostat (and the flow of water to the radiator) until that higher temperature is reached. This will cause the coolant to run hotter.
Low coolant? Thermostat not opening? System airbound? Radiator plugged or flow restricted? Defective radiator cap? Water pump not operating? Clutch or cooling fan not working?
The boiler has a circulation pump that circulate the water
Low coolant? Thermostat not opening? Radiator plugged? Radiator air flow restricted? Hoses collapsing? System airbound? Water pump not working (defective impellor)? Bad radiator cap?
The water does not flow through the radiator until the engine is at operating temperature. At that time the thermostat will open and allow it to flow.Sometimes you are unable to see it, depending on the direction of flow. Increase the engine rpm and you should notice a change.
possible hole in hose
Once the thermostat has opened, the hot coolant flows from the thermostat housing on the engine into the top of radiator and out the bottom of the radiator back into the water pump.
When the thermostat is open the coolant will flow through the top radiator hose in to the radiator and out to the water pump through the bottom radiator hose
Normally gravity, but osmotic pressure can also cause water to flow.