Can an empty coolant reservoir tank cause the temp gauge to rise to ''H'' without the 2003 civic actually overheating?

Sounds like a possible heater matrix leaking in side the car and loosing water hence the temp goes up and a film on inside screen

why not check the coolant tank.. coz if it is empty the sensor cant real the real reading.. it is likely that if it is just the vapor. any sensor cant read the proper temp.

If your coolant overflow is bubbling then regardless of what your gauge says you are having overheating issues. If your coolant is missing with no aparent leaks then you need to check your oil for a milky consistency and apearance which would most likely point to a blown head gasket. This would also explain overheating. Hope this helps

a load of codswallop
for a temp gauge to work , it has to have coolant around it
when there is no coolant the gauge will not get to overheat
most likely it would start because the motor has been cooked
what the people were try to say is that if the coolant temp sensor is working and it gets too hot the engine light comes on and it goes into limp mode which still allows you to get off the road to check things out

This actually will work on both.. It provides a temp into your ECU and will also go to the fan. I would recommend repairing the wires.. Best of Luck

check the thermostat good luck

the gauge is going above half, but is it actually over heating? could be a faulty coolant temp sensor sending an incorrect temperature. when you changed the radiator, was the rad cap also changed? if the cap is not holding correct pressure, it will lower the boiling temp of the coolant and cause it to overheat. an infra red thermometer is very useful for diagnosing this, point it at the thermostat housing and see what the temp is there, that will tell you whether the temp gauge is accurate or not. good luck!

You say it's overheating, more info needed such as:
Is the engine temp gauge showing that it's overheating?
Is it actually 'boiling over' and losing coolant?
If it's running hot, but not losing coolant, check to see it the cooling fan is operating when the engine temp rises. You may have a bad cooling fan switch that is not signaling the fan to go on to lower the engine temp.
It could be a stuck (closed) thermostat that is preventing proper circulation of coolant after the car reaches operating temp.

did u bleed the motor and lett the air out of it if not it wont fill up even thow you think it is full it is not if you did not bleed the air out