My daughter is travelling long distance on highways.Her car is at a temperature of 213F at times, is that normal? She has a pontiac 2008.GT

the most expensive part of 3 possible replaced 2 times.
wow.
the sensor or the wires (end to end) are bad. (just one gauge fails?)
the service manual covers how this work.

I guess you meant the IP cluster engine temperature meter reads wrong and the engine thermostat is not bad, 23 years old and thermostats have design life of 7 years../
a scan tool set to scan PID, ECT sensor tells what coolant is doing.
189f to 213F is spec, temp range

the gauge coolant temp has:

Water Temperature Indicator Sender Unit
When the engine temperature is low, the resistance of the water temperature indicator sender unit (10884) is high, thus restricting the flow of current through the gauge and moving the pointer only a short distance. As the temperature of the coolant increases, the resistance decreases, allowing more current to flow through the gauge and resulting in a corresponding movement of the pointer.

these year trucks the gauge sender is not the ECU ECT sensor
and may be single wire sender.. try mostly fail this old, not the gauge
the wire on the sender can rust or even fall off.

Coil packs under the engine cover. Could also be the plastic coil tower also under engine cover. Do you lose p/w and wipers at the same time? If so, replace ign. switch.

traveling on gravel roads vechicle make all kinds noise due to vibrations.if you only hear noise on gravel road not much wrong if you hear noises all the time you have problem.

there are 2 hoses that connects the radiator to your engine. sensor is attached in one of these hoses

this 3.4 engine,could have a few problem,thermostat,leaking coolant to oil,clog heater core.

Should run around 210F.

Is the fan blowing for the vents? If not the problem is a fan issue which is much more likely. The hot water usually goes through the heater core all the time and the only reason you get heat when called for is that air is directed across the fins and coils where your engine coolant is going through. Of course the heat does not come on until the engine has heat built up in it say after about 7 minutes of run time depending on ambient temperature.

If you are not climbing steep hills or towing, leave it on all the time. Turn it off for low speed/high strain driving like towing, climbing and off-roading.

i hope this helps
-matthew

11.1 x 6.25 = 69.375 Litres

Its overheating when you go up long hills because the engine is not getting adaquete air in the system. The radiator is angled to get optimal air a certain way. It may overheat but you shouldn't start seeing smoke.