rising temp gauge

[scootercraig]

I have a Renault Laguna RT hatch S reg the temp gauge creeps up into the red but the overheating light never comes on and the car dosnt appear to over heat i`m not losing water or oil and the heater is working fine, any clues as to what is causing this please.

[logic]

Change the temp sender unit,

[mjwman]

I think you would have a clue if it was actually overheating, hissing,overflow when turning off etc.
So just change the sensor which should be located by the thermostat and can easily be unscrewed with one spanner.

If you are quick, you can whip it out and replace it before loosing too much fluid but release any presssure by undoing the filler cap first.

[TWR]

With respect to mjwman's answer, make sure you do this with a cold engine.