flashing temperature symbol on mk 4 golf gti turbo

[minge]

can anyone help.just recently on my gti just before i start the engine the temperature symbol starts to flash then a message saying "stop" check coolant.the manual says if this happens to check coolant level,which is fine,then to check the fuses for the fans,which are ok.if i turn off the ignition then back on again the warning message goes off for 3-4 days then reappears again.anyone know the problem?

[AlBags]

That would likely be the sender itself (who's resistance is/has varied from original spec) or the level sensor has developed a connection resistance or fault.
I'd look at sensor first, clean terminals at connector, then replace the temp sender .. as they are cheapest options.

There is a chance of it being the instument unit .. but unlikely.