Tempratute Cauge problems

[Anastasis]

Hi to all!
I have bought a BMW Z4 coupe 2006 model, about 2 months ago and I am facing some problems with the heating indicator.
After I am driving the car for more than 20-30 min, (all the times happened in highway with speed more than 120 km/hour) suddenly the temperature needle goes to red with a beep. I stop the car for 1 min., switching off the engine and after I switch it on again, the temperature is back to normal.
The engine temperature seems normal, I even was possible to open the cap of the fridge and of course the water was not boiling, it wasn't even hot actually, as I put my finger in it.
The problem doesn't appear when the car is on idle for a long time (10-20 min) even with the AC on.
So I suppose it could be the thermostat or the electronic water pump.
(I went to Munich Motor Works and said that the diagnostic said it is a faulty electronic pump, suggesting to change it with the thermostat, although they didn't provide me the print out from the computer diagnosis.)
Anyone having the same problem as well and any possible solutions?

 

[Steve84N]

Sounds more like the thermostat than the pump as you'd have killed the car by now if it was the pump plus it's not cycling the hot coolant around the system. Mine overheated much faster when the pump failed. Have a search for the bleed procedure for the pump, some sequence of ignition key and button pushes or something, then listen to see if you can hear it working.

It's less work to just change the thermostat but if the pump hasn't been changed it's worthwhile doing anyway as they fail. Mine is a 56 Coupe and it died at 50,000 miles or thereabouts. Main difference is the extra few hundred pounds to buy the pump as it's electric.

I'd take their advice and change both, I didn't do the thermostat and wish I had now for extra peace of mind.