2000 Volkswagen Passat

Engine Cooling problem
2000 Volkswagen Passat 6 cyl Two Wheel Drive Manual 90000 miles

I have started experiencing an engine overheating problem. After driving for about 5 mins, the temperature shot to 250 and the 'stop engine' light and alarm came on. From that time onwards I had to start and stop many times until I reached home as the 'stop' and 'check coolant' alarms kept coming soon after I started. The coolant was almost boiling, but the coolant and engine oil levels are fine. An additional information - just before this problem occured, the A/C didnot start for a couple of times when I pressed the switch, although later it was working fine.
Any suugestions as to what might be the problem.
August 22, 2009.

Have you noticed the electric radiator fans coming on? If they are working then it's probably a thermostat or water pump failure.

The thermostat may have failed and stuck closed, not allowing the coolant to circulate properly.
These water pumps also have a high failure rate. The plastic impeller breaks and stops circulating the coolant.
The water pump, thermostat, and cambelt should be replaced as a set.

The A/C system is directly tied into the cooling system. So if the cooling system isn't working properly it will shut off the A/C.

Aug 31, 2009.
Thanks Dubtech for your suggestions. My problem has been solved. I was also thinking of the thermostat or the waterpump impeller, but it was neither of those. It was the faulty temperature sensor that was wrongly reading the temperature to be too high and shutting of the A/C. The mechanic thought of the sensor when he found out that the engine and the cooling system did not actually feel hot on touching. Thanks anyways.

Sep 3, 2009.
That's why I questioned the operation of the fans first. The lack of their operation affects engine cooling and a/c operation.

Glad to hear the problem was solved.

Sep 8, 2009.