Overheating-help!!!!

We have a base model 2003 automatic VW Beetle. It was fine and driving 2 days ago. It has been sitting without use for 1.5 months awaiting my 16 year old getting it on the road. We took it out for the first time and it was fine. We took it into our mechanic to have new brakes put on and the oil changed. When we picked it up to coolant light began to flash. Despite this she went on her way on a 20 minute ride. When she arrived it was found that she needed coolant desperately. They filled the collant resevoir. By the time she made the 20 minute drive home the coolant in the resevior was boiling and smoking. I left the hood open all night for it to cool down. When I looked in the morning there seemed to be no coolant left, so I refilled it and made my way to the mechanic, 2 miles from home. By the 1 mile mark the coolant light went back on. They checked the head gaskets and they are fine. They have replaced the coolant temperature sensors and the thermostat and it is STILL overheating. They are at a loss. What else can it be?

leak in the cooling system somewhere.

have it pressure checked. look for loose hoses or leaks somewhere.
if you have steam coming out the pipe your headgasket is the problem.

are your fans coming on when your at a dead stop or parked with engine running? that could be it too.

We have a base model 2003 automatic VW Beetle. It was fine and driving 2 days ago. It has been sitting without use for 1.5 months awaiting my 16 year old getting it on the road. We took it out for the first time and it was fine. We took it into our mechanic to have new brakes put on and the oil changed. When we picked it up to coolant light began to flash. Despite this she went on her way on a 20 minute ride. When she arrived it was found that she needed coolant desperately. They filled the collant resevoir. By the time she made the 20 minute drive home the coolant in the resevior was boiling and smoking. I left the hood open all night for it to cool down. When I looked in the morning there seemed to be no coolant left, so I refilled it and made my way to the mechanic, 2 miles from home. By the 1 mile mark the coolant light went back on. They checked the head gaskets and they are fine. They have replaced the coolant temperature sensors and the thermostat and it is STILL overheating. They are at a loss. What else can it be?

The impeller on the waterpump is made from plastic and must be replaced every 60000m/100000km otherwise they will and do fail. The blades break off and it wont pump water resulting in no cooling. It is also usual to replace the timing belt and adjuster at the same time.This is fairly common unfortunately.

oh wow, I never knew they used plastic water pump fins! how stupid!

Look under the radiator to see if water is leaking or dripping from underneath. There is an overflow valve that may be leaking around the gasket and it would need to be replaced. That's what was wrong with mine.