Alfa Romeo Brera 2.2 JTS coolant temperature issue .

[Pigs lips]

Hi I recently won this lovely car on eBay for silly money it's been laid up for three years due to strange overheating issues, it runs fine the fan cuts in at 90 degrees and cools it down while it's ticking over but when you drive it the temperature gauge drops to zero and the heater blows cold it's not losing any water or boiling up there's no mixing in the header tank or sump it's clear on the sniff test no air locks the thermostat has been removed and the water is circulating I'm thinking that it could be a water pump issue or a hose collapsing when the engine is under load. Any advice would be gratefully received