My 16 month old (from new) 17k miles Astra J 1.4 Turbo has started consuming coolant. The first time the warning "check coolant" came on I filled the header tank exactly to the max line, but it was all consumed to the min line and the warning was back after a week.

Took it round to the local suppyling dealer who tested the compressions and pressure tested the cooling syastem and declared nothing wrong. They overfilled the header tank to about half an inch from the top but six weeks later and c1500miles its back down with the warning on again.

The excellent local Autocentre have looked at the car and can find no visible leaks, but say there is a slight gassyness in the header tank when the engine is hot and cooling fan is running, suggesting that the head gasket on the way out.

There does not appear to be any water in the oil and the (pink) antifreeze in the header tank is completely clean. Any ideas? The car goes back in next week but I'm not optimistic about the outcome. Is it acceptable for modern engines to use coolant? Until now I've been very happy with the car.