If water bottle is full to start with then becomes empty then there must be a leak unless there was an airlock in the cooling system.
If there are no visual leaks from hose pipes or under the car then the water must be going into the combustion chamber.
If this is the case you will notice white smoke (steam) from the exhaust tail pipe even when the engines warm and has covered a few miles.
OR
The water is leaking into the sump (engine oil) in which case you will see white (salad cream) substance under the oil filler cap and small water dropletts on the dipstick.
The cause of this is a failed head gasket. Take it to a garage / repair man and get them to do some pressure checks on the cooling system / sniff test to see if exhaust gases present .
Also check water bottle / expansion tank filler cap pressure test and seal condition.
Maurice, December 2010
