Disappearing Coolant

How can it be that my coolant resivoir runs empty every time I fill it up, but my radiator isnt losing ANY coolant. The resivoir has been empty for over a week and the radiator remains full, no problems at all. Once i fill the resivoir back up, it will do the same thing again. There no leak in the resivoir so I dont know what it could be.

Odd, I would fill it then let it run for a while check for leaks. Maybe it is only loosing coolant under pressure?

Check your coolant hoses, it could be seeping from there, ends may need to be tightened…had that problem in the past. Its not normal for the resivoir to be empty so soon. HTH