If you pull off the hose and get a fountain of coolant, the valve is stuck open which is no real problem. If you get nothing, the valve could be working, only allowing air to escape OR stuck closed, preventing air escaping the head. A careful poke will tell you which.
Plus you may have another in the coolant hose here on the left side of the engine. Later versions ( TFs mainly) had simpler pipework, dispensing with this jiggle valve.