If the machine had a functioning pressurestat, there should be no need for a wobbler weight, but some still have them as a safety feature. The valve you have pictured is a standard safety valve, which has a spring and a teflon seal normally. You can just replace the spring and teflon seal, but most people just replace with a new valve - Note ; gaggia use a 19mm safety valve, not the more common 3/8"
