Further to TCF's reply bellsux, the squibs (cartridges) have a shelf life and an inservice life. I think the bell kits require the sqibs to be blown at a certain interval after fitting (read the applicable service instruction). The bottle maybe due for hydrostatic at the same time.
This does check the whole system but then a new cartridge is fitted with a refurb kit and costs at least a couple of grand.
