The pump you are referring to is not the egr valve but the secondary air pump by the sounds of your description. You should be able to hear it slightly on startup as it takes the warm exhaust gasses and recirculates them into cold engine to help it heat up quicker to reduce engine wear. Your vauxhall one might be broken due to it sounding like a hoover as this is also a symptom of them wearing out. I would recommend just getting another one or grab one off ebay as they shouldnt be too expensive. Or you could strip it down and clean it and that might fix it.