Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

First I would look to replace the gasket washer under the safety valve, and/or perhaps wipe it with just a bit of steam oil to help it seal better. The stem of the relief plunger on the safety valve will also benefit from a small drop of steam oil to help it seat and seal. I don't recall offhand if Wilesco safety valves have any o-rings or other seals, but if so, replace that too. Usually there is a cone shaped "seat" that the spring pulls the stem down against for a seal, so be sure that both of those surfaces are free from dirt and grit and seal properly from ample free moving spring pressure. If the spring seems too weak, you may want to replace that, but it really shouldn't be very strong. If it still leaks steam before getting up to pressure, then replacing the entire safety valve may be a good idea.