I think you'll find this is a difficult question to answer off the cuff and really does require the machine sitting on the bench in front of you (me/whoever) for a proper diagnosis. Certainly if the safety valve blew off a couple of times, then it appears the pressurestat was not switching off rather than that the safety valve is somehow faulty. If you fit the spare safety valve, and the problem lies elsewhere, it should do the same (blow off). Also if it blows off continually then you might guess that there is a piece of crud stuck in the seal allowing a continual leak in th valve. But if it blows off thereby decreasing the pressure, but blows off again after a short time, then that would point me back to the pressurestat. Whatever you do, I would recommend NOT disassembling the saftey valve except if you count the exact number of turns to screw out, and after inspection/clean, you reassemble to the exact number of turns. This is so it will blow off at the same pressure as it was set during manufacture. The biggest problem would be where someone doesnt assemble it back to the same blow off pressure and ends up with a much higher setting....turning the boiler into a nice bomb. Safety first, anyone not feeling competent should leave the valve well alone. Also of course, remember that getting into an espresso machine means playing with an electrical device which is very dangerous and could be fatal. Switching off the power point is NOT GOOD ENOUGH. Always pull the plug right out of the socket before doing anything. Hope that helps. EDIT: thinking on your comment "...I wont leave it on...". Over a period of decades, I have been a staunch proponent that you DO NOT leave espresso machines on willy nilly if they are actually not in use / for which I have copped plenty of flack from keyboard know-alls that know better than experienced people that work in coffee and equipment business (had to get that in ;D ). My advice is: In home use, switch it on say 20 min before you want to use it, and unless you know you are going to go back within a short space of time to make more coffee...switch it off. Just switch ion again before the next sitting. heat exchanger machines are designed for CONTINUOUS USE. Home use is not continuous use, and the machines dont just overheat tremendously if they are left on without use causing large cooling flushes and wastage of water (certainly if you are on tank water), before next use, but they are cycling and wearing out the components even if they are not being used to make coffee. The component to wear out quickest in a machine left on indefinitely (without actual use), is the pressurestat. Small machines with home use (micro sized) pressurestats fitted, will easily wear out a pressurestat in 12 months when left on 24 hours a day, (again...regardless that they are not in use making coffee most of that time). The fix is: a) when replacing micro pressurestats ask (and expect to pay more ) for the better quality units and b) dont leave machines on when they are not in use. Not saying you do that Lacehim, this is just a general bit of advice to the readers.
