The pressurestat is a CEME 5412 0.2 -6 bar ¼ inch thread, £24 from ebay. with £8 delivery…but I am sure you can find cheaper.
https://www.ebay.co.uk/itm/255459753743?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338268676&toolid=10044&customid=Cj0KCQjwtJKqBhCaARIsAN_yS_lL2GZd77jUQT04CruRbzTQ_j2TYWAuooynyGXjSfT739WhA8riZmoaAkYvEALw_wcB
The burst pressure of the stat is meant to be 12 bar, but I suspect that it’s not as high as it claims and probably lets go at 9-10 bar after repeated high pressures. basically any pressurestat that goes from min 1 bar to a maximum 8 or 9 bar bar will work, so this gives a large range too choose from.
The more modern evos use a much more expensive Swiss sensor good to 20 bar and they don’t burst, but probably retail for around £120.
The reason this one probably burst is due to the expansion valve setting being too high. You need to reduce the expansion valve setting as low as you can whilst still maintaining spring pressure to it remains pushed close. The type of expansion valve used don’t tend to be able to go below 6 or 7 bar. Without specialist equipment the best way to set it is:
unscrew all the way…while it’s open lube the O ring with Molykote 111, clean the rubber pad (give it a treat),. Then screw back to engage the threads at least 3 turns and you should be able to feel the spring pressure increase as you do so, This will be about right…but if you need to check exactly you need a pressure measuring portafilter. You can turn the preinfusion pressure up to 4 bar, use a blind filter let it fill and if you don’t see water gushing out of the expansion valve…it’s all good.
P.S It’s not about bad engineering of the machine, but a product used in many machines that doesn’t seem to really meet it’s rated burst pressure of 12 bar and my assumption that the expansion valve is set too tight…which would have been a worker issue at the factory….hopefully they are more careful now.
