My new to me NS Oscar has been a work in progress. Recently replaced the pstat with a Sirai. Fixed one problem. I then probably somewhat foolishly experimented with the brew pressure by adjusting the "non-adjustable" expansion valve, knowing that the consequence would be some additional water into the drip tray.

I tightened it back up all the way, but still get the same amount of water dumping. Here's video:
I assume it either needs to be replaced or repaired. I hate to take it apart and have no espresso while waiting for a part to arrive since it still makes a decent shot.

thanks, Daran

expansion valve is set to release at 16 bar of pressure
be very careful removing and installing valve into the group head , there are only 3 or 4 full threads and a casting ridge on the group head where the valve seats
plus it's prone to leakage , thread sealant advised

however you could shim the spring to get the silicone plug to seal on the interior seat
removing any build up on the seat might restore sealing function

gluck

Thanks for info. I removed it and disassembled. It was already pretty clean from all the cleaning and descaling I had done previously, gave the valve a citric acid bath anyhow. There didn't seem to be any damage to the seal. Re-assembled and installed, no leaks - but still dumping out a lot of water. May try to shim the spring next as you suggested.

I'm thinking about adding an opv on the cold water side soon, maybe that will keep this expansion valve from opening, and maybe it won't if it's faulty. I think I just talked myself into replacing it anyhow, if I'm going to be ordering parts soon anyhow.

Thanks! Daran