Hello everyone, been a 10y+ long time lurker and finally created HB account (paranoid about spam). Anyways, I think I already know the possible fix, but wanted to run this by all you experts before attempting to fix.

Machine: Isomac Tea HX
Regular backflushing done weekly, and with detergent monthly.

Symptoms: After pulling the lever to activate the brewing, I begin to steam milk. On average, steam pressure will hover between 1.1 to 1.2 bar when I've done this in the past. Recently, the steam pressure begins to lose pressure and go down to about .5 bar, which pretty much eliminates the function to steam and brewing at same time.

Self diagnosis: I think there could be 2 possible issues: (1) Small leak in the HX chamber which is releasing cold water into the boiler causing boiler to lose pressure OR (2) Solenoid valve is not fully closing(maybe scale buildup?), therefore releasing cold water backwards into the boiler.

What I have done so far: Full descale of machine. With the descale solution, I made sure to run the pump to backfill the boiler in order for the descale solution to flow through the Solenoid valve. I have done this about 6 times on day 1, then let descale solution sit in boiler overnight, and ran backfill again 6 more times on day 2. After everything was cleared out, the symptom is still there.

So I plan to buy a replacement solenoid valve, but I am worried if that doesn't solve the problem, I may have to invest in a new boiler? So instead of possibly wasting time and $, I wanted to pick your brains to see if there are other methods I can try to pinpoint exactly whether it is a bad solenoid valve or leaking HX boiler? Or maybe I am completely off then someone can point out another possible issue?

Thanks in advance to everyone!

shotkall3r wrote:(2) Solenoid valve is not fully closing(maybe scale buildup?), therefore releasing cold water backwards into the boiler.

So I plan to buy a replacement solenoid valve, but I am worried if that doesn't solve the problem, I may have to invest in a new boiler? So instead of possibly wasting time and $, I wanted to pick your brains to see if there are other methods I can try to pinpoint exactly whether it is a bad solenoid valve or leaking HX boiler? Or maybe I am completely off then someone can point out another possible issue?

I believe you're probably correct. Your boiler fill valve is leaking internally, allowing cold water from the high pressure brew circuit to escape into the low-pressure steam boiler. Thus, your boiler is badly over-filled leaving only the smallest pocket of steam above the liquid and the steam will run out quickly.
You might be able to further prove this by running the brew circuit against the blind filter and watching the steam gauge, if it climbs quickly above the 1.4 bar mark, you know the brew water is flowing into the boiler and pressurizing it.

Before buying the new one, you might want to just dis-assemble, inspect, clean, reassemble and test the existing one.

Do you think/feel the water at the group head still at same temperature as before ?
Any chance that the pressurestat does not perform well?
Even at the very first daily activation it stuck at 0,5 bar?

You might be able to further prove this by running the brew circuit against the blind filter and watching the steam gauge, if it climbs quickly above the 1.4 bar mark, you know the brew water is flowing into the boiler and pressurizing it.

Before buying the new one, you might want to just dis-assemble, inspect, clean, reassemble and test the existing one.

Running blind filter, steam gauge stays at 1.3 to 1.4 bar and doesn't really move. I did this several times for about 20s each time. Also, forgot to mention, I previously dis-assembled the solenoid valve and could not see any blockage or scale, although keep in mind the solenoid coil(black square box) cannot be removed from the valve body so I could not really see inside. they are are 1 piece on my machine.

Do you think/feel the water at the group head still at same temperature as before ?
Any chance that the pressurestat does not perform well?
Even at the very first daily activation it stuck at 0,5 bar?

The group temp seems normal. Still keeps consistent temp at group head when left on all day. I think pressurestat is OK, because when I steam, WITHOUT brewing, the steam will stay consistent at 1.1 to 1.2 bar. The steam only falls to .5 bar when I steam AND brew at the same time.

Basically at this moment, my HX machine is being used like a single boiler. Only 1 function (steam or brew) can be done but not at the same time.

Thanks for your replies, keep them coming if you have any other theories/diagnosis/etc....