So I went on an extended trip where I was gone for nearly two weeks. I made sure my machine was backflushed and very clean before shutting it down and leaving on my trip. Normally it's on a timer where it sits idle 10 hours out of every 24 (Midnight-10AM). I came back from my trip, turned it on and had no issues for two days, pulling perfect shots on the first try with some defrosted coffee. I then left town for another four days, again shutting the machine down. After coming back, the machine works fine, but now my vacuum breaker hisses and sizzles softly, but constantly. Normally it only does this when the machine is coming up to temperature, but now it does it nearly constantly. The autofill also seems to be kicking in a lot more often too, for what that's worth.
My theories are:
-Dried scale on the valve, preventing it from forming a decent seal
-Dried scale on the fill probe, preventing it from accurately signaling the autofill to stop
-PSTAT has gone out of adjustment
I have the Oscar, but thanks to Plindy, it's more Musica now than anything else. Does anyone have an idea of where I should start? Everything has been completely descaled less than four months ago.
The autofill is kicking on more often, because the vacuum breaker is leaking steam (gaseous water), that as is generated from the water in the boiler, so if your constantly using is, of course the autofill will come on more often.
The is a way to clean the vac breaker, if it is the pin type. Remove the top, get the machine up to temperature, with the end of a long wooden spoon, press fully down on the pin at the top of the vac breaker for about 3 second, release await and repeat. This may well steam clean the seat and cure the problem.
However, it may not be the vacuum breaker, so visually confirm that it is indeed the vacuum breaker leaking and not the safety valve.
physicsdude Senior Member Joined: 18 Feb 2008 Posts: 41 Location: British Columbia Expertise: I love coffee
Espresso: Expobar Office Lever Grinder: Compak K3 Touch
Posted Sun Jun 2, 2013, 4:13pm Subject: Re: Leaky Vacuum Breaker
I found this thread when my vacuum breaker started acting up the other day (Expobar Lever HX machine). Cleaning didn't help (made it worse) so I have ordered a new one. In the interim, I did a nice fix on mine though. I took apart the breaker again and removed the white nylon plug. I cut a short piece of surgical rubber tubing to replace it (about the same diameter, thick-walled type), and reinserted the brass stem with the small o-ring and put it back together. It works great- so I am able to use the machine while waiting for the real replacement. It does allow the pressure to bleed down after turning off the machine, as well as hold the pressure while it is on.
His breaker is new, but I guess faulty. I had to tighten up some stuff after the tear down and I just started hearing a new hiss. I guess I need to find it. It is very hard to see and track them down. Anyway, he is a student and probably busy this time of year.
Buying advice: GRINDER GRINDER GRINDER. Don't cheap out on the grinder.
As I remember after watching the video, LOXEAL was used throughout during the modifications, but this same fault can happen if using teflon tape on a new vacuum breaker. Sometimes tape can get extruded out of the threads ahead of the fitting and blow back up through the valve, causing it to get trapped between the o-ring and its seat. This will cause even a brand new valve to hiss. I use LOXEAL or a copper crush washer on the vacuum breaker to prevent this issue.
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