Jomo Senior Member Joined: 8 Jan 2014 Posts: 7 Location: Washington DC Expertise: I like coffee
Posted Wed Jan 8, 2014, 2:08pm Subject: Breville BES900xl Repair
I've got a BES900xl that is sort of working. When it first came into my hands it had no pressure at the group head. I took it apart and found the OPV spring was missing and have since fixed that. That got it working. (all the pressure /water was just going out of the OPV release)
The trouble now is when I pull a shot I sort of get a shot but it trickles into the cup very slowly about 60 seconds to do a double shot with single wall. The pressure gauge is reading ~9.5 bars. The intersting thing is the gauge reading depends on how hard I tamp. The last shot I pulled I tamped probably closer to ~30lbs and the gauge read ~11 bars. So I'm wondering what is up. Most importantly it just doesn't seem like a proper extraction is happening. I tried running a cleaning cycle with a cleaning tablet and didn't seem to do much.
It appears if I tamped too hard it would take over a minute to get a shot out of it. Anybody have any ideas as to what I should look into? I've taken this thing all apart so I've got no problem looking at the mechanics of it...
Ok, so I've made some diagnostic progress. I've found if I close off the return pipe it increase the pressure and flow at the head while pulling a shot. It seems to fix the amount of time it takes to pull a shot though the gauge is reading into the ~13-14 bars. I'm not tamping too hard and the grind isn't insanely fine. Either my OPV is bad or there's pressure leaking somewhere....
Your target pressure should generally be in the 9.0-9.5 BAR range. Sounds like you should use less ground coffee or coarsen the grind a little bit as a test. Also fresh beans pull very different from stale, so you'll want to test with some fresh roast coffee too.
Yea, I ran a cleaning cycle and made no difference. I did try less grind and coarser grind and it did make a slight difference. I think the real problem is some sort of blockage dealing with the water flow to the group head. Temperature is fine, pressure is fine, the pumps are fine, I think because of adequate pressure.
So I think I've isolated it to something to do with the water flow line. I'll double check the shower head but I'm pretty sure its A-OK.
Check what happens if you remove the screen and dispersion disk and do manual flushing. If you still don't get enough flow, then check for any obstruction in the group head channels. Maybe you can blow it out with compressed air or remove it with piece of wire. It might be piece of scale or broken o-ring. See the o-rings condition in this post: "Breville BES900 hydraulic diagram + some technical details" They were very brittle and there was a lot of scale around them.
Thanks for that link witoldb. I've actually taken the 3-way solenoid valve off and it had some scale build-up but nothing crazy. Also it had a gasket and no o-rings. The gasket was in good condition. I'll dig a little more into it tonight after work.
So I blow air into the spout hole (where the porta filter goes) and I only get air coming out of the tube for the pressure gauge. I get no air from the tube for opening for the boiler. I'm trying to check for any sort of blockage. I don't quite understand the water flow and what pipes do what.
I suppose the most important question is where is the water coming from that makes the espresso shot? So I can check for proper pressure and flow on those lines?
OK... I just have to say.. I win the award of the year for makingg things way more complicated than they really are. So I finally picked up the manual and read that when in manual mode you press the manual button for infusion time and then release it to pull the shot. What I've been doing is just pressing the manual button like a flip switch.
What's been happening is it is pulling the shot in pre-infusion mode. WOW. Well atleast I now know how to take this thing apart and put it backtogther.. GEEEZ!!!
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