Posted Sat Nov 16, 2013, 7:27pm Subject: Starbucks Barista/Saeco Aroma boiler not sealing
I'm new to the forum, but a long time reader of the site.
I have endeavored on a repair of my beloved starbucks barista home machine and hit a roadblock- I'm hopeful someone can help me out-
Background: I've had the machine 10 years, and it has seen routine use. I formerly lived in southern california, a region known for it's hard water (see below). During a routine cleaning of the machine, I removed the grouphead screen, and upon reassembly, the brass "mushroom valve holder (part D2-45) " became stripped. I ordered a replacement (stainless steel, from Stefanos), but could not get it the original brass one to unscrew from the boiler with the machine assembled.
As such, I extracted the boiler from the machine, but could in no way manage to get this piece out of the boiler - possibly bonded to the boiler due to the very routine use of filtered hard water- and using a bolt extractor was a complete failure due to the soft brass material.
Since I already had the boiler out, I ordered a new lower boiler and mushroom valve assembly (new boiler o-ring also). Today I replaced them and reassembled the machine, but am having trouble obtaining a seal under pressure, and I am wondering if there is some sort of trick to this?
The machine turns on and heats up just fine without a leak, and holds a seal fully up to temperature in the steam-mode also. The problem arises when the pump is turned on to brew espresso-
Before it can overcome the seal of a pressurized handle, it begins to spew water from between the plates of the upper & lower boiler halves. I also depressurized the handle, fearing it had become gummy after spending a month sitting dry for the first time in it's life. With this depressurized handle, it begins brewing espresso just fine, but about 2/3 of the way through pulling a shot, it begins to leak through the boiler as stated above.
I've completely disassembled the machine, checked the o-ring placement to make sure it didn't get wonky during assembly, and reassembled the machine to no avail. It still leaks while brewing. I additionally tightened the boiler assembly bolts with the system at brewing temperature - rationale being that the bolts are lengthening as they expand upon heating - so I am sure the system is at maximum tightness.
What's obvious is that the seal is presssure-limiting the system. will it help at all to "grease" the gasket? any "food safe" grease I can imagine (crisco, butter or coconut oil?) would liquify at brewing temperatures and thus not assist in obtaining a seal.
Any insight that might direct me toward obtaining a good seal on the boiler would be appreciated.
Also, I'd like to ask a question about the overpressure valve (OPV) attached to the pump - could it be, that the seal I'm obtaining is just fine, but the system is becoming over-pressurized? The OPV is not opening at all under the testing today (I'm running it without the back plate/cover on so I could investigate the source of the leak). Should this be opening at all under normal use?
I ask because I was unaware that the system had one: about 8 years ago, the portafilter became >90% clogged (before I knew they needed to be painstakingly cleaned with a needle once every blue moon) and the system would not brew with finely ground coffee- During this experience, I would set it to brew, and the pump would go for about 20 seconds until it eventually stalled out due to the high pressure of the system- pretty sure it wasn't the heat-switch on it turning it down because I could bleed pressure from the system via release out the steam wand and this would allow the pump to immediately start pumping again. This tells me that the OPV was never opening; or my pump was too weak to over-ride it.
Posted Sun Nov 17, 2013, 11:10am Subject: Re: Starbucks Barista/Saeco Aroma boiler not sealing
That is correct. 62 is the OPV/safety valve. I was wondering if water is ever supposed to flow out of this valve under normal operation?
And, thanks for the links, it is great that these resources exist on the internet - the teardown at ifixit enabled me to attempt this repair.
I was pretty careful to tighten the bolts in an opposing pattern similar to the way you tighten a four-lug wheel on a car. I'm at a bit of a loss as to what else can be done. The only thing I can think of is that the bottom boiler half is slightly bent and this is compromising the seal.
I emailed Stafano through his website for any advice, and will follow up here with any words of wisdom that are bestowed outside of the forum.
Posted Sun Nov 17, 2013, 11:08pm Subject: Re: Starbucks Barista/Saeco Aroma boiler not sealing
Sorry that I did not see this earlier. The safety valve is a form of non-adjustable OPV. I do not know the set point, but it is to prevent pump damage. In machines shipped with pressurized PF's the setting is high enough to allow for the high pressure associated with pressurized PF, say perhaps 12 bar. Unless you near choke the machine, I doubt much flow back, but it is set to allow it. Some valves with springs or o rings are more leaky with age and may some back flow, but then the system may not develop full pressure needed. With an adjustable OPV, most set for 9 bar at the puck, so the valve allows for backflow when 9 bar is reached.
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