La Marzocco GS3 Brew Pressure Always Zero When Idle

#1: Post by **jdrock** » March 21st, 2015, 2:09 am

The brew pressure is always at 0 when not brewing. Is that normal?
Once I started to brew, the pressure will climb up to 9 bar.
I tried with the blind filter and no issue with the back flush.
I remember the brew pressure will go up and down during the heating but now it is just resting at 0.

#2: Post by **caffeinezombie** » March 21st, 2015, 4:07 am

Does the grouphead leak when it is idle?

March 21st, 2015, 4:22 am

Nope. Everything just like normal.
The pressure will goes up when the pump is activated.

#4: Post by **AssafL** » March 21st, 2015, 12:52 pm

The coffee circuit has many check valves and it is unlikely all of them are stuck.

Perhaps the expansion valve is leaking, an boring is leaking or something else is leaking. Check it with the machine cold so it doesn't evaporate as quickly.

March 21st, 2015, 1:32 pm

Checked the expansion valve and the drip tray is dry. No sign of dripping everywhere.
Earlier I was using the tank for few days due to water disturbance. I noticed the brew pressure was always 0 when idle. That can be normal due to no pressure from the tank.
Yesterday I reset to plumbed in and set tank not present. The brew pressure continue to rest at 0 when idle.
Once I stopped the pump the pressure will dropped from 9 to 3 and slowly to 0. If I pre-infuse using the line pressure it will drop to 0 quickly just like released all the pressure from the group head.
Tried tighten the expansion valve and bleed the group head. Still the same.

#6: Post by **BillRedding** » March 21st, 2015, 2:15 pm

Not sure about the La Marzocco GS/3, but I thought the brew-pressure gauge on espresso machines "worked" (meaning it showed useful/accurate data) ONLY when pulling a shot...at all other times, whatever it was reading -- which could be any number, even zero -- didn't mean anything at all and should be disregarded.

Someone correct me if the GS/3's brew-pressure gauge is different than the gauges used in the more "plebian" class of machines (Vibiemme, Quick Mill, Rocket, Profitec, Izzo Alex, Faema, ECM, Expobar, etc.).

-- BR

#7: Post by **AssafL** » March 21st, 2015, 2:48 pm

Water is locked in the coffee boiler. As water expands, expander valve prevents pressure from exceeding 12 (or so) bars.

If pressure decreases, water is leaking somewhere. It might be any connection, 3 way valve, HX tube, flow meter, heater Oring, temp sensor, expansion valve or tubes that lead to expansion valve, etc.

#8: Post by **AssafL** » March 21st, 2015, 2:55 pm

BillRedding wrote:Not sure about the La Marzocco GS/3, but I thought the brew-pressure gauge on espresso machines "worked" (meaning it showed useful/accurate data) ONLY when pulling a shot...at all other times, whatever it was reading -- which could be any number, even zero -- didn't mean anything at all and should be disregarded.

Someone correct me if the GS/3's brew-pressure gauge is different than the gauges used in the more "plebian" class of machines (Vibiemme, Quick Mill, Rocket, Profitec, Izzo Alex, Faema, ECM, Expobar, etc.).

-- BR

One shouldn't read much into pressure when the machine is not pulling a shot. But in the case of a dual boiler machine water is locked in the coffee boiler and pressure usually stays high. If it doesn't it usually means there is a leak somewhere.

In the GS/3 an abundance of check valves ensure that even a pour over will lose pressure (if at all) very slowly.

BTW - I don't necessarily think this affects the cup. But a leak can have (sometimes dire) consequences if water reaches the electronics.

#9: Post by **malachi** » March 21st, 2015, 3:03 pm

Never trust any in-machine gauges. They're largely meaningless in my experience.

#10: Post by **BillRedding** » March 21st, 2015, 3:24 pm

Thanks for the additional info AND correction...

I just mentioned that point (not knowing the innards of the GS/3) because I'm more familiar (but no expert) with the "lower" class of machines, which share the "not working unless you're pulling a shot" brew-pressure gauges.

For specific example, my Vibiemme Super HX Owner's Manual states:

"Brew Pressure Gauge: The information that this gauge displays can actually be confusing. This is because it is reading the pressure
inside of the Heat Exchanger. When the machine is at idle (or actually at any time other than when brewing
espresso) the readings of this gauge should be ignored. Its only function is to report brew force and at any other
time the reading is not reporting anything of note at all.
During the brew cycle the reading should be in the range of about 9 to 9.5 bar if everything else is correct."

...so I guess it's only an HX-machine-thing, if you will, and doesn't pertain to a DB.

-- BR