Help! La Marzocco Linea Mini brew pressure troubleshooting

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#1: Post by cherns »

Hello! I'm new to HB and was hoping to get some help and insight on a problem with my 6 month old LMLM that I'm using on reservoir.
There was an initial issue with a low flow rate, but the local agent fixed that by clearing out the orifice. However after he re-assembled the machine, the brew head pressure gauge now indicates 0 pressure on idle.

When pulling a shot, the brew pressure gauge goes to 9 bar, but after disengaging the switch, there is a lot of overflow at the bottom, as well as a bit more water dripping down from the brew head - as though it's not quite able to close off completely. The agent hasn't had any success in figuring out what went wrong.

Anyone have a similar experience or know what might be the issue?

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#2: Post by Jake_G »

Hi Chernwei,

Welcome to HB!

It sounds to me as though whatever blockage was in your orifice has also gotten into your 3 way brew solenoid and is preventing it from sealing against the pressure in the integrated brew group (IBG). The solenoid is oriented horizontally, so some of the water drips out the exhaust tube, and some drips out of the group. The solution is to remove and disassemble/clean the brew solenoid and reinstall.

It is not an terrible job, but there are some tubes that need to be removed and it is tight back there. Here is a drawing from the parts manual:

You have to remove the pipes labeled 16 and 19 and then unscrew the solenoid from the IBG to clean it out, stop the leak and restore the typical idle brew pressure.


- Jake


#3: Post by cherns »

Thank you kindly Jake! Will get it worked on this weekend and post the results here :)


#4: Post by cherns »

Did a quick video of the issue. Apart from the gauge movement, you'll notice that after a few seconds from closing the switch, there is some extra water dripping from the grouphead. Not sure how to use the Youtube function here... apologies if it doesn't embed properly.


#5: Post by Jb3 »

I had a similar issue with my Linea Mini. I had a constant drip in my drip tray and the brew boiler wouldn't hold the 12 bar pressure. A few things I did was unscrew the expansion valve (part #4) and made sure there was no scale build up. I also replaced the solenoid plunger that I read gets warned out after time. My LMLM is 3 years old and I figured it wouldn't hurt to replace. After doing this, the brew pressure issue and drip were better but not completely resolved. I'm not sure if the orientation of the plunger matters but once I reoriented the plunger with gap facing the back of the machine, the brew pressure issue and leak were both resolved. It could just be that the plunger made a better seal. It's very easy to disassemble the solenoid to get to the plunger. Hope this helps.


#6: Post by nuketopia »

Yeah, that ain't right. Your tech needs to come back and figure out what happened.

There are a number of things that could be wrong. If he removed the brew orifice, he probably had to open the top of the brew boiler. There is an expensive seal (big o-ring about $50.00 US) that seals the top.

The 3-way solenoid valve could be clogged, since that's where the water goes after the orifice. It has a tube that relieves the brew pressure into the drip tray.

There is a relief valve that regulates the standby pressure to 12-bar that leads down to the drip tray. It's mentioned in the owner manual. It could also be plugged open with whatever clogged your orifice as well.

Pull the drip tray out and use a mirror and you'll see three things that drip into the tray right at the center. One is a plain tube, that's the steam from the vaccuum breaker for the steam boil. There's an aerator just like the hot water wand, that's where the 3-way solenoid valve discharges when you stop brewing. Then there's the bottom of the 12-bar adjustable valve, it's a big brass thing.

Look and see where it is dripping.


#7: Post by cherns »

Update: seems like the dripping was resolved after adjusting the expansion valve. However, the brew pressure still registers 0 on idle. Anyone have any ideas?

Edit - will try replacing the gicleur tomorrow and see if it fixes the problem.


#8: Post by nuketopia »

I think your technician broke something else while repairing it. Something is leaking. It should hold pressure a long time if it is working properly.


#9: Post by cherns »

Bingo. The plunger was damaged and no one noticed!