La Marzocco Linea Mini – 12 Monthly PM – DIY Guide

INTRODUCTION

The LINEA MINI is a top of the line domestic coffee machine, with twin boiler PID temperature control. I do not see them often, this one came in from a regular customer for it’s 12 Monthly PM. La Marzocco have a 13 point 12 monthly service plan. As I was new to the machine I thought i would go over this service and make it easy for the next one and tell you where to find everything and the easy way to do it, I’ve just done it the other way so you don’t have too.

The Service Points as stated by the Italians

  1. Replace Group Gaskets (not difficult so not covered here)
  2. Replace diffuser Screens (not required)
  3. Replace Porta Filter Baskets (not required)
  4. Inspect Group Valve (will do)
  5. Clean Restrictor (will do, once I find it)
  6. Test all Switches (stop trying to be German)
  7. Test Flow Rate (will do)
  8. Test Brew Temperature (will do)
  9. Test Brew Pressure Setting (Visual Check on Gauge with Blind Filter)
  10. Clean Water Level Probe (yes will do)
  11. Replace Steam Boiler Vac Valve (no but we will inspect it)
  12. Replace Pressure Safety Valve (yes if it needs doing)
  13. Inspect drain system (yes ok)
  14. Test Pump capacitor, this is my addition but if we are going to be wanky then why not.

GETTING INTO THE MACHINE

This is easy when you know how.
1. Remove the Top Panel
2. Remove the Front Screws
3. Unscrew and remove the PID Knob as it will be in your way.

lineaminiscrew

4. Undo 2 screws inside the machine that hold the back panel on and slide the side assembly away. You are in, it’s naked!

GROUP VALVE INSPECTION
This is the 3 way valve located on top of the main boiler in the middle. I removed the coil and and then the stem and plunger. if they had been fouled with coffee oils I would have soaked them in a suitable agent or bicarbonate of soda.

TEST FLOW RATE
According to LM, the flow rate (water through group) should be 400mls in 30 seconds, this is with the standard sized restrictor 0.8mm. The flow rate can tell us if we have restrictions (scale) within the Hydraulic system, so its an excellent indicator of system health. A measuring glass and a timer are required.
I measured this one at 188 mls in 30 seconds. SCALE!

CLEAN RESTRICTOR
Its common for the restrictor in the flow meter to scale up, inhibiting water flow so that’s where I will look for the cause of the low flow rate. I know scale is an issue with commercial La Marzocco machines in the restrictor in the flow meter. But finding the flow unit in this machine was difficult as it does not have one. No need as there are no programmable shots. So where is the restrictor?, its part 22 in the diagram below, just before the 3 way valve.  Not too difficult to get at, in theory. In practice I had to remove the complete valve. A right pain and it was very restricted.

TEST FLOW RATE
According to LM, the flow rate (water through group) should be 400mls in 30 seconds, this is with the standard sized restrictor 0.8mm. The flow rate can tell us if we have restrictions (scale) within the Hydraulic system, so its an excellent indicator of system health. A measuring glass and a timer are required.

CLEAN WATER LEVEL PROBE
The Probe is hard to get at without the sides removed, but it can be done. As I did it. As usual once removed, clean off scale and corrosion with a wire brush. Sometimes with very acidic water it needs to be replaced. This one was not bad. Call me old fashioned but I use a little thread tape on the probe thread.

TEST BREW TEMP
I used an accurate digital thermometer. I found the temperature adjustment very stable and accurate. I preheated the Portafilter and removed the basket and measured the water stream. I got a range from 82’C to 99’C and found it easy to set it precisely at 91.8’C. It should be noted the steam pressure on this machine is set to 1.7 to 2 Bar.

That’s all Folks! – yeah there is more but I was getting bored with this.

Find Parts For Traditional Coffee Machines Here

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