How to Break a Glued La Pavoni Pressurestat

#1: Post by **drgary** » October 25th, 2013, 2:07 am

Sometimes you learn how not to do something by breaking it. Luckily this was an inexpensive part. My 2002 La Pavoni Europiccola Millennium model was running too hot for the past couple of months. I tried to resolve this by descaling it with vinegar, using Robert Pavlis's method of powering on, bringing the machine up to pressure, powering off and repeating that several times. The temperature soon after startup did decline by about 10 degrees Fahrenheit when measuring the outside group temperature. However the machine would still idle too hot after awhile. So I went into the base and thought I might adjust the PSTAT (pressurestat). Here is what I saw:

I read in another thread that the knurled ring is for adjusting pressure and that this is sometimes glued in place. Well yes, it would not move. So I tried to turn it with pliers, and this is what happened:

Others have tried to free these using a hobby knife to loosen the ring from the "glue." Stefano at Espressocare.com tells me that this is paint applied by the factory and that at this point the PSTAT is broken.* The white spot on the threads is where the paint was applied.

Fortunately I had a spare, almost new Mater PSTAT from my recent Cremina parts machine purchase. The seller gave me a vintage Olympia Express PSTAT I revived and installed on the Cremina. But the Mater PSTAT works perfectly in the Europiccola and has an adjustment screw. So this repair fumble cost me nothing.

I'm sharing these photos so others know the plastic adjustment ring on these glued PSTATs are fragile. They really do need to be freed with a hobby knife.

After removing the broken PSTAT I inspected the fitting and discovered that descaling was still the best way to go. There is still some nasty scale in there. If I had to do this again I'd removed the PSTAT, prop it with the fitting upright, fill it with vinegar and let it sit for about an hour before rinsing it with fresh water. That's how I revived the Olympia Express unit.

* I tried to disassemble it later to see if I could fit a substitute nut on those threads. I could not find a way to take it apart, so it went in the trash.

#2: Post by **algue** » October 25th, 2013, 5:48 am

I also have that pstat in my 2003 pavoni pro.
When I have to adjust pressure I simply turn the "screw" visible in your second photo on the bottom-left side.
I never had to remove the glue from the ring.
Alberto

October 25th, 2013, 8:03 am

I recently came across a similar scenario but not on an espresso machine. My pool heater has a similar looking pressure switch and the adjustment ring was glued. Seems they don't want you to mess with the adjustment. I also had to break the glue apart with a utility knife. Live and learn.

#4: Post by **rpavlis** » October 25th, 2013, 9:46 am

When things break it generally makes good sense to evaluate the problem to arrive at the most sensible repair. Often the reason things break is because the OEM part was badly designed or defective! It may make sense to replace it with similar higher quality part. If one have access to any kind of shop tools, it often makes sense to consider making a replacement of higher quality than the original. One can often do things like that with nothing other than a few taps and dies, a good hacksaw, and power drill. It is worthwhile to think about the action a bit before charging into it because a better solution might come to mind.

I suspect the replacement pressurestat was better than the original so that the machine is better than when it left the factory.

(In fact OEM equipment often has parts so defective that it makes sense to get rid of them before they have a chance to break!)

For a non coffee example, I broke the mounting saddle from an equatorial telescope mount a few days ago. It is a much better mount now than it was before, because the OEM design was poor. It has an entirely different saddle now. (It did not break, however, because of the poor design, it broke because I dropped it!)

October 25th, 2013, 10:41 am

algue wrote:I also have that pstat in my 2003 pavoni pro.
When I have to adjust pressure I simply turn the "screw" visible in your second photo on the bottom-left side.
I never had to remove the glue from the ring.
Alberto

This is good to know. Who would have thought? The amount of scale still in the PSTAT would still have made it malfunction again, so removal and a vinegar infusion would have been the most lasting fix.

#6: Post by **TomC** » October 25th, 2013, 10:54 am

It would be nice if the adjustment screw mentioned was actually located in an accessible area, i.e., facing out when the cover is removed. It doesn't appear that the Pstat can be rotated 180 degrees in its position now, since it's so close to the wall.

#7: Post by **allon** » October 25th, 2013, 11:23 am

drgary wrote:
* I tried to disassemble it later to see if I could fit a substitute nut on those threads. I could not find a way to take it apart, so it went in the trash.

Fish it out of the trash and try the following:

Wrap the threads (and surrounding area) with Teflon tape.
Knead some epoxy putty to activate it and make a ring over the threads. Squish it in good, then sculpt the ring so it will not hit any parts of the pstat that it should not; sculpt it to make a good shape and let it harden.

Once it is hardened, it should turn - the epoxy will not stick to the Teflon. I've used this trick to cast replacement threads in the past, though not exactly the same application.

#8: Post by **homeburrero** » October 25th, 2013, 1:22 pm

allon wrote:Fish it out of the trash

If not to repair, perhaps to tear it apart out of curiosity. How does that ring adjuster work? How does the screw that Alberto mentioned work? What do the switch contacts look like after years of use, switching a ~9 amp current?

#9: Post by **algue** » October 25th, 2013, 1:46 pm

I guess that ring could be a macro setting while screw is a finer one.
This could explain why ring is glued in factory.
The problem with the screw is that is made of very soft material. It is necessary to use a plastic screwdriver.

October 25th, 2013, 2:20 pm

I turned the screw with a metal screwdriver that fit it well. That worked fine. That screw seems to adjust the tension of the rocker on the microswitch. I may fish it out of the garbage and take it apart, but I also like Allon's idea. If not with this part I may apply it to others in the future. Stefano wrote to me that maybe the deadband of the Mater PSTAT is too wide, but since I'm monitoring temperature at the group I think it'll be okay. Will be dialing in the machine with the replacement PSTAT this weekend. It worked well enough yesterday morning but was a bit cool.