My five year old, Rocket Espresso Giotto Professional has recently started to behave unusually.

Here's the symptoms. Occasionally, say every few days, the Giotto's pressure surpasses normal ranges (1.0 bar) and continues climbing until the pressure relief valve fires. On these occasions, the Giotto will continue building pressure beyond 1.0 bar up to 1.5 bars for several cycles and then, generally, returns to normal operation. This morning, however, the Giotto failed to self-correct. The pressure relief valve fired, again and again, but the machine didn't return to normal operation. I had to turn the Giotto off, release pressure via the steam wand and let it rest. When I turned the Giotto back on a half hour or so later, it returned to normal operation.

I would surmise that the p-stat is dying, although I am confused by the self-healing and selected error rate. Can anyone advise? If the p-stat is the culprit, can I merely swap out a new one?

This, of course, assumes that the p-stat is the cause. Are there other possible causes?

Remove the cover from your pstat and post a pic. You may be able to simply move the wires from one set of terminals to another . . . MAYBE.

If you have a Sirai pressurestat and the problem is caused by a burnt set of points, moving the wire to the spare point set would do it. However, if the problem is caused by the diaphragm getting stiff and sticking that wont do anything. You can get a rebuild kit which will replace the diaphragm but the last time I checked, the rebuild kits were not much less than a Sirai replacement.

It took a month to get around to changing the p-stat. Very easy replacement that seems to remedied the problem.

For those following this post in future, I purchased the replacement Sirai p-stat from ChrisCoffee, which cost about $100. It is a bit larger and much more robustly constructed than the original. The replacement unit has three tab (positive) connectors versus the two (positive) tab connectors of the original, and is crafted of metal versus plastic. It required a 90 degree rotation to fit, but beyond that replacement was quite straightforward.

I'd advise in a week or so, should there be any issues. I will also advise if I need to follow other remedies. The other possible cause (suggested by Seattle Coffee's) would be a calcified pressure probe.

Thanks all,

Tom