I walked into a leaking GB5 and noticed there was no steam pressure, but the brew boiler had what it was supposed to have. I turned the power off, took the lid off the top and noticed water leaking out the safety valve and the anti vacuum valve (on steam boiler) when I turned the power back on. I turned the machine back off and I disconnected the high level probe so I could make the pump turn on, turned the power to the machine on and water began to spit out of the safety valve vigorously until I turned the machine back off.

Is the safety valve bad? The water was not hot.

Water coming out of both the safety valve and vacuum breaker sounds like an overfilled boiler to me.

Thanks, bob. That makes sense because water was immediately coming out of the valve which means it is above the high level probe. BUT, why would the water stop filling at all then? Also, what makes the steam boiler turn its power off?

What causes it to overfill?

While I have no experience with your machine, the last time I saw this it was due to scale on the water level sensor probe.

I would drain the steam boiler and pull the water level probe to look for scale. Be extra cautious to not damage the seal. Enough scale on the probe will cause it to not signal the pump to turn off properly/at all. The scale can be scraped off once you soak it in a citric acid solution for a little while. Once free of scale, re-install and fire the machine back up.

Hope this helps.

Firstly, just to get terminology correct, there is a "working level" probe and a "safety" level probe. At least from the parts diagrams, these probes are IDENTICAL except that one (the safety probe) is inserted 10 mm further into the boiler.

I would remove the vacuum breaker and syphon water from the steam boiler until it is maybe 1/3 full, i.e. essentially what Merle suggests. Remove both probes and clean with fine emory paper and vinegar to nice shiny metal. Unless you're intimately familiar with these machines (and I am not), it is easy to get the probes and their wiring confused so marks and tags are in order here. If the parts diagrams are correct, the working level probe is centered and the safety probe is to the right of it.

I SUSPECT that the heating element will not come on until the safety probe is "satisfied" but why take a chance? . . . disconnect the heating element wires.

With the clean probes re-inserted as per the sketch below, and the vacuum breaker still removed, fire her up.



If water starts coming out of the hole where the vacuum breaker was removed, time for more discussion from a GB-5 expert.