Why does water continuously run through the brewing head?

Well, @kyle is in the ballpark, now it’s time to order some popcorn and crackerjacks.

@m.d.decker, your pump is running constantly.

A pump that is always on, or never on, depending on the machine, is usually a failed water level probe, reed switch, or sensor. When a probe, sensor or switch fails, it can be in open or closed state or it can just not be able to detect the correct condition, such as water level in the boiler in preparation for a next cup.

This could also be interference with a probe/switch/sensor, a defective or ineffective (due to mineral build up or running it without water or ignoring a “descale” indicator message for example) water level probe is the more likely point needing inspection.

As well, as another way of looking at this, Keurigs (such as the BKC600/700XL models) follow an algorithm of filling the boiler somewhat in preparation the next cup. It does this by:

1. Applying a 12 V signal to the aft pneumatic solenoid valve causing it to open;
2. Next, a 12 V signal is applied to the water pump activating the pump;
3. The pump driven water pressure opens a spring loaded check valve, allowing the activated water pump to force water in through the bottom of the boiler;
4. Air from boiler is displaced through a hose at the boilers top and through the aft pneumatic solenoid valve exhaust out the overflow tube at the back top right of the water reservoir into the reservoir air space.
5. This allows the water level to rise to the height of the water level probe corresponding to the smallest cup setting, upon which level being reached will cause the water pump to be turned off by stopping the 12 V signal application to the water pump.

After all this, if the water level probe has done its job and shut off the water pump, a process will begin whereupon other valves are opened by application of a 12 V signal and only then will the boiler be activated to push the temperature up the PID controlled temperature as designated in the digital menu on the machine. Once that temperature is reached the BKC600/700XL models will indicate on the screen that it is ready to brew. If you don’t get the hot water, the algorithm/process never reached the point where the boiler was activated, a state dependent on the water level probe detecting the water level correctly and first turning off the water pump . . . something that apparently is not happening if water flow from your machine is trying to force you to build an Ark.

So there’s your most likely problem then . . . a faulty water level probe. This could be caused by a bunch of things, but scale/mineral buildup is the likely culprit. You are going to have to take advantage of your on off switches/plugins and careful timing. Try this:

1. While unplugged, empty the water reservoir completely;
2. Fill the empty water reservoir to the “Max” line with Vinegar (takes about 1.8 liters or 60ounces/half-a-gallon), and put in place in the machine;
3. Get a bunch of cup or three big cups;
4. Plug in your machine and get ready to catch some water and vinegar!
5. When the water reservoir looks like it is getting close to the bottom of the barrel, unplug that sucker big time!
6. Let the machine sit with the vinegar in the boiler for at least 4 hours (it’s too bad it won’t have heat during the four hours but this is just to try to address a mineral build up on the water level probe that is stopping it from doing its thing);
7. After four hours, dump out the reservoir’s remaining vinegar and give ‘er a good rinse and then fill it up to the “Max” line with water again (you should always be using filtered water to keep the mineral-build-up beasts out);
8. After putting the water reservoir in place, get your big cups or containers;
9. Plug the machine in again and if it starts just running again, let it clear the vinegar out and let the water run into the boiler to cleanse it out by again running the water down to the bottom of the reservoir;
10. Repeat and rinse if the problem persists once more and if that doesn’t free up the water level probe to do its sensing again, the failure of the problem may be more complicated.

Good luck! Report back for all to see for future fixes if it works.