What are symptoms of the B II pump starting to fail?

[Richard]

I have a Brewtus II that is about 12 years old.

I recently replaced the pressure stat and the  o-ring in the vacuum relief valve..

I am now seeing the brew pressure fluctuating when pulling a shot.

Pressure gradually goes up to 9 bar, pauses, drops to 6 bar and then back up to 9 bar. Sometimes this happens several times while pulling a shot.

Is this a signal that the pump is starting to fail?

What are other symptoms of impending pump failure?

Another fact: I can't turn the screw that adjusts the pump pressure. It is frozen.

It may be possible that I have a loose electrical connection inside that happened when I replaced the pressure stat.

I plan to open the Brewtus and check all the connections.

[jt123]

I had something very similar, and if you read further back you'll see comments suggesting its related to either the OPV or the pump, or both. But it is not definitive which is exactly at fault.

Personally I did the WLL's drain tube measurement to verify pump performance, and found that not enough water was being ejected when you use a blind basket. In my case, the OPV was set to high (around 12-13 bar). When it is set this high it seems to affect other function. When I dialed back the OPV the drain volume was correct again. Another thing I had was a tiny kink in the T of the drain tube from the OPV assembly, so not sure if that was related... the way it was installed there is still not a perfect line running from there, but so far the machine has been operated normally.

The strange thing I observed, and I expect you *may* see as well, is that when you use the blind basket the pump WILL hold full pressure without periodically switching back to 6 bar. It is only during actual extraction that this oscillating behaviour occurs. Is this your case?

The other interesting, but possible coincidence was that this jumping back and forth between 9 and 6 bar while brewing was perfectly in sync with the PID controller's activations, Basically when the element was on, it would go down to 6 bar, and when it was switched off, the pump went back to 9. I have a B III with the PID, and the dot/decimal point blinks when, as far as I can tell, the brew element is being activated. But I don't know how this would translate to a non-PID machine, since I expect a thermostat would have a considerable deadband and not exhibit this kind of pulsing power cycling for the element.

[Richard]

JT,

Thanks. Very useful.

You are right, when I use a blind basket brew pressure goes to 10 and stays there.

It oscillates only when pulling a shot. Never with the blind basket.

I will open the machine soon and check your suggestions about the kinked drain tube.

I am also going to check the wires going into the PID. I had a problem with them a few months ago and thought I had fixed it. 2 wires dropped out of the connection.

The way the wires tighten into the PID is a little strange. There is a bar in each slot that goes up & down when you turn the screws. The wire goes above the bar. Turn the screws clockwise and the bar goes up and pinches the wired against the PID contacts.

How did you resolve your oscillation problem? Was it the pinched tube?

Did you replace the pump & OPV?

I was thinking of ordering that from WLL to make sure I have one nearby if the pump dies.

[jt123]

In the end, I'm not sure what it was since I un-kinked the tube AND changed the OPV to 10 bar from 12-13 in one go. My guess it was the latter OPV adjustment that fixed it. Wasn't scientific enough to adjust it back to see if I could reproduce the error condition... :P

Didn't get any new parts, although I feel like having the pump/OPV assembly on hand at this point would not be too cautious... The pump was replaced a few years ago according to the previous owner, but the job wasn't done great from what I can see: new OPV doesn't quite line up due to some slightly sloppy pump mounting work, and the inlet tube didn't reach far enough into the tank so the pump would run dry when the take is only 2/3 full. This would lead to more dry pump situations which can't be good for the life...

Overall, what you're experiencing doesn't sound like an electrical problem. However, at least in my case the perfectly timed pressure drops with the PID activation made me a bit suspicious... you can see this with the dot/decimal place under the temp display of the PID - when you see the dot it means the brew element is on - I've verified this with a power consumption meter after the machine is steady with the steam light off - each blink is associated with a spike in the power draw which has to be the PID turning on the SSR to power the brew element. This timing was bit too uncanny to ignore. It's almost like the pump is working at some electrical/mechanical limit, and when the brew element gets power switched on there's a slight drop or interference in the power supplied to the pump which results in the drop in pressure. Another theory that could support this is holding static pressure (with blind) is not quite as intensive as when there is flow (i.e. when brewing), so this is why it can hold at higher pressures but can't fully supply the 9 bars of brewing pressure when there is flow. But now this is a pretty hand wavy explanation. Anyway... this is really stretching my knowledge as an electrical/computer engineer who works with much lower power stuff and software most of the time, so take it for what its worth... :P

[Eric Christoffersen]

I had oscillating brew pressure problem, turned out to be the ancient cooked seals in the group head:

https://groups.google.com/d/topic/brewtus/6d7wrpEcxk8/discussion

[Richard]

jt,

I think you had the same symptoms I see, but a different cause.

I opened the Brewtus. No visible kinks in tubes coming out of OPV. Just to be sure, I rerouted those tubes so they were clear of wires. 

My brew pressure with a blank portafilter in is 9.8. I can't adjust it. The screw in the OPV is frozen.

I checked all electrical connections.

I brewed a shot and the pressure oscillated.

I then went and did the flow test in the video you sent.

With a blank portafilter, the flow starts and then stops. Just like in video.

But, the flow does not start up again. Different than video.

I suspect that either the tube is clogged and I can't see it. Or, the pump is starting to fail.

I did order a new pump assembly a few days ago on general principals.

When I receive it, I will call WLL and check the symptoms with them.

[Richard]

Strange Repair.

I was about to replace the pump.

I remember several people who replied that similar symptoms happen if the intake water tube was pinched and water flow to pump was restricted.

I had checked that and did not see a problem.

I decided to replace the tube before I replaced the pump.

Step 1 as a check, I disconnected the input water filter and pulled a shot.

Same problem.

I reconnected the water filter and pulled another shot.

Problem FIXED!!!!

Very strange. I pulled 2 more shots and it still worked normally. Start shot, brew pressure goes to 9.5 bar and stays there.

Does anyone know why this would work?

My only idea was that there was an air bubble that got fulshed out.

[Richard]

The repair was temporary. After a few shots, the fluctuating brew pressure problem returned.

 

The clue is that the problem was related to a restriction in input line.

I finally called WLL and they said that the fact that it went up to 9 bar steady with blind portafilter suggested that pump was OK and the problem might be in a restricted input.

They were still out of stock in the required tubing that should have been included with the new pump kit that I had received. 

I ordered 4mm x 6 mm silicone tubing from Amazon.

$5 for 10 feet.

I replaced the input tubing to the pump.

PROBLEM SOLVED.

I tested by pulling 4 shots over 2 days. the brew pressure is now steady.

Bonus: the Brewtus is now quiet all the time when not pulling shots.

Another symptom of the restricted water input line was that the Brewtus pump had been cycling on for a few seconds a few times an hour.

It is quiet now.

[jt123]

good to hear you solved it! It's been a few days since - do you think the fix has been permanent at least up to this point?