I'm grateful for the previous help that I had with some gushing; I've taken to the Staub technique and it works very well. I also replaced the burrs in my Rocky.

But now I have another problem with my Expobar Lever. During a shot pull (not everytime, which is frustrating to pin down), I will suddenly see the water flow restrict markedly. I thought at first this was just the natural expansion pressure within the portafilter of the grounds, but it is really too much restriction and is resulting in much less crema now. If I see this phenomenon happen, after the timing is complete for the shot, I continue by removing the portafilter and trying to run some more water--I get some steam and a much lessened water stream.

But by the time I've knocked out the grounds from the portafilter, often I can get normal water flow again! Almost always I can get normal flow again after two to three minutes of pause. This inconsistency is driving me nuts as I can also pull a couple of shots and not have a problem at all!

I've replaced the pump once, over a year ago. I've just replaced the hi-limit switch. As I say, I've replaced the burrs in the Rocky (quite a difference I'd say!). But now I'm stumped with this slowing water flow.

Does anyone have thoughts about this pattern?

Much thanks,
Craig

It could be the pump or scale buildup among other things. When was the last time you descaled the machine and took the group apart for cleaning?

CTurner wrote:But now I have another problem with my Expobar Lever. During a shot pull (not everytime, which is frustrating to pin down), I will suddenly see the water flow restrict markedly. . . . But by the time I've knocked out the grounds from the portafilter, often I can get normal water flow again! Almost always I can get normal flow again after two to three minutes of pause.

I have never met an Expobar, but I once had a machine with a vibe pump which exhibited exactly these symptoms when the pressurestat turned the boiler heating element on during a shot. When the heating element turned off, the pump again had full power and would work correctly.

Thanks guys.

I'm going to keep your suggestions. Right now, I'm working with WLL and they have suggested that it may be the OPV. I might need a new one according to them.

Best,
Craig

It's quite possible.

It's also possible that it's the heating element kicking on. You can check one of these two options very easily.

If the light kicks on when the flow rate starts to decline, you know it's the heating element.

If the decline occurs regardless of the heating element, you can bet it's the OPV, or scaled water lines.

Of course, it's possible that the pump is giving out. It's hard to tell without a manometer.

Thanks for those tips. I'm waiting on the OPV and will report back with the result.

At the moment, I can't even use the machine because during an extraction, the flow slows down and stops completely. If I remove the portafilter there is a lot of steam but almost no water, and there is a low hum from the machine.

Craig

I got the OPV from WLL yesterday and spent a couple of hours in the evening putting it in. It was easier than I thought it would be. The old OPV had some adapters that actually made it look different from the new one, but once I saw this it was not difficult to switch off to the new.

I ran the machine for a bit in the evening and the water flow was okay.

This morning, I pulled a decent shot after my usual 40-minute machine warmup. I left the machine on until this afternoon when I tried to pull another shot. I got the same slow down to trickle water flow. I tried to time a complete shot, removed the portafilter and moved the on lever---steam but almost no water.

I waited for about 10 minutes and the water flow seemed to be back again.

I'm stuck until Monday when I can call WLL again.

Craig

Hi Craig -

Take the plastic line from the new OPV valve that goes back to the tank and stick it in a pyrex measuring cup - you may need to weight it down a little to keep it in place.

With the machine fully warmed up, flush as usual and then "pull a 25 second shot" using the blind basket. The OPV line should be flowing pretty steadily during those 25 seconds and, at the end, you should have a litle over 3.5 oz in the pyrex cup.

Now prepare a real basket and follow your normal procedure for pulling a shot with the OPV line in the emptied measuring cup. If all is well, you should get about 2 ounces in the cup in 25 seconds and about 1.5 ounces in the pyrex cup.

Any change in the sound from the pump when the flow diminishes? How long have you had this machine?

Eric,

Well, using the blind basket, the 25 second flow was between 10 and 11 oz.!

I was so startled that I basically stopped there and wanted to check back with you for your reaction.

I've had the machine about three years.

I've been flushing water all evening. I drew a good 22 second extraction to make an ice espresso drink for my son!

Thanks,
Craig

YAWSA !

That flow from the OPV return line to the tank is "as if" the OPV is stuck in the full open position or very close to it. A test for this would be to see if there is any flow in the OPV line when you simply flush with no PF in place at all or just an empty PF.

The Expobar likely also has a "priming valve" attached to the pump before the OPV. The discharge from this valve is typically tee'ed into the OPV return line on Quickmill machines whereas the Expobar hydraulics (Brewtus) show it as a separate line back to the tank. If this valve is stuck open or IS AN INTERMITENT STICKER, it would give the results you are experiencing.



edit - the more I think about it, I believe this self-priming valve is the source of the problem