Is this a bad rotary pump? (video)

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by jgrosjean »

I don't seem to be getting full pressure at the group head.

I'm assuming it's a pump problem, but trying to verify before I spend a long time to send it away and get it rebuilt.

- The pump shaft turns easily by hand
- When turning I don't feel any catches, it's smooth

The machine is on a Rancilio S27 that had been on storage 10 years, said to be working well previously. I've taken apart the entire machine and soaked boiler/pipes/group head in citric acid. I also took pump apart (not internals, but connecting values) and gave them all a soak in citric acid too. Right now it's getting water from a garden hose (though I'm getting similar behavior when using a plastic bucket reservoir as the water source).

Does this look like a broken pump? Or is there something else that I can try before sending it in for a rebuild?


#2: Post by jgrosjean »

One more update... when adjusting the valve that's on the outflow part of the pump:

1. If I loosen that screw so much that it comes out and the spring behind it comes out... then max pressure is 3 bar.
2. If I put spring and screw back in and screw in a very little... also max pressure is 3 bar.
3. If I screw in half way max is 4-5 ... same as when I screw it in all the way.

Just mentioning because it's not linear... changing that valve seems to make no difference after half way in.


#3: Post by EthanL »

Hi Jesse, looks you are quite handy, why not isolate the pump and hook the pressure gauge directly after it on the outlet, see if you can get a full 9-bar pressure? It's hard to tell which link went wrong, and might not be the pump itself. Good luck!

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#4: Post by stefano65 »

First I suggest removing a wire from the heating circuit (Heating Element which should be easy to get to or the safety thermostat or pressurestat one of the easier one to get to)
after you dispensed the second time the hot water (unless your boiler is completely overfilled or there are other filling issues) and then while brewing from the HeEx line I could hear the pump running,
remove the water level probe's wire and making sure that you are not grounding yourself to the machine,
is the pump engaging?
Stefano Cremonesi
Stefano's Espresso Care
Repairs & sales from Oregon.


#5: Post by Giampiero »

The bolt on the pump inlet side, should be the cap of the pressure valve, i remember Procon pump has this system, but i don't know really what is the "valve" on the outlet side, i thought it was a water filter.


#6: Post by Coffcarl »

I dont have any rotary pump experience, but if you are up to the challenge, I would consider this: ... -parts-kit

I think I would look for wear indicators first before making this decision. But also, if this is the series 2 pump, $83 for a new one does not seem unreasonable. That's not much more than a new vibe pump.

Also, you ought to be sure the opv valve that you adjusted is truly closing.

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Team HB

#7: Post by Jake_G »

The factory pressure adjustment from Procon should be beneath the acorn nut. Rancilio has an odd habit of installing their own bypass valve after the internal valve for unknown reasons. Remove the acorn nut and show us what lies behind. You may have a failed O-ring between the inlet and pressure sides of the pump that is keeping an otherwise healthy pump from generating pressure.


- Jake


#8: Post by jgrosjean »

Thanks for all the replies... it's going to take me a bit to try things but I'll report back when I do. Thanks again!


#9: Post by jgrosjean »


Short story is that I switched out the pump and the replacement seems to work great-I even made my first espresso!

Thanks for all the help... I've posted a long series of questions trying to get this machine to work (probably more when I next break it) and I've got very helpful responses each time. My goal was to learn about espresso machines and maybe get one working, success!


Longer story is that when I purchased this machine it also came with a backup parts machine. I thought the pump in the parts machine was supposed to be broken, but I switched it in anyway and everything works now.

I'm pretty sure that the machine that I've been trying to get working (and was working well they say when put into storage) must have frozen while in storage. The heat exchanger was burst, and now that I look at it more closely the pump seems to bulge out slightly on the bottom where the plate with the company name and info is. I notice that on the replacement pump there is no bulge, so I guess things must be slightly misaligned inside the problem pump. And that misalignment must be why it can't reach full pressure.


I did take off the side acorn nut on the problem pump, but it doesn't look adjustable to me... the threads seem welded (or very stuck) into the acorn nut. I think I read that it's set at factory and not meant to be changed... you are supposed to always use OPV on the output side of this this pump setup I guess. I'm including pictures of the opened acorn nut and also of the slight bulge on bottom of pump.