(My first post -- please be gentle!)

I just started my first foray into prosumer / commercial espresso machines, by picking up a lightly used Rancilio S27 for a great price. It has been working great, and is still in light use at my home -- probably 50 shots in the last 3 weeks. Once I got the grind dialed in and worked on my technique (still a work in progress), my shots have been getting better and better. I have the machine pulling from a 5-gallon water bottle, which hadn't posed any problems at the outset.

But starting a few days ago, I have been getting steam and/or air from the group. When running a cooling flush, the "water dance" just keeps going and going. I can see bubbling at the grouphead. Pulling shots, basically the same thing -- the filter looks like it's blowing bubbles through the espresso. (I use a bottomless portafilter.) The volumetric pump yields highly variable quantities of liquid -- (estimating) from 0.5oz to 2oz for a doppio.

I don't think the pump is sucking air at all -- its sound has been a very consistent, soft 60Hz buzz. Exactly the same since the day I got it. The only air in the supply line would be a small amount when changing the water bottle -- that shouldn't typically be a problem, right? Once I get into a situation where I can plumb this thing in, that's the first thing I'm going to be doing!

The S27 comes to pressure just fine (1.1 bar after an hour or so), and steam and hot water work great. Am I correct in thinking that this means that the overpressure valve is fine, since the boiler comes to pressure?

The only other thing I can think of is that I started noticing boiling sounds ("steamy", like a kettle of water just before it's at a boil) while the machine was coming to pressure. I think these started right around when my problems started, and I had never heard them before.

I'm not extremely mechanically inclined -- I can read a schematic and generally understand electrical work, but if it comes to anything mechanically complicated I might be looking for espresso repair shops in Chicago that do house calls! I don't know the S27's internals right now, and I'm not terribly familiar with HX internals in general, but I'm willing to learn.

Thanks for any suggestions!

Crack in the water jug hose or problem with fittings

I'd have to agree, that seems like a most likely culprit. I've never heard a rotary pump sucking on a mix of air and water, so it may well sound pretty normal. Easy way to tell is to draw water from the group when it's cold and you know there's no boiling of any kind. If you get lots sputtering then, you know it's from air in the line. Very strange, but I bet air would explain the erratic behavior of your flow meter as well: it relies on a jet of water to spin a little propeller whose rotations it counts. I'm guessing shooting intermittent jets of pressurized air probably makes it a little wonky.

The fact that the boiler comes to 1.1 bar and holds that when pulling shots is good, that means you don't have any leaks between the HX and boiler. However, that has nothing to do with an overpressure valve. It's set by the pressurestat. The overpressure valve is on the brew line and should open around 11-13 bars, to relieve pressure from thermal expansion in the HX as it idles and super-heats the water. You'd need a brew pressure gauge to make sure that's operating properly; I have no idea if the S27 sports one of those.

As for water boiling noises, am I right to assume that what you're hearing is the bubbling sound, and not a hiss? If so (if it's a bubbling), it's typical to hear that noise when the heating element activates, particularly right before it starts pressurizing the boiler and then periodically as the element activates on a cycle while on. It should be fairly quiet but noticeable. It varies from machine to machine AFAIK, probably has to do with the wattage of the element and the degree of resonance you get inside the body of the machine. Hissing is usually indicative of a leak in the steam boiler, often from the vacuum breaker valve, which would likely need to be cleaned or replaced. It could also be air coming out of the overpressure valve, though, if that is your problem. Probably depends where the OPV is mounted on the machine if that's even possible.

Let us know how it goes. Good luck.

Thanks everyone for the helpful replies. I disassembled the machine the other day, found a parts manual, and started becoming familiar with it. It was a great learning experience. I think the consensus is correct that this might be a leak in the intake hose -- it got better when I topped off my 5-gal bottle, so I guess replacing that intake line would be a good place to start! Further rambling and discussion below, because I just can't leave well enough alone.

shadowfax wrote:I've never heard a rotary pump sucking on a mix of air and water, so it may well sound pretty normal. Easy way to tell is to draw water from the group when it's cold and you know there's no boiling of any kind. If you get lots sputtering then, you know it's from air in the line. Very strange, but I bet air would explain the erratic behavior of your flow meter as well: it relies on a jet of water to spin a little propeller whose rotations it counts. I'm guessing shooting intermittent jets of pressurized air probably makes it a little wonky.

Good point on the rotary pump not necessarily sounding weird -- I was listening for angry cavitation noises but I suppose not hearing noises I've never heard doesn't really tell me anything.

I did notice sputtering (though less violent) when drawing water through the group on a cold machine. So that in my mind at least indicates that this problem isn't caused by a crack in the HX.

shadowfax wrote:The fact that the boiler comes to 1.1 bar and holds that when pulling shots is good, that means you don't have any leaks between the HX and boiler. However, that has nothing to do with an overpressure valve. It's set by the pressurestat. The overpressure valve is on the brew line and should open around 11-13 bars, to relieve pressure from thermal expansion in the HX as it idles and super-heats the water. You'd need a brew pressure gauge to make sure that's operating properly; I have no idea if the S27 sports one of those.

Good point. When I opened up the machine and looked around I realized I had confused the OPV (in the brew line of course) with the boiler safety valve and the release from the three-way group solenoid. All three dump into the drip pan, all three completely different things! At least I'm learning.

One possibility I considered is that there could be a leak in the OPV that was letting air into the line; however, I'd expect to be seeing some other symptom of that, like water from the brew line leaking from the valve, right?

shadowfax wrote:As for water boiling noises, am I right to assume that what you're hearing is the bubbling sound, and not a hiss?

Yeah, I wouldn't take that noise as diagnostic of anything. It just sounds like water boiling. 90% chance is that it is exactly the same as the day it was new and I'm being an espresso hypochondriac.

Thanks so much shadowfax and Heckie for your suggestions. Though this is about the simplest of problems I could have, I'm learning a lot by reasoning through it.

You bet Brad, glad to hear your excitement about diagnosing the problem. Please keep us updated with the results of your diagnosis.

Enthusiasm can produce a lot. While I "hear you" that everything was fine & dandy for a couple of weeks, rotary pumps can get in a bad mood quickly when asked to "suck from a bucket". The water being pumped is also used as a lubricant between the pump's vanes and their housing.

I DO NOT make a habit of working on espresso machines but a friend brought his Astra over for some "work". The only reasonably available outlet was in the garage so I rigged up this setup. It gave the pump a small positive head on the suction side and worked well. I am NOT suggesting this as a permanent change for you but it might help in troubleshooting.



It would be nice if your tubing going to the 5 gallon jug was, say, 3/8" OD. Another test you can make is to measure the water flow (machine cold) out of the grouphead. 500 ml/minute would be nice.

erics wrote:I DO NOT make a habit of working on espresso machines but a friend brought his Astra over for some "work". The only reasonably available outlet was in the garage so I rigged up this setup. It gave the pump a small positive head on the suction side and worked well. I am NOT suggesting this as a permanent change for you but it might help in troubleshooting.

I've seen bottom-feed setups like the one you posted. It's been a long time since my physics courses, but I'm not convinced that that changes the pressure available to the pump. My situation is basically like yours, with the intake on the bottom of the machine and the bottle next to it, except that my hose runs up and through the top of the bottle. The end of the hose is at the bottom of the bottle, approximately the same elevation as the intake. Once the hose is filled with water, it seems like the intake pressure would be equivalent to the situation in your picture with a horizontal hose. The extra force needed to draw the water to the top of the bottle is countered by the weight of the column of water coming back down outside the bottle.

What would give a boost is to change the pressure at the bottom of the bottle, for example by elevating the bottle relative to the intake. But I don't think the position of the hose matters. (This is just my intuition -- I may be dead wrong! I'm a programmer, not a mechanical engineer.)

I am certainly planning on plumbing this in as soon as is practical, though. Made an offer on a house today... if that goes through, I have my sights on an espresso mini-bar in the basement

erics wrote:It would be nice if your tubing going to the 5 gallon jug was, say, 3/8" OD. Another test you can make is to measure the water flow (machine cold) out of the grouphead. 500 ml/minute would be nice.

The intake hose is standard 3/8" braided stainless (dishwasher hose).

I did replace the intake hose this evening, and things seem much better at the grouphead. It runs only 300 mL/min cold, but the air from the shower screen seems to be gone (cross fingers). Tomorrow morning's shots will be the true test.

Thank you very much for the suggestions. It seems like you are very well experienced and I appreciate your advice.

You are correct as regards the water levels - I was thinking you may have been drawing from a jug resting on the floor with several feet of height differential. A new pump can typically take a six foot differential assuming some minimal friction losses in the inlet pipe but you (and I) were well within those boundaries.

300 ml/min doesn't bring any smiles but it is good to hear that the grouphead flow is more uniform than previously. I suspect that you are pretty low on brew pressure but when you finally get plumbed in, feeding the pump with 25-35 psi water, that flow will approach 500 ml/min.