Disassembly Adventures with the DeLonghi EC155

Jim Avera (jim.avera at gmail dot com). Updated 9 Sept. 2015, 31 May 2020

So your DeLonghi EC155 won't pump water any more, or not enough to make decent espresso. Or maybe it makes a horrible racket and vibrates so much your cup slides out of the stream, or even entirely off the platform. Let me tell you how I fixed these problems.

If you search on-line, stopped-up water flow and noise/vibration are frequent complaints about this otherwise-great, and inexpensive machine. When it works, the EC155 makes high-quality espresso, but it is not a maintenance-free appliance.

Coffee Crud

Fine coffee particles and who-knows-what-else will accumulate everywhere you aren't looking, such as under the Diffuser Screen at the bottom of the boiler, under the portafilter screens, and in the pressurization valve (disassembly details below).

Note: I eventually figured out that a too fine grind causes frequent stoppages, especially in the porta-filter pressure valves. Adjusting my grinder to a slightly coarser setting improved reliability a lot.

Scale Buildup

Most water, even if filtered, contains dissolved minerals. When boiled, pure H2O escapes as steam, but the minerals which were dissolved in that water stay behind in the boiler. Eventually the minerals become too concentrated and precipitate as solid particles.

You can avoid mineral build-up by using distilled or de-ionized water, but that might not produce the best coffee. Some minerals make water taste good (that's why distilled water tastes “flat” and uninteresting). And some (e.g. magnesium) are necessary to extract the best flavors from coffee beans.

To get the scale out, you have to mechanically clean the clogged parts and/or dissolve the mineral particles using a (dilute) acid solution. The EC155 manual recommends using Citric Acid or a “commercially available product”. I used white vinegar with decent success. YMMV. The easiest method is to “Clean In Place” by simply running the acid solution through the machine, letting some soak overnight. This works for minor build-up, but sooner or later you have to take some stuff apart.

Cleaning The Portafilters

Dismantle each portafilter cup by unscrewing the plastic “nose” which sticks out the bottom, and then push out the metal screen, rubber gasket, and interior plastic part. Clean the parts and soak overnight in your de-scaler solution. Push or pull the plastic pressure valve open a few times in case it is stuck closed. When re-assembling, be sure the plastic pin goes through the small hole in the metal cup.

Cleaning Diffuser and Check-Valve

You will need short-handled screw-drivers, both Phillips and regular flat-blade.

Unplug the unit and let it cool if necessary. Open the steam valve to discharge any pressure.

Remove the Diffuser Screen from the bottom of the boiler with your short Phillips screw-driver. You can place the unit on its side, on a towel to catch drips (remove the water reservoir first!).

Then use the flat-blade screw driver to remove the brass part in the center, where the water comes out. Behind it is a small spring with a clear plastic bulb on the far end – this is part of a check valve. Clean all the parts carefully, being careful to not damage the surface of the plastic bulb. There is a valve seat deep in the tube but you probably can't remove it. Use a Q-tip to probe the valve seat for gunk, but be very careful to not let cotton fibers or anything else get inside the boiler (see below if you think you need to take the boiler completely apart).

Cleaning these parts, and the Portafilters, is probably all you will ever need to do. Running a de-scaling (acid) solution through the machine, and letting some sit hot for a while and then overnight, should remove most scale build-up inside the boiler.

Reducing Noise and Vibration

Really, this makes a big difference! We're going to slightly re-position the pump and a connecting hose so they don't rest against the outer case. To do that we have to remove the top of the case.

First un-plug the unit, remove the reservoir, and open the steam valve to discharge any pressure.

Remove Case Top

Turn the unit upside-down and remove two long, narrow black screws from the front corners of the upper case. Then open the reservoir lid and remove two more such screws from the rear corners of the upper case. Remove the steam-valve knob by pulling straight up (a little prying with a flat screw driver may help). Then take off the top, exposing the innards.

Positioning the Water Supply Tube

There is a skinny (about 1/8” diameter) hard plastic tube which runs from the pump assembly to the boiler. It vibrates somewhat violently while the pump is running, and if it contacts the side of the case the noise is greatly magnified. On my unit, the tube was quite long and coiled around the pump assembly before heading to the boiler. By coiling it in the other direction, the tube was positioned away from the exterior case, so it stayed in free air while vibrating.

To re-position the stiff tube, you have to first disconnect one end. Remove the spring clip from a slot in the brass coupling attached to the boiler. Use long-nose pliers; the clip slips out easily. With the clip removed, the tube can be pulled straight out. Now you can re-position the tube (but be careful to not kink it). In my case, I wrapped it around the pump assembly in the opposite direction from where it was before. When you're happy with the set-up push the end of the tube all the way into the brass fitting, and re-insert the metal clip into the slot – it should slide in easily.

Pump Positioning

The pump hangs from the metal chassis, with rubber shock-absorbing bumpers on all sides. The pump and the cavity it lives in are both roughly rectangular, but the pump can be mis-aligned. Twist the pump assembly slightly to equalize the spaces around the pump and prevent any “hard contact” with the case. The power cord and water tubes should hang freely without being pinched (if they are, see disassembly instructions below).

That's it. Most people will never need to do anything more inside the case.

Re-attach the cover, using two long black screws on the underside and two on the top, just inside the reservoir lid. Press the steam-valve back onto the stem.

“I'm Going in!” – Boiler Disassembly

Just to reiterate, most people can fix their machine by simply cleaning the portafilter (or just wiggling the pressure valve), and removing and cleaning the Diffuser Screen from the bottom of the boiler. The next step would be to take out the plug and check-valve from the bottom of the boiler without opening the case, and running de-scaler (acid) solution through the machine and letting it soak overnight. Noise and Vibration can be reduced by the limited internal work described previously.

But if, for whatever reason, you need or want to take your EC155 all the way down to its bones, here is some guidance.

You will need a 5 mm Allen wrench, Torx T-20 “Tamper Proof” star driver, and a smaller-than-usual Phillips screw-driver. Harbor Freight Tools Item #97471 (tamper-proof star key set, $6) has the necessary Torx tool. They also carry a cheap screw-driver set (Item #47770) which has what you'll need.

Remove Bottom Panel and Disconnect Hoses & Cord

Remove the four silver-covered Torx screws from the bottom and remove the bottom panel. Pull the two plastic hoses off of the reservoir nipples and detach them from the plastic bracket. Un-hook the AC cord strain-relief. Releasing these items will allow the chassis to be removed later.

Remove Chassis

Remove 4 silver-colored screws from the corners of the sheet-metal chassis around the boiler. Remove the front control knob (pulls straight out, after a little prying). This exposes two screws, which can be removed with a small Phillips screw-driver. Gently push the control shaft through the front panel, while wiggling the chassis backwards slightly, and free the control switch and the two indicator lights from the panel. Leave all wires connected, and be careful to not yank anything.

Finally, un-screw the plastic steamer nozzle and wiggle the metal wand around so that the clamp attaching the hose to the wand slips through the oblong hole in the chassis – leaving the clamp below the chassis. Then lift the chassis, with pump attached, up and out, meanwhile manipulating the steamer wand to pass through the opening in the case.

If you accidentally yank some wires loose, see the Wiring Schematic below. Otherwise the most likely result of yanking is to dislodge a thermostat. There are two, and they are held against the side of the boiler with springy metal clips. The thermostats can be recognized by the white thermal grease under them. Be certain that each thermostat's retaining clip lies in the recessed slot in the ceramic portion, where it can't touch any electrical terminals.

Opening the Boiler

Disconnect the skinny water inlet hose (#80 on the parts diagram) from the boiler as described in the “Vibration” section above.

Use a 5mm Allen (hex key) wrench to loosen the four black bolts a little at a time. The black bolts extend through the two halves of the boiler, a thick aluminum bottom-piece (which hold the portafilter), and finally through the sheet-metal chassis. On the bottom are silver-colored nuts with a knurled face.

Separate the stainless-steel boiler from the other parts. Remove the rubber portafilter gasket. Dislodge the bottom half of the boiler from the top by gently hammering with the plastic handle of a screw-driver. You want to avoid denting the metal or damaging the gasket which sits between the two halves.

Now you can see inside the boiler. There's nothing much there except for the heating element.

Boiler Re-Assembly

Be sure everything is clean, especially around the gasket between the halves of the boiler.

Carefully assemble the boiler, with gasket between. Put on the black rubber portafilter gasket, and then the cast aluminum bottom piece. Place the assembly in the sheet-metal chassis. Important: Align the water-inlet fitting towards the rear, where the skinny water hose wants it to be. Align the aluminum bottom casting so that the ground ⏚ connection tab (which is not used) faces the left side of the unit (the right side from your perspective while facing the front panel).

Insert the black Allen (hex key) bolts through the corners and attach the knurled silver nuts on the bottom of the chassis. The bolts should be quite tight.

Insert the skinny water hose all the way into the brass fitting on the boiler, and re-insert the spring clip.

Putting it All Back Together

Drop the power cord and two hoses down through the pump compartment. Place the chassis loosely in position with the pump part-way in (rotate the pump if necessary to align with its compartment).

Manipulate the steamer wand to get it through its hole; this is a bit tricky, as there is barely enough slack in the steam hose to move move the wand around to get it through – but there is enough. Finally, wiggle the wand to move the hose clamp up above the opening in the chassis; this will allow the chassis to slip down into place.

Install the front control switch and two indicator lights through the front panel. You can slightly tip the boiler back to let them slide into place. Install the two long silver-color screws through the front panel to secure the switch. Push the control knob onto its shaft.

Install the four silver-colored screws which hold the metal chassis onto the plastic case.

Invert the unit and re-position the tubes and power cord, if necessary, so they are not kinked or wedged between the pump and case. Rotate the pump so it is equidistant from all sides, to minimize noise.

Re-attach the hoses to the fittings below the reservoir, and clip the hoses into the plastic retainers. It doesn't matter which tube goes to which fitting. Clip the power cord strain-relief into the case. Re-install the bottom panel using the four Torx “tamper proof” screws.

At this point, I'd run a live test for leaks...

Live Test With the Top Still Off

Insert the water reservoir, filled all the way up. Place a container under the boiler outlet. Temporarily use the streamer-valve knob to firmly close the steam valve (turn it clockwise). Plug the unit in.

The boiler normally always contains water, but now it's empty. To minimize the length of time the heater “dry fires”, turn the control immediately to the “pump” position and leave it there until water flows out of the boiler. Then turn the switch back to the “pre-heat” or “steam” (highest-heat) position and wait for the green light. Return the switch to the “pump” position and pump a good bit of water into your container. Check for leaks around the boiler and where the water-supply hose attaches.

Don't touch anything inside without unplugging from power first!

Final Assembly

Remove the reservoir. Let the unit cool.

Position the top cover and install two long black screws just inside the reservoir lid. Install two more screws from the underside of the top case, near the front corners. Re-install the steam-valve knob.

If you haven't already, run at least two reservoirs-full of water through the machine and portafilter to flush out residual de-scaler.

Now make a cup of espresso!

Wiring Schematic