Denying an IT man access to coffee or pizza is always dangerous. Waking up this morning to find my Delonghi EC710 refusing to dispense water into the coffee sump could have led to an explosive situation if I didn't get my caffeine fix.
I should have seen it coming as I live in a hard water area and never bother running a cleaning solution through the machine. Attempts today to descale with vinegar, bicarbonate of soda and descaling tablets didn't yield any results so it was obvious this was going to be another screwdriver job.
Here's how it works....
An initial short run of the pump draws water from the reservoir into the boiler where it is heated by an electrical heating coil. There are two outputs from the boiler, one from the top runs through a pipe to a steam valve. When the steamer handle is turned, the steam valve opens and steam is piped out through the steam tube for frothing milk. The second output from the boiler is on the underside and is stopped by the normally closed flow valve. When the water in the boiler reaches the right temperature, a sensor switches on the OK light. When the light is on, the user pushes the pump switch and more water is pumped from the reservoir. The pressure in the boiler increases because the pump is trying to push in more water and this forces the spring loaded boiler flow valve to open allowing hot water to run out. As the sump filled with ground coffee is fitted to the boiler output, the water is forced through the coffee and out of the sump where it pours into a waiting cup.
When enough coffee has been poured, the user switches off the pump. The boiler pressure falls and the spring on the flow valve pushes the valve shut again.
In my case this morning the steamer was working but no water was coming out of the flow valve on the underside. This indicates water was getting into the boiler and was being heated up normally so it must be the flow valve at fault - probably encrusted with limescale.
To repair I had to disassemble the coffee machine and the boiler. Instructions on how I did this are below but please bear in mind the following safety points if you intend to do the same....
- You'll be fishing around in a compartment that houses water and electricity in close proximity. Disconnect from the mains before starting and keep some towels handy as spillages will be unavoidable!
- When you open the boiler, water will flood out. It shouldn't touch any electronics if the unit is upright and the internal design means water should be contained and drain out of the machine.
- Make sure the boiler screws are tightened fully upon reassembly. The water will be under pressure when in use and incorrect assembly of the boiler will cause hot water or steam to vent onto the electronics or out of the machine casing at points where is shouldn't.
- Remove the reservoir before disassembly.
- There will be hot surfaces if the machine has been running. Allow to cool before starting.
- Review all steps and ensure you have all necessary tools before starting.
Steps 11, 19 and 20 may be enough on their own to remove a clog from the flow valve without having to fully disassemble the machine. It's certainly worth a try before getting up to your elbows into the guts of your Delonghi. That said, if you have chunks of limescale lurking in your boiler, the flow valve will probably clog up again sooner or later.
The first three steps aren't strictly necessary for disassembly however if you're using a long handle screwdriver then removing the base makes it easier to gain better access to some of the screws.
Step 1. Remove the screw on each base arm...
Step 2. ... then lift and remove the arms.
Step 3. Remove the two screws on the base of the unit. Unlike in this photo I would recommend you avoid resting the machine on its back unless you are sure it has been completely drained. The black plastic base can now be pulled away allowing easier access to some of the screws that will be removed later.
Step 4. Undo the two screws on the top rear.
Step 5. Remove the coffee tamper by pulling and twisting.
Step 6. Remove the three screws. These are anti tamper screws and are star shaped with a nipple in the middle. Although I had a suitable bit that would fit these screws, the shaft of my screwdriver was too large to fit into the access hole. I managed to force these screws out using a small flat blade screwdriver which I was able to jam into the screws in order to get enough purchase to turn them. If you can't find a suitable tool to get these things out then it's a bit of a show stopper at this point. Upon reassembly I replaced these screws with normal Philips self tappers to make any future disassembly easier.
Step 7. With these screws removed, the top may be lifted away. The hotplate on the top section is still connected by a couple of thin wires so lift it carefully.
Step 8. To help with shifting the top out of the way, disconnect the hot plate/boiler heater connection. This will allow you to push the top of the unit away giving you the room you need to get inside.
Step 9. Unscrew the electrical safety earth and move the earth wiring out of the way.
Step 10. Use some long nose pliers to pull out the circlip that holds the boiler inlet pipe in place. Pull out the pipe to disconnect it from the boiler once the circlip has been removed.
Step 11. Unscrew, remove and clean the diffuser.
Step 12. Remove the two screws (arrowed red). The black plastic underside casing can now be pulled away (plastic tabs need to be pushed aside where arrowed in green)....
Step 13. Pulling away the plastic underside once screws and tabs are removed.
Step 14. Loosen the four black Torx (star shaped) boiler screws (front two arrowed). Water in the boiler may leak out at this point so ensure the unit is upright and a towel is placed underneath.
Step 15. Remove the four nuts (three arrowed) from the underside of the boiler unit.
Step 16. Lift up the top of the boiler assembly along with the steam outlet and place to one side. The two halves of the boiler assembly are sealed with a rubber gasket which should remain attached to the upper housing. Make sure this is properly in place when reassembling.
Step 17. The lower boiler assembly can now be lifted out.
Step 18. Here's my problem! Look at all that 'orrible limescale. It's bad enough having it lurking at the bottom of the boiler but as water is supposed to run down the channel in the middle (where the flow valve lives), I'm guessing that's clogged with the stuff too.
Step 19. With that yukky stuff cleaned out, turn over the boiler underside and unscrew the dowel.
Step 20. With the dowel removed the spring loaded flow valve can be taken out. It can then be cleaned along with the channel it sits in.
With cleaning complete, reassembly is the reversal of disassembly. As stated before, ensure the Torx bolts that hold the boiler together are secured tightly and that the rubber gasket is fitted correctly.
Once back together, it may take the pump longer than normal to refill the boiler as it is completely empty (normally some water from the last use would sit in the boiler).
A couple of useful links for those interested:
Exploded views and spare parts lists of several coffee machines including the EC710
Delonghi UK official product website
Enough talk... I need coffee....