Why isn't it pumping out enough steam?

SOURCE: steam wand not working

The steam wand ejects steam in order to froth the milk. The steam wand should be cleaned after it is inserted into milk and at the end of each day. Do not allow the steam wands to soak in water overnight since some of the dirty water can be sucked into the boiling tank inside the machine this may cause the steam not to come out
Unplug the machine, take the case off, disconnect the switch wires and test it with a continuity meter. If you don't get any continuity, or if it is constantly closed and never open, the switch is bad.
this could have been prevented by regular maintenance and proper use. The usual suspect is a gummed up wand or brew line or user error. Here’s what to look for and how to avoid it.
First, notice what kind of wand you have. Most semi-automatic and porta-filter espresso units will have wands that resemble those on bottom or right, although the tips may be different. Some tips do not slide up and down to alter the aeration, as the one on the bottom does. If your wand is from an older (1990s) unit, it could have a more bulbous tip and a smaller hole in the tip. Some of the new wands give you a manual/automatic control.
Many of the new super automatics come with an automatic frothing unit, like this one from Jura-Capresso. The nice thing about the frothing wands on Jura-Capresso's new units is that they allow for even more control.
The "Dual Frother Plus" (top) works like the traditional frothing wand. The metal sleeve goes up for steam, down for foam.
The "Froth Xpress Plus" is a very handy device which can be used with the included sleek milk container or a distinct milk container, like a 1/2 gallon jug. The Froth Xpress has a tube (hard for using the included container, flexible for using a different container) that fits into the frothing tube behind the dial shown in the picture above. After selecting froth or steam, the milk is siphoned into a cup below the steam wand. We recommend steaming the milk first, then adding the espresso.

Whatever sort of wand you have, it is essential to keep it clear of solidified milk which can gum up the tip and even the wand shaft. Here are some symptoms of a clogged wand:

• Little or no steam comes out of the wand
  
• Hot water drips from the tip of the wand
  
• A squeal or whistle comes out of the wand when the steam function is selected
  
• A deep humming is heard when the steam function is selected*
  

*This is also a symptom of another more serious problem, particularly if you have a pump espresso machine; so if unclogging the wand does not solve it, you should contact a technician.
A good preventative measure against the clogging of a steam wand is regular rinsing in warm, soapy water of the tip and any other removable frothing part. This should be done after each steam wand use. If your machine has a Froth Xpress, it is important to clean all of the hoses, valve, and connectors (be very careful with the plug, however, because it is delicate). All wands should also have steam jetted through them after a frothing cycle is run.
Another preventative measure is to run a steam cycle for about twenty seconds before each new use. This will eject stray particles before they can build up and cause serious damage. There is also a cappuccino cleaner available which can be used in the automatic frothing devices. The solution is placed in a reservoir, and a full cycle is run until the reservoir is emptied. This can be done every few weeks or every few months, depending upon use.
Aside from prevention, there are treatments for a clogged wand. First, remove the tip, if the tip is removable. Usually they are, as in the case of the plastic tips above. The holes are usually big enough to run a pin or even a small paperclip through (emphasize small) to remove the gunk. If these items are too large, do not attempt to use them; instead try using a thin gauge wire from an electrical wire strand. Next, the metal wand itself can have a pipe cleaner run up into it. Start out by putting just about a half inch of the pipe cleaner up the wand, rubbing it around, then pulling it out. Gradually work more of the pipe cleaner up the wand, but never let the length of pipe cleaner in the wand exceed the wand length. We recommend the pipe cleaners with the stiff barbs attached, as opposed to the mostly soft ones. Do the same for all of the hard hoses and connectors. With respect to rubber or soft plastic parts, rinse them in soapy hot water. If flexible hoses form holes, replacements are available (give us a call) or we've even had some luck at aquarium supply stores.
PLEASE NOTE: if you own the Jura X7 or the Froth Xpress Plus, the diameter of the tiny holes is very important. We recommend trying not to put pins into these holes. However, if they must be cleaned and soaking won't work, a smaller gauge wire, a single strand, should do the trick. Always use a strand that is smaller than the diameter of the hole.
Frothing wand technology is advancing at a breakneck speed, but along with these advances come serious precautionary measures for dealing with these very delicate mechanisms. Follow the steps above, and your machine should be producing full-fledged froth for its entire life.

SOURCE: my delonghi magnifica is having a problem with

There are 'o' rings on the pipes (on machine - not milk container) where the milk container fits into. replace or clean them - should work like new.

SOURCE: DeLonghi EAM3400 Magnifica with broken steam spout

No offense to Irishwarrior but the answer to your question is yes, you can buy a replacement. Call Delonghi. The inner sleeve has a flat spot on the back that matches up with the steam wand. No glue, and o ring holds it in place, either the o ring is worn out or the hole in the bottom of the sleeve is partially clogged creating more pressure than the resistance of the o ring. A paper clip straightened out will "****" it out. If you need to replace the whole steam wand arm you would want to order a new "tap" valve. Delonghi can give you the # of an authorized service center where you can order one (Delonghi will not sell you "internal" parts)

SOURCE: My Delonghi Magnifica 3400 has a problme with the

If the diffusor isn't suffering from built-up coffee grinds (in which case give it a good cleaning first), then check the backplane that holds the diffusor: it has two hex head screws that have probably come loose. Remove the diffusor to expose the screws, tighten them down, and the problem should be fixed. Total repair time should be under 30 seconds.

SOURCE: descaling a delonghi magnifica ESAm04

I had this problem too. The instruction manual says to turn the steam knob only half way counter-clockwise after pressing the button for 5 seconds, but you need to turn it ALL the way to have the procedure start (at least, that was the solution with my machine). Good luck!