Here’s how to replace it successfully. Please read the entire instructions below before starting.
wrench adjustable to 17mm
5 mm Allen wrench
Unplug the machine and wait for it to cool down completely!
Remove the drip tray and reservoir.
With the Phillips screwdriver, remove the four screws (shown in the picture below) holding down the top cover, (some models only have two screws) and remove the top cover.
The steam valve is located at the top of the boiler. It is brass in color and leads out to the right of the machine. The image to the right shows the steam valve highlighted in red.
Remove the steam knob on the right of the steam valve by pulling it out and away from the side of the machine.
With the 17mm wrench loosen and unthread the nut that holds the steam pipe to the valve the wrench will turn from the left to the right.
With the 5mm Allen wrench, loosen and remove the two Allen bolts that hold the steam valve in position and remove the steam valve. The valve may be stuck in the boiler so you may have to pry it off with the straight screwdriver.
If the o-ring did not come off with the steam valve, remove it from the boiler opening.
Clean the opening on the boiler to remove any calcium buildup. Be careful not to scratch the sealing surface.
Remove the plastic collar from old valve and transfer it to the new steam valve.
Install the new steam valve with new o-ring and reinstall booth the Allen bolts loosely. When both bolts are installed, reinstall knob.
Center the steam knob in the opening and tighten down the steam valve bolts.
Reinstall the steam pipe and tighten the nut.
Reinstall the top cover, and replace the reservoir and drip tray.
Plug in the machine, fill with water, and enjoy espresso!