Ascaso Uno Repair: Leaking Heating Element and Fittings


This web page shows how to repair a leaking heating element of an Ascaso Steel Uno Pro PID boiler (late 2011 production date). As this espresso machine was about five and a half years old and started leaking on the top of the boiler (noticeable from the outside by a hissing sound), it was decided to try to repair this at home instead of handing it over to a repair shop. In the end, the repair is fairly easy for the tech-savvy. This web-page is intended to show how it's done, and keep your espresso machine up-and running.

Ascaso boiler leaks by the heating element and fittings


The tools needed are common, see picture below: a 10, 13, and 17mm wrenche, and a long and short 3mm hex key. The latter is needed to loosen the boiler flange screws at the back of the flange. The boiler can be removed fairly easy by loosening the front switch cover. The electrical wiring does not have to be disconnected from the front panel, but tie-warps fixing the wiring may need to be cut. The operation takes less than two hours, from start to finish. According to the sparepart supplier, Ascaso changed material of the heating element packaging, which are now said to be Viton seals (red in color). For the fittings connecting the water inlet and steam outlet to the boiler, teflon (PTFE) tape was used during reassembly, although thread lock glue was adviced (but not available in hardware stores). These fittings appear to be tapered threads towards the boiler. Usefull to know: this repair was done within two hours time without prior knowledge of the espresso machine. So labour cost can be estimated when this repair is handed over to a repair facility. The risks are however that the heating element is damaged during removal when the nuts are too tight, or that there is heavy scale buildup. In that case, or as a precautionary measure, a new boiler can be installed instead. Tools used during the repair

Reparing the boiler heating element

Below a set of photo's showing the steps to repair the leaking boiler seals.

Warning: electric shock safety hazard. Only skilled people can perform this repair and relies on workmanship and proper training. The boiler heating element terminals are unshielded, and water can be spilled per accident.

The front panel removed to access the boiler flange screws. Note the bowl to catch the water inside the boiler: The front panel removed

Now with removed boiler. Note the pipe, which shows the top level of the water inside the boiler is used during extraction: inside view of the grouphead of the Ascaso Uno

The boiler, which shows no scale buildup, so cleaning regeme is ok: boiler bottom side Ascaso Uno

Disassmbled heating element: heating element removed Ascaso Uno

The culprit (aka root cause): dried out o-ring seals. note the crack on the right: heating element with dried-out o-ring seals

Heating element with replaced o-ring seals: heating element with dried-out o-ring seals

Also the sealing of the fittings were leaking caused by cracks in the material due to aging: aging seals

Same root cause: aging seals

All re-assembled, with teflon tape used to make the fittings of the water inlet and steam outlet leak-free: aging seals

As good as new: Ascaso Uno Steel Pro PID front view