After taking apart the sight glass last night on the Astoria Argenta AEP-2, I came up with a few questions. I think the assembly is fairly similar across the board for machines that have one . . . a tube of glass with a ball that is supposed to float on water. The loop, for lack of a better word is a connection at the bottom half of the boiler and one at the top.

I pulled it all from the frame and where it attaches to the boiler, disassembled, cleaned, checked for blockages in the lines, found nothing and put it all back where it came from. I noticed that the red ball is small enough to get caught in the bottom elbow. Is this possibly the wrong replacement part put in prior?

When I refilled the boiler (I did take a peek into the boiler this go round and happily found no scale whatsoever) for a short period of time, the water level in the sight glass was at the full mark, but no ball floating. Shortly after, the glass was full, top to bottom making me think that if the ball were free, it would be up in the top elbow, out of sight again. Shouldn't the water level balance based on the water level of the boiler? What else could be going on here?

There are normally screens between the balls and the fitting to prevent that from happening

The water level balls on my CMA machines have, at times, taken a leave of absence from the sight glass. Most recently in a machine that was moved up a flight of stairs. It popped back out a little while later. No idea where it went. One of my other machines just doesn't have one. You can still see the water level.

The ball can definitely fit in the bottom elbow and I have not seen one with a screen although it wouldn't be too hard to put something in there to keep in the glass. I don't know if there is a bigger ball option (insert joke here). If you made it bigger, I would worry about potential blockages somewhere else. You know that law of unintended consequences...

The water level in the sight glass is reflective of the water level in the boiler. Barring a change in physics or some sort of one-way valve creating itself in there, it has to be.

How did you fill the boiler? With the manual overfill and line pressure or with a pump and autofill circuit?