How Do I Bleed a Riello Mectron M5?

Here's some more info:

The manual is worthless in that it shows NO such valve and the instructions I read here about an M3 burner just aren't clear enough given the warnings I read in other forums about the pressure regulator being in the same place. I uploaded some pics...

http://www.chronos-historical.org/burner/2.jpg

In this pic the only candidate I have is the silver bolt beneath the black one but it is described in the manual as Pressure Gage Fixing Point... not a bleeder valve. It's roughly at the location mentioned in the other post. But I want to be sure. Here's another view..

http://www.chronos-historical.org/burner/1.jpg

Thanks!

Robb
February 2009