Viessmann boiler failure

[boater sam]

Easy, remove and flush with a hose through both ends, invert and fill with water. fit 2 bungs where the valves were. stand the right way up, remove bleed screw.
Get a snap in rubber tyre valve from a tyre depot, use that in your tyre pump holding it against the bleed hole and pump it up.

You will soon find any pin holes!