Viessmann boiler failure

[ppppenguin]

The problem with rads is not knowing if they're bad. I fitted most of them myself when I moved here in 1998. They are all the Barlo or similar round top types which can't be fitted upside down. The system has always had inhibitor in it since I've been here. There are 3 older rads that I kept. One is a custom curved thing in a bay window.

I don't have a pressure tester. Any simple way of improvising this, perhaps with a car tyre inflator?