Air in solar system

Have a Carey solar system fitted. There's a bit of a hum now coming from it, which I understand is from air after getting in. I found a tiny drip on another pipe in hotpress and this is probably where air got it.

Anyone know how to bleed it? It does not heat the rads, so I can't simply do that easy job.

It must be purged with a solar pump station. This take approx an hour or so plus connection/disconnection time. The longer the better so that all microscopic air is removed.
Of course, the leak would need to be fixed first.

Thanks. Not something I can do myself then!

Usually not, but if it was due a service this would all be included in a standard service.