Should I install a combi or keep my 2 boilers?

Hi,

I currently have 2 boilers, 1 for the radiators and the other for hot water but my boiler for the radiator keeps drawing air into the system, preventing half of the radiators to work and the boiler is roughly 13 years old. So should I keep both boilers and repair the problem or just buy a combi boiler and get the problem sorted at the same time.

Thanks for your help in advance

Should I install a combi or keep my 2 boilers?