Have found Fernox & Sentinel products will clean systems pretty well with a P F machine, F5 & X800 best, but with severely fouled systems Kamco's FX2 comes into it's own [ not for use with allumium ]. It does take longer as you have to neutralise it. Often will dose system with Fernox F3 or x400 to pre-clean.
Always use a TDS meter & ph paper to confirm it's clean & neutral.
Always use a TDS meter & ph paper to confirm it's clean & neutral.