Put the thermocure in over the weekend, left it in until today, including a drive to work and back on Monday.
Prior to using, I'd flushed the system back and forth, through thermostat housing, through heater pipes in both directions and radiator top to bottom for about two hours - water was coming out clear through every pipe.
Water I drained out today was black! Seems to have done an amzing job. The visible block through the thermostat housing was previously the usual rust colour, but was now very clean and no rust. It's not scrubbed it back to bare metal but made a substantial difference.
The water flow is much improved - before the treatment I put a hose on the manifold take off, and by blowing really hard could just get some air through the bottom radaitor hose. Today, if I was more talented, I could probably get a tune out of her! Air flow has greatly improved.
Just waiting for the postie to delivery a new water tap (i've decided to remove the bypass system and fit a straight on/off tap) then I'll get her topped up and check hoses.
Will probably do it again just before winter, but certainly recommend it. Thanks for all the advice.
