Hi Joseph,
Just to let you know of my experience, as a postscript. I had problems with engine overheating with my Big Six. On the advice of another member I flushed the system with Thermocure Cooling system Rust Remover Radiator Flush available from Frost Auto. The result was very good, well actually amazing, Overheating cured! For the sake of £25 – £30 you could try that.
Bob Cross