try a bit of a power flush with a hosepipe via the feed pipework
Yeah,I did that in both directions and it seemed pretty clear. Will try again this weekend (weather permitting) to see if I can get rid of any airlock.
"Y mae dafad ddu ym mhob praidd" 1972 4/4, 1981 MGBGT, 1984 FLHT1340, 1980 XLH1000, 1990 ZX10