Thank you for your help and advice, will re-fit the new pump and try bleading again but this time with new suction pipe from the tank. not sure if this will work so any advice would be much appreciated. Thanks again.

Got a Disco Td5 that makes a noise from the PAS pump. Fitted new pump and water pump as well as new belt and idler or belt tensioning bearing. Blead system and noise went away. Noise is back each time after running for about 10 minutes at idle. The PAS works realy well but makes a noise even...