hi,
i found some oil coming to the top of my expansion tank

, thought the worst

damn so took it bak to the garage, when my rad was leaking they replaced it with a 2nd hand one which i agreed to as they had one in stock so i thought thats fine.
there was some oil in that rad and its all come up, they didnt clean it out

, theres no oil in the system just a bit on top of the expansion tank. any idea how i could clean it out?

?
all help appreciated.