my 1989 260e temp gauge sit a fraction above 80 and somedtimes on idle heads for 90, but soon as the cars running again drops back to just over 80.had the cooling system checked and replaced a heater hose which had a slight leak under pressure, mechanic advised slight oil leak from rear head gasket, 130000kms on clock, would it be time for valve guide replacement or would valve seals if i replace the head gasket, have been told this model has duff valve guides,would appreciate any comments , summer is coming down under and want to run a coool car.