1st thing I'd say is to check the fluid level in the power steering reservoir and also check how dark the fluid is
if its anything other than dark red then replace it and ensure that you work the steering from lock to lock to pump out the old fluid 1st
with the fluid out of the pump I'd also turn it over by hand ( after removing the belt) to feel for any tight spots on the pump, there should be none
if in any doubt replace the pump
Thanks for that. What I should have mentioned was that the pump was replaced by a garage only in March and was then fine up until about 10 days ago.
that makes a difference
I'd still try popping the belt off and feeling the pump for roughness as its quite possible the replacement part isn't right but the fluid should be clean
I'd also check the condition of the belt as these can also generate noise when worn
if it has any cracks on the belt or looks shiny then replace it
OK, great. Any thoughts as to why the problem occurs after higher speed driving in particular?
I'd say that high speed = high engine revs so the pump has to spin fast for a long period
Makes sense. Thanks Matt.