PTO won't engage with engine running - endless grating sound. Can get it to work by engaging PTO before starting engine, but it continues to run when clutch pedal is fully depressed. I've adjusted the clutch release fingers, PTO clutch and pedal as per manual but it has not helped. Problem started after winter, when PTO had not been used for months. It's as if the PTO clutch is not releasing? Any help appreciated - I'm not mechanically minded so limit to what I can do.