Ever since my mechanic replaced the handbrake linings, there's been an annoying low whistling sound from the rear, esp when turning. Slight application of handbrake stops it. I mentioned it to him when he did my radiator work, and he pulled the handbrake drums off and had a look. Said they like fine, so he put it back together and didn't charge me. But it's still doing it, and it's starting to drive me mad.

Any suggestions for a fix would be much appreciated.