Rear brake problem, compensator?
I took my GTV (3.0) for it's MOT on thursday and it failed on service brake efficiency - both rears recording little or no effort, got 44%, needs 50% to pass. Also the handbrake just scraped through at 16% (the minimum pass rate). I was expecting this as on its last MOT (before I got it) there was an advisory on the rear brakes and handbrake (service brake got 57% last time).
I presumed it was going to be seized calipers, so I stripped them down today to free them off; only to find that both were fine, all the sliders moving freely and the pistons wound back in easily, so I don't think they're the problem. Whilst I was there, I tried to re-set the handbrake by winding the pistons back in fully, slackening off all adjustment so they were on their stops on the caliper, pumping the pedal, then re-adjusting at the handle, although it doesn't really feel any different.
Since the calipers appear fine, I can only think the reason for the poor service brake would be the compensator valve, unless I'm missing something else?
Has anyone paid to have the compensator replaced, if so how much was it? I've checked mine and one of the brake lines is quite heavily corroded at the union, so it will snap as soon as it's moved and I hate replacing brake lines!!