Hi Guys,
I just wanted to thank you all for your input and provide the, eventual outcome.
In short - it was the butler what done it! So...here goes my sorry tale.
To date we (this is the royal ‘we’ you understand – the mechanic has done these things!) have done the following:-
Established that the front brakes lock on but the back turn freely so we
Replaced the master cylinder. – this didn’t work. Then we
Replaced all the hoses.
And rebuilt the front calipers.
The brakes continued to lock on. They do this after about 2-3 miles. And it’s serious, you can feel the car working against them.
Disconnected the servo, which seemed to solve it, so we
Replaced the servo.
Checked the valve from the engine to the servo
Ran the car without the rear brakes connected to see if they were causing back pressure.
All of this has not solved the problem an we have now concluded that the replacement master cylinder is faulty and are putting another one on.
This last line is the key point. The AP master cylinder is incorrect. There is a faulty batch out there - Grrr!
The front port in the master cylinder had been drilled incorrectly so it wasn’t letting brake fluid back through after the pedal was lifted. Well it did, but very slowly.
We found this after the mechanic dismantled the master cylinder. It turns out there is a faulty batch of AP cylinders. We replaced with a Powertrain cylinder and all is resolved – finally.
Once again thanks for all your input.
Ian
