X type brake problems

[Norman Hood]

I recently bought my beautiful xtype, 2.2 diesel sports, such a lovely car, however, I went out 2 nights ago & a brake pipe burst, so I got it home & called AA out.

turns out a pipe was corroded on the rear & burst.

i called a mobile mechanic who replaced both rear pipes with copper Ines & bled the brakes, took it for a test drive & felt fine, within half an hour & less than 5 miles, the brakes started binding to a point they have almost siezed on, what is the reason for this?

my mechanic said it's the master cylinder, is this correct & has it happened to anyone else & what's the cure?

thank you