I've got to a point where I'm properly a-scratching my bonce. I've bled the brakes once the conventional two man method, and twice with a pressure bleeder (awesome bit of kit, best thing I've bought in ages!), and I've even replaced the master cylinder, but still spongey.
I've gone through two bottles of Dot 5.1, so the lines are clean and there are no leaks. The springs on the calipers are in place, no kinks.
The problem is, the brake pedal is rock hard when the engine is off, but soft as sh*te when it's running. I'm looking at the servo as we speak, do these leak air at the pedals, also there is a bit of rust behind the m.cylinder, not much though.
It must be the vacuum, but I've been told it's not. It's pretty obvious it must be, can someone advise??
"C20 LET bang"