I have an Astravan G 1.7 DTI 2001 The brakes are very heavy to operate. There is plenty of resistance, but requires excessive effort to brake. I can get the bonnet to dip under braking and it does stop quite quickly and in a straight line.
The problem is the effort it takes on the pedal and under no circumstances can I get the weels to lock up (non abs brakes)
I feel that it is the servo or the vacuum pump at the back of the alternator that could be at fault. The pipe from the pump to the servo looks good and the other smaller pipe from the pump seems to disappear at the back of the engine low down.
I would be grateful if anyone else has had this trouble and can suggest the next step forward.