Peugeot 306 HDi brake problem

[Skyedriver]

The car knows my wife is ready to sell it.....
Start the car in the morning (or evening after work) there is normal brake pedal and pressure. After one or maybe two uses (reversing down the path) the pedal goes rock hard, right at the top of its travel and requires more pressure to stop. ie no servo. After about half a minute the pedal returns to normal and everything hunky dory. (Wifes story is slightly different in that she keeps stamping on the pedal until it "releases" - I think she's continuing to empty the servo but cannot get her to accept that).
A there is normal pedal a first I think the servo is holding its vacuum and the pump is failing but surely if it fails it fails? Taking the hose of there is suction but not huge amounts. (I'm not a deisel servo expert so unsure what is right).
Looking for clues here...

[theshrew]

Yes if you take the hose off you should find sucky sucky same as a petrol car.

[mk2 24v]

sounds like a vacuum pump issue. in my time at a dealers there were a few of the diesel engined pugs that had problems with the vacuum pump

[Skyedriver]

replacing the pump tomorrow.....