Brake servo not holding vaccum

[Cableguy]

Righto, before I go ahead and get a replacement servo, wanted to confirm that I'm on the right track.
Mine does not hold pressure. I've checked the vac lines and installed a new vac pump(got a brand new one free!)
When I pump the brakes with the engine on, the pedal goes stiff and I have to press incredibly hard to get it to stop.
If I pump the brakes then turn in engine, the pedal does not fall away.
All this points to a failed servo I think.
Should I be looking anywhere else?
Cheers

[dave friday]

One way valve in the vac line?on mine its a little black n blue jobby.

[Cableguy]

Thanks for the post.
Wasn't totally convinced about the servo as it seemed to hold a vacuum with the engine off.
Disconnected the diff lock shiz and found a tiny crack.
New line installed and now sorted