Indeed it is - look under the N/S rear wheel arch area - follow that pipe it should lead to a small plastic cylinder which is a none return valve. Follow the pipe to the front of the van where it leads to a Vacuum chamber ( a large disc shaped object and that connects to the Master Cylinder under your Drivers seat (on RHD model) It is worth checking that Vacuum pipe is in good condition all the way along, I replaced all of mine last year and now I have brakes that work!
