Brake Bleeding Problem

Can anyone help me with a frustrating bleeding problem?
I've just replaced all discs, calipers and flexi-hoses on my 1997 Discovery but cannot get any pressure when attempting to bleed conventionally. I've even bought one of those Draper vacuum units but still no success! Two litres of fluid has passed through the reservoir so far and the garage is about to get a call.
I can only think that either the master cylinder or servo is shot but things were fine until I decided to replace the brake system.
Any suggestions??

They can take quite alote of fluid just kep going.

Is the Draper think like the eazy bleed where you basicaly addpresure at the resivoir end?

its possible that the diaphram is split in the servo, have you lost any fluid? it can disappear into the servo.
master cyl is a favourite though, for bleeding problems.

Thanks for the reply, the Draper kit fits onto the bleed nipple and creates a vacuum using an air compressor thus sucking the fluid through the brake system. One and a half litres of fluid already but I'll try again tomorrow.

Thanks

I seem to be getting equal amounts of fluid through the system but I will try to measure more accurately to rule this one out.

My old Rover SD1 had a similar problem, and I ended up just gravity bleeding. I got four bits of hose on the bleed nipples and four cups to catch the drips and opened all four bleed nipples and put almost a litre through it. Closed the front ones and let the back ones flow, then closed them. Started up the engine and after a couple of pumps she was right as rain.

I fall back on this method when all else fails, seems to work on the vehicles I have tried it on, but not done a Disco so not sure.

I truly appreciate your reply and assistance but on this occassion I have given in! The problem now belongs to my local garage, they reckon I have a damaged seal in the master cylinder but haven't stripped it yet so cannot confirm.