i cleaned up both front brake calipers and replaced the pads,i pushed the caliper pistons back as i normally would,i reassembled everything without disturbing the hydraulics,when i pumped the pedal to bring the pedal back up there appeared to be a clicking noise from around the master cylinder.When i started the engine there is hardly any brakes whatsoever,there seems to be a hissing noise from inside the car when the pedal is pressed,there is a full pedal there but nothing happens,please help as i'm supposed to be going on holiday in three days.by the way it's an 89-740.

The hissing from inside the car indicates a hole in the diaphragm of your
brake booster (servo). I think it is coincidence that it happened at
the same time that you replaced the pads, although if there is brake fluid
inside the booster it also indicates the rearmost seal of your master cylinder
is also bad.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma

how can i test the servo,is it possible to do without ripping everything out?

If you are getting hissing around the actuating rod, you don't need to
test it - it is bad - got a hole in the diaphragm.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma

will i have to bleed the full system if i replace the servo?

No, you don`t have to bleed the brakes if you change just the servo.
Undo the two nuts holding the cylinder to the servo and pull it clear of the studs, gently move the cylinder out of the way by allowing the pipes to bend, do not move it any further than you need to. Disconnect the vacuum hose.
From inside the car disconnect the actuating rod from the pedal, and undo the nuts holding the servo to the body.
You can then remove the servo (you may need to un-bolt the coil bracket and swing the coil and the bracket out of the way)
Before you fit the new servo check that the rod which pushes on the master cyl.
piston has the same protrusion as the old one.
I would get a servo from the breakers yard if I were you, new ones are very expensive and, contrary to your experience they don`t fail very often.
Colin.

just a quick thought, did you look at the white check valve on your servo unit?
the sound you heard could have been it popping off, start the car and put your finger on the white check valve and see if it leaks.