Brake failure???

Hey guys,
 
after toiling away to get my mk2 escort back on all fours, my brakes have failed on me.
 
I've fitted new caliper pistons and caliper seals, new goodridge braided lines and I've taken off the master cylinder reservoir to give it a good clean. All connections are good, no stripped threads, no leaks.
 
I'm experienced in bleeding brakes - use a long hose on the end of the bleed nipple to do the job. As the whole brake system was empty there was  a lot of air to push out first. Although the rears are now fine - got all the air bubbles out - the fronts seem to be sucking in air whilst bleeding!
 
That is to say, when the pedal is depressed, I can hear a sucking/whooshing noise and no matter how many times I bleed, I keep getting bubbles appear in the pipe towards the end of the pedal depression!
 
I should have inspected more closely whilst I had someone here to press the pedal for me, but it kinda sounded like the whooshing air noise was coming from around where the yoke goes into the back of the brake servo. The servo is a reconditioned unit, and with the engine off doesnt really have a function anyway.... does this mean my master cylinder needs a rebuild? Could it possibly be brake differential valve too??
 
Cheers
 
Nick

If its an older mc and you did a full stroke on the pedal you just toasted the seals. You never depress the brake pedal to the floor on an older mc. The piston never travels the full bore length. That part of the bore gets crusty. When the piston travels through there it tears the seals up. Very common mistake.

Thanks for the words guys,
 
Matt I will try your method of bleeding the next time round - will save me hunting for a partner to pump the brake pedal for the third time :) Thanks!
 
Spigot - thanks for clearing that up, I did actually do that before I put the calipers back on, so that would be the answer to my woes then. Theres a great brake shop here in WA (Hitec Brake & Clutch in Wangara) who will match up seals for me tomorrow.
 
Gdub - hahaha yes I made sure the nipple was up top. thanks for thinking outside the square. It does happen :)
 
Cheers guys, let you know how it goes. Got some pics together, so build thread will go online soon.
 
Nick