Surely somebody else has had this problem, I have bled my brakes at least four times now and still seem to be getting air in the system but with no leaks that I can find!
Its the standard 1200 coupe setup with new master, rebuilt calipers, new brakelines and new (ebay) wheel cylinders.
The air seen to be getting into the rear circuit, this is driving me nuts.

does it have bleed nipples on the master cylinder?

Yeah, I did the master cylinder aswell three times. Maybe its the rear wheel cylinders but there should be a fluid leak!?!

Such a simple task to do but such a pain in the butt!

Air in lines will move to higher point[not necessarily highest point], master cylinder may not have enough flow to purge line. Sometimes you may need to coax air to move by manipulating lines/calipers to get bubble to travel.You could also try reverse bleeding,oil squirt can of brake fluid connected to caliper nipple [hose & clamps]low master cylinder fluid level, crack the nipple & pump back to master cylinder.Hope this helps.

Thanks cranky, all feedback is appreciated. The master cylinder seems to be pumping OK, I've done this many times and never had a problem I am thinking dodgy rear wheel cylinders but not sure.

ik had the same problem with my ute and the mechanic at my tyre shop couldnt fix it so we replaced everything ,but it still didnt help

i might try to pressure bleed them

Everything has been replaced though! Hmm, It has to be a faulty part.

Standard or dual circuit master?

Just had a look at your build photos. If it is getting air into the rear circuit only I would be looking at the flexible brake line on the diff first. Then the rear wheel cylinders.

However if the system is being fully bleed and their is no air in the system there has to be a leak for air to get into the system as its a closed circuit.