New caliper brake pressure mystery

[timmo]

A happy Christmas question for everybody:

I have what was a fully functioning mk2 golf rear disk conversion on my GTX. All was fine, until having replaced the old calipers with new ones I couldn't get any pressure in the system after bleeding.
Assuming it was the master cylinder (it is a 22mm bore), but not sure, I took it to the garage.
They confirmed it was the MC and replaced it.
Now despite bleeding it many times, manually and back bleeding, they still can't get pressure in the system!
Their last resort was to remove the pressure regulators going to the back brakes.
Before closing for Christmas this morning they called me to say its not ready yet, so either the regulator trick didn't work or they've not tried it yet.

Anyway, I'm stumped for ideas, as are they. Other than the new calipers being shot (they aren't leaking any fluid though) I can't work out what could be wrong!

Does anyone have any suggestions? I've got a week over Christmas to ponder it.

Thanks and merry Christmas!

[scala92]

Rear Calipers on the right way up with bleeders on the topside?

[timmo]

A good suggestion, but unfortunately they are on the top. That said, I wonder if it's worth unbolting them and moving them about to see if any air is trapped in there? hmm
Thanks for the help, I'll let you know what happens when the garage open up again on the 2nd. I should have kept it for myself to fettle with.. oh well.

[timmo]

Well, I'm an idiot. Although the calipers were put on the same way as the old ones, you were right scala92. The stupid design has the same location of brake pipe and hand brake cable, but the bleed nipple was on the bottom. I was looking at the old calipers when trying to remember which way round they were. It took a bit of explaining to the garage mind. I told them just to rotate the calipers when they bled the system and then bolt them back on in the same position. It worked perfectly.

So yes, although the aftermarket calipers appear to be well built, design wise they're a little poor (they are intended as direct replacements, and the hand brake cable is too short to reach the underside, if they were switched).

It only cost me a new master cylinder, and about 50 litres of brake fluid haha

Thanks for your help, I should have applied my brain rather than the brakes! Still, you learn eh?

Happy new year everyone! :)