THE brake story...continued...HELP!

[imported_brackie]

OK, so I got all of the air out of the brakes. Pedal is nice and hard. Then I start the motor. Pedal goes to the floor. Again, and again and again. Servo was fine before replacing the master cylinder. Switch of the motor and I've got brakes again. Any ideas??

[Volksfolks]

How did ya go bud, got me thinking hey,

Andy

[imported_brackie]

Busy day today so not time to look at the car. Well...I looked at it but that was all! Got a funny feeling that it could be either air trapped in the secondary piston (diagonally split braking system) or the master cylinder that I got had some kind of insert missing from it's push rod. The only way to check the latter I guess is to remove the master cylinder and compare it with the old one.

[Golf Loon]

I`d bleed the brakes before taking it apart again.

[imported_brackie]

I've got clean, air-free fluid coming from the bleed nipples (used different coloured fluid so I would know when it was thru') so I'm certain there's no air in the system...But wait! What do you reckon about the pressure regulator to the rear brakes? Could there be air trapped in there? If so, how do you get it out? There's no bleed nipple.

[Golf Loon]

I think the regulator is too simple for that. It just adjusts braking proportions dependant on load. As long as the angle of the car wasnt changed, sholud be unaffected. I`d put a bottle of fluid through the system to be sure its all bled up. Other than that, your taking the master cylinder apart again

[imported_brackie]

So I bled them again...... Lovely hard pedal with just he right amount of travel. Then I started the motor. Pedal to the floor. So it looks like the master cylinder comes off tomorrow and then what???

[Golf Loon]

Sounds like a bad booster

[imported_brackie]

So I took off the new master cylinder to compare it with the old. Appears the same on the outside, so I looked at the (what I thought was) the push rod. Not a push rod but the end of the primary piston. The inside of the new one was drilled out at the same diameter all of the way down. The old one has a step in it about 2/3 of the way down. "Aha!" I thought.... "Maybe the rod inside the servo is the same diameter as the smaller diameter inside the old piston but smaller than the diameter inside the new piston, giving a longer length of travel." Nope. It fits down both. OK. So I take the primary piston out of both master cylinders and I find that they are of different bores! The old one is 12mm and the new one 9mm (or as close as I can measure with callipers...Wouldn't a vernier be nice?). I'm convinced that the booster (I call it a "servo") is OK. Where to next?

[Beige76]

Can you take the booster apart? How do you remove the primary piston?