8v and 16v brake hoses.

I would block of the fronts and wedge the compensator FULLY open and then re bleed the rears till you get solid pedal. then and only then bleed the fronts.

this really does sound like air in the system (sorry i know, but thats my professional opinion)
do you have new pads all round? i have seen that the thickness of mk 3 pads are a bit thicker than mk 2 pads by a couple of mm although the design is the same. times that by 4 and that equates to a lot of extra travel, especially if discs are a bit worn too. do you have the 16v larger mc? if not this will cause the extra travel in the pedal. heard cases of people getting it almost to the floor before it stiffens up.
do the wheels actually lock if you try and spin them when the pedals right down? if not then there isnt enough pressure in the wheel cylinders, another sign of air. I would lock off the flexi hoses and re bleed 1 at a time starting at o/s/r then n/s/r then the fronts. from what you say it is not the m/c as this goes hard with all ports blocked off. 2 man bleeding is best remembering to fully close bleed nipples in between strokes of pedal. Take nipples out and make sure they're clean and free of dirt etc on the seat. i am guessing the air is between the mc and the unions where the pipes split into two in the engine bay. every pump you move the air along and every return it draws it back up, never getting it to the wheel cylinders. only other suggestion is get a big syringe and reverse bleed them, forcing fluild into bleed nipple, this is the way we do motorbikes as the front brake lines are nearly vertical and its a right sod to force the air down to the wheel cylinder due to the short stroke of the mc. gravity seems to let the fluid pass the air and leave the air above the fluid.

Alternatively bleed at each union along the lines in order just crack them open and see that fluid comes out air free, So 2 unions in engine bay, then compensator in and out then wheel cylinders.
Also pump pedal hard before you start to bleed this may help. you could also try wedging pedal down over night with a bit of 4x2 and see if this will help force air either back to mc or to wheel cylinders.

Keep us all updated as im keen to find out what the problem when this is sorted.

 

ok another thought just to try, take calipers off car 1 by 1 and with help of friend pump pedal so pistons move out but not all the way or they will drop out. with pedal on the floor crack open bleed nipple and push caliper back. if no aircomes out, then air is in the pipes if air comes out of the nipple then you making progress, when no air on any cylinders re assemble and bleed again. you wanna make sure all the cylinders are free of air before you bleed the pipes of you will just keep going round in circles as you have been.

You have had every union bleed nipple and pipe as well as the mc off so your system will be full and i mean full of air at every possible place. just bleeding wheel cylinders will never purge all the air from the system (well not without a lot of effort and aggro, which you have already had!)

 

Have changed to mk3 brakes front and rear,had some handbrake problems but got there in the end ,just hand 6 month vehicle check we have in my country,front brakes 3% out of balance and rear brakes 5% out, that is a pass on the brake tester,I cant work out why you have these major issues??,used a one man bleeder and it was very easy.
The only reason for a soft pedal is air in the system or old swollen brakelines,are all your calipers free and moving?,sorry I can't be more help as you may getting fairly pise#d off by now,personally I HATE brake work.

 

When you block off the fronts and rears, that's at the M/C, right?

Other than the M/C and the front calipers/hoses, has anything else been replaced (pipes, etc?)

 

Im only using two of the ports on the MC im blocking them off at the t-pieces.

I found that the rear seal on my new MC had perished, possibly sat on the shelf too long, so ive ordered a mew seal and fingers crossed that will fix it. Should be here today.

 

Probably worth mentioning i am using paralel ports on the MC.

 

Right so the new rear seal came today and as i eas bench bleeding the MC it popped and let a shed load of fluid past it onto the shaft. Damn repro parts! :angry:

So ive put the 20mm one ive got on as i know it works and the brakes all bleed up lovely with all the air coming out nice and fast BUT after going round the car 4 times to make sure the air is out (fairly confident it is as the fluid level isnt dropping too sharp in the bottle) the pedal still goes to the floor with the engine running, theres literaly nothing there!

The MC is good, all the flexis are good, the servo is good, the callipers are good, theres no kinks in the hard lines and the compensator works fine. What the bloody hell is going on?!

 

You need to try and isolate it (again - sorry) to one part of the circuit. Block off the front feeds at the master cyl, or the nearest possible point, and see if can get the back to go hard and stay hard when you try the pedal. Then you try the same thing with the front.

 

Ive just done that and each time i block the fronts or backs off it stays hard. Connect it all up again and back to square one.

 

Good grief! Same with and without the engine running?

 

Yep. Its really puzzling.

 

Been through all the tricks people have suggested now and have found pressure will build in the pedal when the compensator is held closed but all lets go when open so i believe the problem lies on the compensator or the rear flexi hoses.

Might aswell replace everything at this point.

 

Ive now replaced the compensator and bled the system, no air coming out of any nipples and a good flow of clean fluid but still no preasure in the pedal.

 

Ive now replaced the compensator.
I disconected the fronts and bled the rears, pedal was rock hard.
Reconected the fronts, bled all 4, pedal still rock hard.
Started the engine, pedal goes to the floor with no resistance.
Stop engine, destroy vacuum in servo and pedal is solid, wait ten seconds and pedal goes to the floor.

Put the 8v brakes back on as i thought the 16v ones were no good, and the problem persists in the same manner.

So tomorrow's jobs list is:
Replace the two lines going to the front flexis from the t-pieces
bleed with fronts blocked
bleed with all 4 on and see what happens

 

I'm not sure how the servo could cause that, but it sounds like it's related... I've never had a problem with one on a VW myself, although I changed a faulty one on an old Jag for a mate.

If you disconnect the vac pipe from the servo and block the engine end, what happens?

 

Same thing happened, pedal still goes gradualy down with the engine off and falls to the floor with the engine on.

 

Right, i finaly got the balls to risk disconecting the rear lines at the t-pieces, and bingo bongo the pedal is rock ******* solid.

Bloody typical.

 

progress then!!, we have established that pedal goes hard with compensator closed, so its air in the rear calipers, lines or a bulging rear line as suggested earlier. or a knackered caliper seal but cant be latter as no fluid leaks!

 

Gone back to the car today to try again. I disconected the two lines going off the compensator to the callipers are blocked them off and the pedal is still hard so its defiantly from there onwards.

I took the rear callipers off and held them upside down and the right way up (just to try everything) and bled them, no joy. The flexi's arnt bulging so much that you can feel them do it. but would you be able to feel them bulge? At this point im considering driving it without the rear brakes but that as we all know is just a terrible idea.