VW BORA 2002 brake issues

Hi all, new to the site and first post so here goes.

My dads BORA 1.9TDi 2002 has miserably failed its MOT. One item was that the brake fluid required changing. To be honest the fluid was okay just a dark blue so potentially was okay.

Anyway I replaced the fluid with new DOT 4 brake fluid from TPS, clear fluid never seen that before.

Anyway I bled the clutch first then did off side then near side one Calliper at a time front to back. I know this possibly isn’t the correct order but didn’t have room to diagonal bleed.

My dad went a little crazy pumping the brakes and the fluid came through full of bubbles at one point. Anyway got him to slow the pumping and was using a tube with one way valve so no return air could go back up. After the work the pedal was no where near as firm as what I would expect it to be.

Gave up for the night and he came back tonight and I bled the brakes again and managed to get some air out of the system.

However there is an awful lot of travel on the pedal. Way more than I would expect to be. I just drove the car performed and emergency stop and the abs kicked in and worked.

However I know in my heart there is too much travel on the pedal and there is definitely no air in the brake lines.

I’m now thinking somehow the master cylinder has failed whilst replacing the fluid. Is this even possible?

The pedal previously was firm and if you caught it with your foot by mistake you would almost go through the windscreen.

So my thoughts are it’s the master cylinder

Or somehow there is air trapped somewhere else in the system. I have a pressure bleeding kit and am wondering if to hook this up and bleed the system again. But I can’t see how this will change anything as I’m convinced the brake lines are full with no air.

Any advice welcome. Hoping someone posts with a simple fix like there is a bleed valve on the ABS unit or something I’ve missed.

You have pulled air into the master cylinder and ABS pump which will now require a computerised pressure bleed. To do this you will need a suitable diagnostic system such as VCDS, a pressure brake bleeder (max 1 Bar) and a decent battery charger as the process draws a huge current. There are two possible systems fitted, the Mk20 and Mk60, the former is a real pain in the bum to do, the process contains 17 steps which you must rigidly follow or the ABS light will come on with a fault code that cannot be cleared until the process has been carried out correctly. In each stage of the test the screen will instruct you to press and hold the pedal and it does mean HOLD as it comes back with enough force to lift your bum out of the seat so unrestrained the pedal system can get stressed. We have also found some extra steps at the start and end using the diagnostic output tests function which improve the results. At the end you must take the car for a careful run where you can achieve a speed of around 30mph and fully apply the brakes a couple of times to trigger the ABS which will finally bring the pedal back to feeling right.

Like Crasher said but have you checked for any bleed nipples on master cylinder? I have seen them with two bleed nipples on master cylinder, bleed these first then the furthest to the nearest. From the master cylinder.

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Yes quite right, I forgot that bit. There are two 8mm AF bleed nipples sticking straight up but they are impossible to get a spanner and bleed tube on so all you can do is use a very deep 8mm 1/4” drive socket and let the fluid flow and then rinse it clean after.