5k1 103TDI Soft Brake Pedal

[hamish71]

Not my car. Owner says it has been this way for a while.
Per title, brake pedal is soft. Discs are worn but still in spec. Rear pads have about 70% material left. Front pads are new. No obvious brake leaks. Bleeding with engine off gives no air through bleeders, but as soon as engine is on, pedal is extremely soft. Brakes do still work but right at the end of the stroke. Have also tried bleeding at the ABS pump. No air, no change in outcome.

Is there something I am missing?

[Lucas_R]

Sounds like the brake booster is faulty/leaking and/or you have a vacuum leak somewhere on one of the vacuum lines.

[MIG]

As Lucas said above, it is most likely a failed booster. One thing to try is the ABS bleeding basic settings that can be run via a scan tool like VCDS VW Golf 5 VCDS-VAG Brake pump bleeding - YouTube

That will run the ABS pump and solenoids to ensure no air is stuck in the module.

[Umai Naa!!]

Also consider the vacuum/tandem pump.