I've got a B5 1.8E (Non-turbo) that's been left mostly unused for two years. Aside from the brakes, the car is running perfectly fine.

The symptoms are:
- The brake pedal has little to no resistance and resistance doesn't increase with pumping.
- There's no movement at all in the brakes even with the pedal fully depressed. Naturally, this means there's no braking in the car save for the handbrake.
- With the engine running, using the brake pedal leads to a strange sound of hissing air. The pedal is silent with the engine off.
- The brake booster / servo appears to be functional as the brake pedal becomes even softer when I switch the engine off.
- A brake bleed of about 40mL in total from all four calipers hasn't had any effect.
- There appears to be a ripped vacuum hose in the engine bay that I found under the air intake pipe. I can't find where it came off from though.
- Brake fluid reservoir is full and brake fluid appears quite clean.

Brake pedal hiss (Engine running)

Ripped vacuum hose

Anyone have any ideas?

 

Try bleeding them more. It sounds liek air in the system. Make sure the booster line isn't the one broken.

 

I'll try bleeding them again. As for the booster line, i've honestly no idea. I've got the assembly manual for the car but it's hard to see where the line ends.

 

Bleed the brakes more, 40 ML is not even close, 1 liter to bleed the system is more likely. The hissing may be the brake booster, make sure the vacuum line to the booster is good

 

The booster line goes though the firewall and should connect to the y looking valve or somewhere in that area, its just a vaccum line.

 

Does it have anything to do with the line in this video I took?

 

The best I can make out from the videos, is that the fat vacuum hose to the powe brake booster has a hole in it. If that is the case the brakes won't work too well.

 

Tried to bleed the brakes again at the furthest caliper. Even when pumping the pedal there's very little pressure in the fluid coming out of the bleeder screw, it literally just drips up like a faulty tap.

I'm also fairly confident the servo/brake booster is working as the pedal noticeably softens when I start the engine. With the engine off, the brake pedal behaves like the clutch. Not a lot of resistance with a fast return to its starting position. With the engine on, the brake pedal is spongy and slowly returns to its starting position.

Could bench bleeding the master cylinder solve the problem? (How would I go about it?)

 

Forgot to mention. The engine takes a tiny bit of throttle to start. When it does it's perfectly smooth but if I brake within the first ten seconds, the car starts sputtering, the idle rpm drops and it cuts out.

 

See if you can perform a vacuum leak test and/or hook up a vacuum gauge. You could have a leak causing the starting issue you've described.