Assuming you don't have a brake line leak, master cylinder is the probable suspect.
I've had both situations at different times. Brake line leak sure felt the same, but the puddle in the parking lot told a different story.

On Aug 28, 2012, at 10:33 PM, Mike Miller wrote:

> Took van in to have AAZ replaced with TDI.
>
> Brake pedal is slowly depressing when held. I'm assuming this means master
> cylinder? If not what could it be [ four wheel disks on van]?]]
>
> And where's the best place to buy master and slave cylinders?
>
> Mike
>
>
>
> ________________________________
> From: Rocket J Squirrel <camping.elliott@GMAIL.COM>
> To: vanagon@GERRY.VANAGON.COM
> Sent: Tue, August 28, 2012 7:12:57 PM
> Subject: Re: What did you do for your Vanagon this week?
>
> Hugo, do you use solar panels? The Anderson Powerpoles (Google that
> phrase) are the connectors I use to connect my solar panels to my van's
> solar controller which charges my house battery, which I use when camping.
>
> --
> Jack "Rocket j Squirrel" Elliott
> 1984 Westfalia, auto trans,
> Bend, Ore.
>
> On 08/28/2012 06:51 PM, Varotto Hugo wrote:
>> Rocket,
>>
>> Could you please post a picture of your Anderon Powerpoles and how
>> they're used? I'm not able to visualize the setup you're mentioning
>> (I'm trying to find how to replace the for me useless city water
>> connection also)
>>
>> Thanks
>>
>> Hugo
>
> [snip]