My friend in ga with a refurbished 84 westy had just installed a new master cylinder and found it too leak fluid in the booster.  I second checking at the master. 

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Joel in Rochester NY
73 Westy 
87 Syncro
89 Syncro Westy

On Mar 2, 2012, at 4:33 PM, jules <jules.herr@GMAIL.COM> wrote:

> Perhaps it's leaking into the brake booster housing. was the master
> cylinder replaced with the rest of the system overhaul?
> 
> One way to see is to stick some clear rubber hose into the lowest part
> of the body of the booster (go in where the vacuum booster line
> attaches) and apply vacuum to the hose and see what, if anything,
> comes out of there.
> 
> 
> jules
> '75, '78 westies
> troy ny
> 
> On Fri, Mar 2, 2012 at 4:19 PM, craig cowan <phishman068@gmail.com> wrote:
>> Before comissioning my '90 automatic bus back to the road, the entire
>> brake system was gone over
>> The system works great. The pedal feels firm and everything seems to
>> be working properly.