Vw Touran 140Tdi 2008 Help!

[205Rallee 59]

Hope somebody out there can help me

 

My VW Touran has a hissing noise which is there all the time the engine is running and then disappears when the brake pedal is pressed. I'm guessing it's a leaky pipe to the brake servo or a dodgy brake servo, although the brakes seem fine.

 

The bl..dy think has been serviced by a VW dealer with god knows how many brake fluid changes and it's only done 60k miles. Fingers crossed it's not the dreaded ABS pump failure.

 

If it's a dodgy servo any ideas how much the dealer will rip me off for the replacement? (Might ask for a goodwill reduction).