Brake Booster Hiss?

[VanGeek]

My 01 weekender "Vanna" gets very little use during the Northeast Winter months. Took her for a spin a few days ago and noticed a hissing noise from behind the dash or engine compartment for a few seconds after I remove my foot from the brake.

So... No noise while normal driving. No noise during braking. After removing foot from brake (either starting from a stop or shutting off vehicle), there is a faint hissing noise that lasts a few seconds.

Engine runs fine. Brakes work fine.

Not sure what's causing it or where it's coming from. I assume it's related to the brake booster but am not certain. Before I diagnose the mysterious noise, do any samba eurovan experts have recommendations for what may be causing this?

[TheOneTrueQuux]

[VanGeek]

OK I thought that was the issue, and would like to replace the booster before it fails. Haven't previously swapped a brake booster but it seems fairly straightforward.

However, in our later model eurovans the brake hard lines pass right in front of the booster and seems like it will be difficult to get the old booster out without disconnecting and moving them. Would prefer to push them far enough out of the way to make room for the booster but am not certain that's possible without breaking or kinking them.

Any wisdom and tips from forum members that have swapped the booster on later model Eurovans with all the ABS and brake line hardware?

[VanGeek]

Pulled the booster. Was hoping to keep the brake & ABS hard lines intact since another member here reported they were able to push on the lines and squeeze the booster out. I didn't see a way to do that without severely bending the lines so I disconnected them.

Booster is out, and I've observed that the foam on the inside is very crumbly and *I think* might be damp as well. Examined the inside of the booster and the bottom metal on the inside appears slightly wet/shiny. Lastly, there is some rust and bubbled paint below the reservoir on the outside of the booster. So it's likely that the master cylinder has a small leak and should be replaced.

I've seen a raybestos cylinder on rock auto and amazon that is ~$75-80 shipped. FCP Euro has an OEM version made by ATE that is $244. They both look the same as the one I pulled out, although the ATE has the same numbers marked on it.

Anyone have experience with raybestos master cylinders vs OEM? Price difference is over $150 so I'd like to hear from others that have experience with this.

Hard brake lines detached and booster + master are out:

Foam is crumbly and possibly damp (from brake fluid?) on original booster

Evidence of possible brake fluid leaking down front outside of booster as well.

Booster and reservoir removed. Was gonna reuse but will now replace cylinder: