brake booster line

[surfkewalo]

I have a 79 Bay window. Changed my brake lines, disc brakes in front, pads in rear and both master cylinders. Brakes were good for a couple years. Then brakes got spongy and kind of hard and soft when pedal pushed. Not a consistent kind of feel like before. Just changed my brake booster and have the same feel. Was told it could be my booster lines which I didn't want to change it. Any help on how to do would be greatly appreciated.

[pioneer1]

Usually a defective booster gives a very hard pedal. Not sure about booster line but check the flex lines ballooning under pressure
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[airschooled]

Digging in your old posts, from 2008, you have DCNF carburetors, and only one barrel is tapped for the brake booster line…

The line runs back from the booster, a rubber hose for a foot or two, then a metal pipe straight down the left side of the car, above the frame rails. The metal tube transitions to rubber a foot or two before the engine, close to the center of the frame. Stock late bays in North America use a plastic tube that snakes to the left and goes through a grommet in the chassis. Some cars have the a valve before the grommet. Late bays should have a check valve after the chassis, and Tee into the plenum.

With your dual carbs, it sounds like only one of the four cylinders is feeding the brake booster with its vacuum. While one cylinder can draw sufficient air from the booster for occasional presses, regular brake use requires all four cylinders to participate. Most accomplish this with a balance tube, or external vacuum pump.

Every time you work on the booster, foot cylinder, or pedal, you MUST make sure the pedal push rod has proper free play. Too much and you won't get full stroke from the pedal. Too little and the pressure in the lines will never truly release, and the pedal will feel goofy.

The front vertical nipple also needs to have a free shot to ambient air to avoid awkward pressure issues. VW used a cloth braided hose to get ambient air from inside the frame, back of the driver side wheel well.

Robbie
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[airschooled]

Also, IF you have a single-cylinder booster connection, it’s imperative to have that cylinder running efficiently. A misfire or dropped cylinder will kill the vacuum signal. Lots of things can kill a cylinder at idle, that’s why having brake vacuum from multiple sources is safer as well as smoother. Check your valves, points, timing, and carb sync. Betcha your tapped cylinder isn’t firing.
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Learn how your vintage VW works. And why it doesn't!
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[surfkewalo]

Thanks. Will check on all stuff involved. Aloha