Itinerant Air-Cooled

There must be a GAP between brake pedal linkage and booster "push rod" (actual name is "connecting rod", but hoi polloi refuse to use that term.) There's a threaded end on the pushrod with a locknut for exactly
that purpose. (See Sect. 4.1 in Brakes&Wheels chapter in your Bentley manual). If you have the gap, and it's hissing continuously (normal to hiss on pedal letup), then your new, clean, booster is DOA.

The diaphragm itself is sturdy, and rarely fails. It's the plastic and small rubber bits inside the valving that go out, and possibly corrosion from H2O in
the brake fluid if it's allowed to accumulate in the booster.

Thanks much ! Ill look into that today....

dingo wrote:cant remember how to post images

Offsite host picture is www. blahblahblah.jpg

then highlight address and press "IMG" button in your reply window toolbar.

[ img]www.blahblahblah.jpg[/img ]

It took me almost as long to post a picture, as to install the exhaust system in my '78 Westy.

Discovered the source of hissing/leaking with listening tube; the booster unit is not as robust as it appears. The fit was tight, but ok on the drivers side..what I couldn't see was that the factory metal conduit was causing clearance issues at the top of the chamber..not much, but enough to squeeze the circle into a slight oval...tight fit on driver side kept it intact but direct opposite on pass. side squeaked open just a hair. Futurely, maybe drill out the four bolts holes just a skosh*. Anyways, silicon glued the crack and it seemed to hold its own during idle and during braking. The later models are differently crimped than the early ones, so not sure if the rubber diaphragm has lost its seating with the installation tweak..and whether it will return to normal if unsquished ! ... so far seems to brake.

The '71 model is ready to put back together after thorough de-rusting and cleaning..but I noticed that the main seal , much like rear main oil seal, has a circular spring which uncoiled itself..so I need to replace that

*skosh
"a little bit," Korean War armed forces slang, from Japanese sukoshi "few, little, some."