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>From: "James L. McGill" <fishbowl@fotd.netcomi.com>
>On Thu, 10 Apr 1997, WALTEE wrote:
>>About those brakes, there is an adjustment to be made between the piston
>>on the master brake cylinder and the brake pedal. By removing the toe
>>panel, you can access the master cylinder pushrod. There should be a 1
>>mm clearence between the pushrod and the master cylinder piston when the
>>brake pedal is in the resting postion.
>
>don't flame me for this please, as I have not seen this in either
>Muir or Bently, but how do you make this measurement? In my case,
>1969 dual circuit.
Good question. And I'm afraid that I don't have any really good answer to
it. The good news is that the only really important thing is that there
must be SOME play at the pushrod end. I suspect that there is a gauge used
at the factory to set up the pushrod properly for each car. This takes out
variation in the pans of each car and assures that that pan will work with
any master cylinder pulled off the shelf (given the allowed variation in
master cylinders.) This is why the manuals say NEVER to adjust the pushrod
length. I have not seen this gauge in any of the manuals I have or in any
of the special VW tool catalogs that I have. Note that both the pushrod
length and the pedal stop plate affect the MC freeplay. Without more
detailed instructions, I don't know how to set up the pedals properly,
therefore I encourage people never to adjust the pushrod, and only adjust
the stop plate if there appears to be a problem.
For reference and EMPHASIS I am going to type in the section from the
Official, German shop manual. The one I have is for the Beetle, but the
type III should be the same:
quote
...............................................................................
Operating Rod
In order to ensure that the cpmpensation port is not covered by the primary
cup when the brakes are not in use, the push rod must be set so that there
is a clearance of .04 in. (1 mm) between the tip of rod and bottom of hole
in piston.
|-------------------------------------------------------------------|
| |
| Important |
| The clearance must always be set by moving the brake pedal stop. |
| |
|-------------------------------------------------------------------|
Clearance S of .04 in. (1 mm) in the master cylinder can be measured also at
the brake pedal plate.
S=.04 in. (1 mm) is equal to a pedal movement x of .2-.28 in. (5-7mm).
An alteration of the length of the push rod ... set in production is not
permissible and must not be carried out even at a customer's request.... If
a push rod has to be replaced, the old push rod must be measured and the
length transferred to the new push rod. The measurement is taken from the
push rod tip to the center of the attachment hole.
...............................................................................
end quote
Remember, the important point is that there MUST be some play whenever the
pedal is let up. This allows the pistons in the master cylinder to come
back and be stopped by the snap ring at the mouth of the MC bore and assures
that the compensation port(s) in the master cylinder are uncovered when the
pedal is released. This allows the brake fluid pressure to come to
equlibrium with the reservoir even under changing temperature conditions. A
lack of clearance will cause your brakes to drag or lock up under certain
circumstances, but it will not affect your ability to pump up your
system--unless it's so extreme that your master cylinder is left with very
little stroke.
I have found that one of the most common reasons for no play is that the
pedal shaft/bearing is sticky and doesn't allow the pedal to come all the
way back up. The long term solution is to remove and disassemble the pedal
cluster. Clean everything off, and regrease the works. For my own cars, if
I do this, I also drill some holes and install a grease fitting. On MT cars
this requires a couple of extra holes to allow the grease to flow from
outside to the inside of the intermediate (clutch) tube.
Jim
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Melissa Kepner Jim Adney
jadney@vwtype3.org jadney@vwtype3.org
Laura Kepner-Adney
Madison, Wisconsin
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