View single post by Mark Rosenbaum
 Posted: 04-28-2005 03:18 pm
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Mark Rosenbaum

Joined: 03-12-2005
Location: Kingman, Arizona USA
Posts: 532
The quickest way to test the brake servo is when the car's in service.  One brakes the car from a known low speed (a) with the servo hooked up normally, and (b) with the vacuum line from the intake manifold disconnected and capped off.  For case (b) there should be a very noticeable increase in the pedal pressure required.

In your case this won't be practical for a while, obviously, so you'll have to check things out individually.

The one-way valve should snap shut whenever the pressure on the inlet side exceeds that on the servo side by a very small amount -- basically, blowing gently through a straw at its innards should be sufficient.  If necessary, the valve can be cleaned with a mild solvent.

The sealing washer for the valve should be carefully examined and replaced if worn or damaged.  Also, check for corrosion and damage around its mounting hole in the servo housing.  If necessary, a small quantity of a flexible gasket sealer such as Hylomar can be used to assist the sealing here. 

If the servo's vacuum chamber is pumped down to 20" (500mm) Hg of vacuum, it should retain at least 15" (380mm) Hg for at least 10 minutes.  Ideally it should retain the 20" of vacuum for hours or days.

If a noticeable amount of brake fluid is found inside the servo, one can expect eventual failure of the rubber parts within the mechanism, and a rebuild is desirable.  Otherwise, however, these things seem to last indefinitely. 

If you disassemble the foot pedals for cleaning and painting, I advise comparing the location of every part to the parts book drawing.  The drawing does not correctly show the correct orientation for several parts -- ISTR this includes the brake switch bracket and pedal return spring, and perhaps a couple of other items.  If your assembly is already in pieces and you need advice, I have a correctly assembled spare unit I can look at and try to describe for you, just let me know.

When attaching the lower part of the throttle pedal to the upper part, be sure to use Grade 5 or better bolts and lock nuts, and torque these down properly (2-4 ft-lb IIRC).