4000/5000 brakes

[Bill Samaras DTN 223-7322 30-Jul-1993 0854 <samaras@wrksys.enet.dec.com>]

This is in response to a few comments about brake behavior...

4000's and 5000's tend to have completely different power braking systems. The
4000's tend to use engine vacuum (USA style), while the 5000's (and some later
cars), use hydraulic pressure from a separate hydraulic pump (Catapillar
style).

It is not "normal" for a brake pedal to go to the floor EVER. It is not normal
for pumping the pedal to change the feel of the brake pedal. 

For the pedal to feel soft, or to require pumping, it usually means one or more
of these things:
        + The master cylinder is worn out.
        + There is air in the system. This should never happen unless something
          failed.
        + There is a brake fluid leak. This should never happen unless something
          failed.
     
The main symptom of a malfunctioning brake boost (power) is excessive pedal
effort. This can be caused by:
        + vacuum leaks to the brake booster (4000/USA type systems).
        + Leaky booster diaphram (4000/USA type systems).
        
        + Leaky hydraulic booster (5000 type)  
        + Leaky pressure accumulator (5000 type).
        + Bad hydraulic pump (5000 type).
        + Clogged hydraulic return lines from pressure accumulator (5000 type).

None of this is rocket science, but lots of people drive around with bad
brakes. All you need is a Bently maunual, some patience, and a heap of $$.
Seriously, never drive around with soft brakes.

...bill