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In
general, whenever you are bleeding an ABS-equipped Saturn you can do
so exactly as you would any other vehicle - stroke the pedal to
pressurize the system, open a bleeder, close the bleeder, and repeat.
This does not change whether you are pressure-bleeding,
vacuum-bleeding, or manual-bleeding. Just follow the same steps you
normally would for a non-ABS vehicle and you're most
of the way there.
Operative
word: most
Now, with
some ABS devices, you are actually done no matter what (Delphi's ABS
VI found on 1991-1999 S-Series Saturns, for example).
Bleed as above, and you are finished.
Note that there are some special situations where the retailer
will perform a diagnostic bleed of the early ABS units, but this is
not within the scope of this article.
Stop reading, and go get a drink.
However,
others have their own internal reservoirs (Delphi's DBC7 found on
2000+ S-Series Saturns and all Bosch ABS5.3 found on L-Series Saturns)
that are not a part of the primary brake circuit and are only opened
to the rest of the circuit when the ABS is active.
Now, if you just bled your system per the above technique and
never again cycled your ABS, you would be fine.
However, as soon as the ABS cycled - even for a few tenths of a
second - the "old" fluid (which was never bled because it
was hidden) would be dumped into the primary circuit.
Not the end of the world, but you want fresh fluid everywhere,
right?
The
“official” procedure
The correct
way to bleed the ENTIRE system, in this case, is to employ a Saturn
Retailer service tool (sort of looks like a Nintendo GameBoy) that
allows you to cycle the ABS valves and/or the pump motor WHILE you are
bleeding the brakes. In
effect, this allows you to open the hidden passages in order to purge
the fluid completely. Fresh fluid is then drawn into the ABS unit, and
the old stuff can be flushed away with the rest of the mess.
The
end result takes a little more time than normal and requires you use a
little more fluid, but looks like this:
Step
1. Manually bleed RR, LR, RF, LF brakes
Step
2. Install service tool and cycle all valves and/or pumps
Step
3. Manually bleed RR, LR, RF, and LF brakes again
You
end up having bled the system twice, but this is necessary to ensure
that fresh fluid - and NOT used fluid - is drawn into the unit the
next time that the ABS valves (and/or pump) are cycled.
But
what if I don’t have the service tool?
If you need
to cycle the valves, but do not have access to a service tool (or if
the retailer is not willing to loan theirs,) you COULD just replace
Step #2 above with "go driving and slam on the brakes a few times
to make the ABS work" to purge the fluid. This is usually NOT the most efficient or socially
responsible solution (though it seems to work just as well). You still need to bleed the car a second time, but it saves
you from procuring the service tool.
But
what about when I’m at the track?
It
should be noted that this is the process for FLUSHING AND FILLING YOUR
ENTIRE SYSTEM. If you are only replacing a caliper or performing any other
operation where you are simply trying to bleed vapor from the
wheel-end components (like after a hard day of lapping,) you need only
to bleed the brakes as you normally would...ala Step #1 above.
There
is no reason to cycle the ABS if all you are simply trying to do is
get vapor out of the calipers. For
this reason, if you flush and fill your system only once per year, the
rest of the time you will not need to perform the ABS cycling
procedure or worry about the service tool at all.
For more
detailed information on how to perform a ‘standard’ brake bleed,
please visit How To Bleed Brakes – the Right Way, also found
in the team scR tech articles section.
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