Bleeding ABS brakes

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Bleeding Saturn Anti-Lock Brakes
…is it really as difficult as it sounds?

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.