ACE1252

Has anyone removed the ABS motor pack without first driving the pistons to the bottom of the ABS modulator? Any issues with doing it this way?

I would like to change the motor pack on my ABS modulator, but don't have the tech tool to drive the ABS pistons to the bottom of the ABS modulator.

I suspect I have a motor with a weak brake on it.

ACE1252

I may have an answer to my question.

The pistons are under pressure via the motors. When removing the motor pack without a tech 1 or tech 2 tool, keep your fingers clear of any of the gears. Before installing the new pack, rotate all the modulator gears counterclockwise until they stop. Install the motor pack then reinstall the modulator onto the car attaching all hydraulic lines and electrical connectors.

Before beginning any bleeding procedure, start the car without touching the brake. Allow the car to idle for at least 10 seconds after the ABS light goes out. Repeat. Doing this will cause the ECBM to rehome the pistons in the modulator immediately. This is important to proper bleeding. Otherwise, pressing the brake upon starting will cause the ECBM not to rehome the ABS modulator until the car is moving above 3mph.

There is a note, in the Buick Know How video, that 1996 and above does the re-home at startup whether the brake is pressed or not. However, I think, my 1996 F-body manual makes mention that the re-home will not happen immediately if the brake is pressed....so I'm not sure if the Buick's are just this way or if what was in my 1996 F-body manual was a carry over from the 1995 manual.

At any rate, if the ABS light stays on, something is wrong......and you need to figure out what is the problem.

I'm going to try this in a couple of weeks and will report back on how it goes.

ACE1252

I'm not going to mess with the car til next weekend, but I did pull the pack off the used unit I have. Those things are preloaded around 45* after reaching the top of the bore. The modulator gears spun quite a bit when I pulled the pack off.

Not as big a deal as I thought, but again keep fingers clear of the gears.

ACE1252

I got this done today and it went fairly smooth.

The only thing that got me concerned was when I fired the car up to re-home the modulator pistons. The ABS light stayed on and didn't go out.

So I shut the car down for a few seconds and fired it back up without touching the brake again. This time the ABS light came on for a couple of seconds and went out like normal. You are supposed to leave it running for at least 10 seconds after the ABS light goes out.

I bled the brakes and so far it has helped the braking. I've got a much better feel out of the pedal than with the old motor pack. My stopping force has increased as well. I'd like to grab a brand new motor pack, but for now I'm going to stick with this $25 '97 used one and see how long it lasts.