Bleeding ABS ???

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I found this 2010 thread regarding bleeding brakes systems with ABS: https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2012292

That thread stated that you don't need to bleed the ABS system unless you worked on it, and to simply bleed the base brake system normally. Some people said that the ABS system fluid will mingle with the new fluid eventually. Some recommended activating the ABS system numerous times with a test drive, then re-bleed the base system again.

Is this still the recommended procedures? Any other advice??

Thanks!
 
At least in most GMs all brake fluid flows thru the ABS pump, the big issue is to never let air or fluid with bubbles
get into the ABS, since a special scanner is needed to open all valves and allow air to bleed out.

Bleed as you normally do, if an issue for you, bleed more often, I do it every 2 yrs, also keeps bleed
screws on calipers from seizing! As always suck out the reservoir and put in fresh fluid before you start.
 
This is a Chrysler system similar to my 2010 link above. The service manual has separate bleed procedures for the base system and ABS system. The procedure is bleed base system, bleed ABS system, then re-bleed the base system.

I don't know if this system is similar to the GM you describe. I want to find out if the ABS bleed is even necessary. According to my link, it seems not. Just checking. Thank you.
 
The one time I had to open an ABS component, I used a pressure bleeder and all worked fine.

But newer systems, especially with traction and stability control, are much more complex so the FSM should definitely be checked.
 
The ABS system in my old Civic wagon is in my right foot. I recently replaced the master cylinder after 30 some years and still have the original calipers and wheel cylinders. Exchanging fluid and bleeding the system every couple of years is becoming more important than ever with all the new "stuff" in a modern brake system. It's important to check the instructions and get help if needed.
 
I have seen people try to use the brake pedal and bleed brakes with ABS systems only to have the dashboard light up like Star Wars.

I've always used a vacuum bleeder and bleed through the ABS systems. I've done it this way on at least a few dozen vehicles with success.
 
Man everyone is making this so complicated. Just bleed like you have for years and years. The normal state of ABS valves is wide open. They only cycle when lock up is detected.

That being said, there are a few years of Ford Fusions / Milans that had an issue with air somehow getting trapped in the ABS valve block after a panic stop in which the ABS kicked in. Those can only be fixed by running the scan tool bleed procedure.
 
Originally Posted By: 14Accent
Man everyone is making this so complicated. Just bleed like you have for years and years. The normal state of ABS valves is wide open. They only cycle when lock up is detected.

That being said, there are a few years of Ford Fusions / Milans that had an issue with air somehow getting trapped in the ABS valve block after a panic stop in which the ABS kicked in. Those can only be fixed by running the scan tool bleed procedure.


Don't think that is 100% accurate. I have a 2003 F-150 that I let the reservoir run dry while bleeding the brakes. Pedal acted funky for years and only acted normal when the ABS light came on in really cold weather. Took it to the mechanic last year and had him cycle the ABS. Been fine ever since.
 
I ended up doing a standard base brake bleed/flush yesterday following new shoes on the back.

Two odd things happened. I started out trying to do a pressure bleed and it didn't seem to work. This happened on my last Caravan also. Pressurizing the reservoir did not push fluid out the bleeders. I ended up doing a manual brake pedal flush. The second oddity is that I began by replacing the old fluid in the reservoir before bleeding the 4 corners. At the end of the entire procedure, there was a layer of discolored fluid in the reservoir, as if it was floating above the new fluid. I sucked out the reservoir, refilled with new fluid and called it done.

Thanks for the comments.
 
Some cars need OEM-level or capable aftermarket scan tools to home the ABS modulator valves or to cycle the solenoids/disable braking control to allow the system to be bled. Delco and Kelsey-Hayes systems as well as any Toyota hybrid should be bled that way.

I recently replaced the master cylinder on a friend's Chevy Tahoe. I didn't have access to a GM Tech II/Vetronix MasterTech and I didn't want to bug someone with a Snap-On Scanner. What we did was bleed the brakes until the pedal was firm and we drove to a open lot. We did quite a few panic stops to cycle the ABS and drove back home carefully to rebleed the brakes.
 
Originally Posted By: doitmyself
This is a Chrysler system similar to my 2010 link above. The service manual has separate bleed procedures for the base system and ABS system. The procedure is bleed base system, bleed ABS system, then re-bleed the base system.

I don't know if this system is similar to the GM you describe. I want to find out if the ABS bleed is even necessary. According to my link, it seems not. Just checking. Thank you.



If there's separate bleed procedures, you may have to do it, brake fluid in the ABS deteriorates just like anywhere else in the system,
jammed valves in an ABS would be a big problem and big $$.

After doing brake jobs in cars with 10 yr old plus brake fluid and the damage inside, I bleed the heck out the family cars
to avoid major repairs!
 
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