DIY ABS Flush '03 Sierra

[stevewaclo]

Hello,

 

The 2500 HD I recently purchased is due for a brake flush and I believe I can do it myself. My concern is removing old fluid from the Kelsey-Hayes 325 ABS unit, without benefit of a shop scanner. My research indicates a routine flush will leave dirty fluid in the ABS, but if I do a standard flush, then exercise the ABS several times on a low friction surface, activation of the system will pump clean fluid through the ABS. A second flush will then be necessary to remove that fluid.

 

Also, I've read the amount of dirty fluid expelled from ABS during an on road cycle is minimal and some folks just do a flush, cycle the ABS on a gravel road and not worry about the small amount of fluid that mixes with the clean fluid.

 

Also, it occurs to me that since the ABS system does a self-test at every start-up, how many times would I need to cycle through self-test to move all of the dirty fluid out into the system? I could then follow up with another flush, or not (see above).

 

Thanks for your advice.

 

Best wishes.

[stevewaclo]

Hello all,

 

Finally had to take keyboard in hand, contact two highly regarded sources and get my own answers.

 

Here is part of an email I wrote to one source:

 

"ABS pump hydraulics-brake fluid content"

 

Been doing quite a bit of searching for the numbers you provided. According to my RN wife, 20cc would only be about 2 tablespoons of fluid. And as you pointed out, comparing that amount (in the ABS hydraulic system) to the total in the system, makes it insignificant. 

 

Just got off the phone a few minutes ago with John at Reman Inc., an international rebuilder of ABS pumps, among other hardware. Just wanted another source :-). At the end of our conversation, I asked John to run through his credentials and his are almost as impressive as yours! Anyway, he confirmed your estimate of 10-20 cc of fluid in the ABS hydraulic circuit is accurate, and considering the total amount in the system, is not enough to be concerned about. He also pointed out that for those of us who are worried about such things (ahem), 3-4 stops on gravel, followed by another complete flush, would assure removal of even that small amount of fluid from the system.

 

Regarding my question about the system self-test, that as you know, occurs at about 5-10 mph on every trip, the amount of fluid that cycles through the ABS pump is absolutely minimal. What that says to me is if one is truly concerned about that trapped fluid, occasionally exercising the system, beyond the automatic self-test, would be a good thing. 

 

 

These answers, from two pros, answered my questions and I plan to do a regular flush, followed by a few ABS stops.

 

Best wishes.