Cycling ABS

[gmcman]

I'm sure there are a few ways to do this, but when I bled my brakes last I wanted to cycle the ABS since this may or may not release any trapped air bubbles within the ABS pump but seems that the consensus is when the ABS is applied the brakes sometimes feel "better" or have a harder pedal.

Perform this at your own risk, and be gentle on the drivetrain. The sole purpose is to gently accelerate the tires to a low speed then apply the brakes, don't aggressively rev the engine or try change from forward to reverse or even remove from a forward gear until you are certain all the wheels have stopped rotating.

With all 4 wheels off the ground, I supported the front by the lower control arms, this jack position works best for me, and used a floor jack for the rear diff. A safer alternative is a jack stand under each axle tube but for the sake of this thread I used the floor jack.



With all 4 wheels supported, I lightly clamped the LF brake line...this should give you 1 or 2 stops before the wheel becomes stationary from the trapped fluid. You want the wheel to slow down at a lower rate than the rest, maybe of you clamped it shut it would still work but I didn't try that. Just don't accelerate the wheels with one not moving.

With the trans in park or neutral, engage 4WD, don't place in gear yet and either you or a buddy, rotate one of the front tires until the disconnect engages, should take a half turn or so as the opposite tire will rotate in an opposite direction once engaged.

Place in gear and accelerate gently until 20-30 mph then apply the brakes. After the first stop, the clamped tire may not rotate, if so don't repeat until you release the fluid to avoid the front diff from being worked too hard.

I bled my brakes first, then performed this method, and bled again.

 

[Mooseman]

Your instructions follow the manual's instructions to a T except for how you cycle the ABS. Only thing though is because the one wheel that is clamped would not be cycled because it is not being locked up, maybe it would be worth it to switch to the other wheel after doing it the first time just to be sure it's thorough.

 

[Sparky]

Interesting way of doing it.

Way I always do mine is go out on a wet road and just slam the brakes on to get ABS to fire lol.

 

[gmcman]

Only thing though is because the one wheel that is clamped would not be cycled because it is not being locked up, maybe it would be worth it to switch to the other wheel after doing it the first time just to be sure it's thorough.

That's a good point, definitely worth doing to be sure.

Edited to add: I looked at the file you linked, in regards to steps 5 & 6, I personally don't like to open the bleeder unless the system is under pressure. I have always pumped up the system 4-5 times, held pressure then opened the bleeder, then closed bleeder before the pedal stops.

 

[Mooseman]

That's true. Under pressure, air would be forcefully expelled rather than just slowly pushed. That's how I like it too.

 

[mrrsm]

Very Nice Write-Up!

My God!... Man... Where in the World did you find those “Jack-Stands-on-Steroids”...? Thanks for posting those images using the Vise Grips. I will have to use a similar method soon. FWIW... it reminded me that buried in one of my Tool Boxes was this weird little H-F $20.00 Set of Hose Line-Clamps that I've never used for anything before...and it looks like the smallest of these might "put the squeeze" well enough on my brake lines to keep the Master Cylinder from Draining Dry when I do the BIG SWAP on the Z-28 soon. What is really cool about these is that if you look close at the area behind the hinge...you can see where they put 2 small "Stops" so that the hose does not get crushed with too much clamping force... a nice feature, too.

Its been so long since I got this Three Clamp Set.. that the color “Black” has apparently gone out of style:

http://www.harborfreight.com/3-piece-line-clamp-set-97578.html

 

[gmcman]

Very Nice Write-Up!

My God!... Man... Where in the World did you find those “Jack-Stands-on-Steroids”...?

Thanks.

Lol....I looked at the pics again and see what you mean...I want to say it was the close proximity of my cell phone slightly distorting the size of the stand base. They are a little smaller they appear.

 

[mrrsm]

Damn...I was hoping to get a set just like those!... This image Kills Two Birds With One Stone... The "distorted" mirror reflection of the T-REX is the EXACT inversion of what your cell-phone must be doing...and as a funny bonus...this Badass Therapod is the exact same color as those "Meaty-Feety" Jack Stands! I was gonna Nick-Name them... "The T-Rex Stands". LOL

"Must Go FASTER!"

 

[gmcman]

The stands used to be black with yellow cradles but they doubled as adjustable painting stands for when my son and I restored a John Deere garden tractor so they inherited that fine green and yellow shade....