Bleeding ABS? - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 21 Old 09-16-2010, 09:48 AM Thread Starter
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Bleeding ABS?

I have a feeling (actually, a SPONGY feeling) that when we swapped out the brake lines last year on my JK we got some air into the ABS system. I've pressure bled the brakes several times using my little Motive Power pressure bleeder and am satisfied the air is all out of them. However, the spongy bullshit still remains. Reason I'm concerned is I've noticed on steep trail grades that I'm mashing the pedal all the way to the stop, and in some cases the JK still wanted to creep backwards. In all other cases the brakes work fine, the ABS does work ok if I make it engage and no ABS or other brake warning lights ever come on.

So, after I decided there may be some air in the ABS I tried to see if I could bleed the ABS system. Unfortunately, the official (POS) factory manual says it has to be done using a scan tool only available to the dealer. I'd hate to have to entrust this procedure to the same dealer tech moneys who left my oil filter loose last time I had them change the oil, so I wonder if anyone has a bleed procedure for the ABS I can do myself. FWIW, I have done the old "gravel road, mash the pedal & engage the ABS, then bleed 'em again" routine and it made no difference.

Thanks in advance for your help!
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post #2 of 21 Old 09-16-2010, 09:54 AM
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My pedal has always been soft it the JK compared to most vehicles. One thing to check is your fitting and bleed ports on the calipers. I had them leaking slightly in the past and it will cause them to suck air when you let off the bake. Make sure you bleed all four or you're wasting your time.

Next step may be a new master cylinder.
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post #3 of 21 Old 09-16-2010, 09:59 AM Thread Starter
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Thanks. Yeah, I pressure bled all four in sequence and the fluid's bubble free. The ABS/BAS is separate and apparently each solenoid has to be bled, then the motor pump unit. I thought there might be a way to trigger them and bleed them at the lines.
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post #4 of 21 Old 09-16-2010, 10:06 AM
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Quote:
Originally Posted by SoK66 View Post
Thanks. Yeah, I pressure bled all four in sequence and the fluid's bubble free. The ABS/BAS is separate and apparently each solenoid has to be bled, then the motor pump unit. I thought there might be a way to trigger them and bleed them at the lines.
Might be, I just am not aware. If there is one, it would be a nice tidbit to know.
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post #5 of 21 Old 09-16-2010, 04:24 PM Thread Starter
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Went by the dealer today to get a sanity check on my pedal feel and sure enough, stocker has a much firmer pedal with far less free play. Made an appointment to have them bleed the ABS, which took me forever to explain to the service advisor. She'd never heard of a "scan tool", or that it had an "ABS bleed routine". Told her I'd print out the procedure from the service manual when I brought it in, she was astonished I had one. Explained to her you could buy one on DVD from Mopar directly off the web: "You CAN???!!! "Why would they do that?"
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post #6 of 21 Old 09-16-2010, 08:06 PM
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You can always go driving and slam the brakes on....or while offroad anything to actually get the ABS to engage. AFter that bleed them one more time and you should be good.....simple
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post #7 of 21 Old 09-16-2010, 08:17 PM Thread Starter
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Thanks. I tried that and it really didn't do anything, not sure it moved any air out of the pump at all. I read that on the JK's ATE system that you'd have to activate the ABS 5-10 times, then bleed them immediately, like on the spot or the air will be drawn back into the pump as you drive back to the shop.

A thought I've had is to pressurize the system with the pressure bleeder, then crack open each of the six lines going into and out of the ABS unit individually. Haven't tried it because I'm not sure there aren't spools in there that might go wacky.

As it is the ABS works fine and no lights have ever come on. I just know from driving other JKs that the pedal feel and reverse loaded braking aren't right.
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post #8 of 21 Old 09-17-2010, 12:16 AM
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Quote:
Originally Posted by SoK66 View Post
Went by the dealer today to get a sanity check on my pedal feel and sure enough, stocker has a much firmer pedal with far less free play. Made an appointment to have them bleed the ABS, which took me forever to explain to the service advisor. She'd never heard of a "scan tool", or that it had an "ABS bleed routine". Told her I'd print out the procedure from the service manual when I brought it in, she was astonished I had one. Explained to her you could buy one on DVD from Mopar directly off the web: "You CAN???!!! "Why would they do that?"
can you post that in this thread?
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post #9 of 21 Old 09-17-2010, 07:19 AM Thread Starter
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Here you go, straight from the JK FSM:


ANTILOCK BRAKE SYSTEM BLEEDING
The base brake's hydraulic system must be bled anytime air enters the hydraulic system. The ABS must always be bled anytime it is suspected that the HCU has ingested air.

Brake systems with ABS must be bled as two independent braking systems. The non-ABS portion of the brake system with ABS is to be bled the same as any non-ABS system.

The ABS portion of the brake system must be bled separately. Use the following procedure to properly bleed the brake hydraulic system including the ABS.

NOTE: During the brake bleeding procedure, be sure the brake fluid level remains close to the FULL level in the master cylinder fluid reservoir. Check the fluid level periodically during the bleeding procedure and add Mopar® DOT 3 brake fluid as required.

BLEEDING
When bleeding the ABS system, the following bleeding sequence must be followed to insure complete and adequate bleeding.

1. Make sure all hydraulic fluid lines are installed and properly torqued.
2. Connect the scan tool to the diagnostics connector. The diagnostic connector is located under the lower steering column cover to the left of the steering column.
3. Using the scan tool, check to make sure the ABM does not have any fault codes stored. If it does, clear them.

WARNING: When bleeding the brake system wear safety glasses. A clear bleed tube (1) must be attached to the bleeder screws and submerged in a clear container filled part way with clean brake fluid (2). Direct the flow of brake fluid away from yourself and the painted surfaces of the vehicle. Brake fluid at high pressure may come out of the bleeder screws when opened.

NOTE: Pressure bleeding is recommended to bleed the base brake system to ensure all air is removed from system. Manual bleeding may also be used, but additional time is needed to remove all air from system.
4. Bleed the base brake system. (Refer to 05 - Brakes - Standard Procedure)
5. Using the scan tool, select ECU VIEW, followed by ABS MISCELLANEOUS FUNCTIONS to access bleeding. Follow the instructions displayed. When finished, disconnect the scan tool and proceed.
6. Bleed the base brake system a second time. Check brake fluid level in the reservoir periodically to prevent emptying, causing air to enter the hydraulic system.
7. Fill the master cylinder fluid reservoir to the FULL level.
8. Test drive the vehicle to be sure the brakes are operating correctly and that the brake pedal does not feel spongy.
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post #10 of 21 Old 09-17-2010, 08:50 AM
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The SM text is very vague when it comes to the Scan Tool / ABS portion of the system! Lots of detail about bleeding the base side of the system. nothing new for most of us. I'd sure like to know exactly what the scan tool is doing on the ABS side.
Thanks for posting it.
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post #11 of 21 Old 09-17-2010, 09:44 AM Thread Starter
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Well, there's a thought here that if I'm not getting an ABS light and if the system works, which it seems to do, that there may just be some air in the master cyl that's not getting burped out when I pressurize bleed the system. I'm going to try a simple bleed under pressure on the two lines at MC & see what happens. Brakes work ok, doesn't pull either side. However, there does seem to be a lack of pressure on the rears which becomes apparent when on the trail and having to stop on a significant incline. Under pressure the system flows very little fluid volume to the rears compared to the front, which may just be by design for proportioning.
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post #12 of 21 Old 09-18-2010, 07:19 AM Thread Starter
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Ok, well, that didn't help at all. Pressurized the system and bled right at the master cylinder hard lines. No improvement noted. I then flushed the system completely, probably ran nearly a gallon of fresh brake fluid through it and nada, no improvement. So, we'll just have to let the dealer try the Starscan ABS bled routine & see what happens.
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post #13 of 21 Old 09-22-2010, 01:33 PM Thread Starter
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Ok, so this AM was the big moment for the JK to get the Starscan ABS bleed routine done by the local Jeep dealer. The guy ran the procedure & claimed all was well:

No improvement!

So, the only thing I can think of is that thew problem is the Poly replacement lines are flexing more than the stockers, hard as that is to believe. WTF?
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post #14 of 21 Old 09-22-2010, 02:29 PM
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If you pump your pedal a few times during braking does it feel more firm?
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post #15 of 21 Old 09-22-2010, 09:12 PM
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I'm gonna bet he says no! 'cause mine sure don't.
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post #16 of 21 Old 09-22-2010, 11:48 PM Thread Starter
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No, they don't pump up. I'm left with chasing the system for something loose or something wacky with the MC or booster setup. I've just R&R'd all 4 calipers when I installed new axle shafts and didn't find anything amiss.
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post #17 of 21 Old 09-23-2010, 08:19 PM Thread Starter
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Ok, so I can't stand this issue any longer and decided to bleed the damn thing one more time. I put the pressure bleeder on it like always and ran the usual routine. Some bubbles came out of the left rear and the right front, thought I was seeing things. Hmmm, the pedal firmed up. I took it up some 10 percent grades, hmmm, good brakes. I wonder, did the friggin' dealer tech bleed the brakes after he ran the Starscan ABS routine? I bet not....

Why would I expect different? This is the same dealer who's tech used to overfill the oil on my Grand Cherokee and left the filter loose on this poor bastard.
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post #18 of 21 Old 09-23-2010, 08:30 PM
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My brakes feel the same way and i bled them. Not sure why but it seems that its a lot harder for me to hold on a hill also, ????

37s on Raceline Beadlocks 5.38 Yukon Gears
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post #19 of 21 Old 09-23-2010, 09:51 PM
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I have one of those pressure bleeders as well and found that having someone pump the brakes worked better.

1) have friend pump pedal a few times till pedal is hard.
2) hold pressue down on last pump up
3) loosen the bleed valve and let the fluid out
4) tighten bleed valve
5) repeat till no bubbles

Im sure you know the process. But thats what worked best for me. Better than the pressure bleeder. Mine felt like it wasnt fitting tight enough on the bleed nipple and was pulling air in. /shrug

Best of luck.
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post #20 of 21 Old 09-23-2010, 11:15 PM Thread Starter
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The pressure bleeder I'm using attaches to the reservoir (in place of the cap) cap and forces fluid through the system. I have a Chrysler specific adapter for it. This is the way factories bleed brakes in production, only at a lot more pressure. I'm going 20lbs max, factory might use 100lbs +. There's a warning right on the reservoir: "Max Fill Pressure 150lbs."
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post #21 of 21 Old 09-23-2010, 11:22 PM
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Quote:
Originally Posted by SoK66 View Post
The pressure bleeder I'm using attaches to the reservoir (in place of the cap) cap and forces fluid through the system. I have a Chrysler specific adapter for it. This is the way factories bleed brakes in production, only at a lot more pressure. I'm going 20lbs max, factory might use 100lbs +. There's a warning right on the reservoir: "Max Fill Pressure 150lbs."
ahh...its a push not a pull. gotcha
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