ABS/Brakes Malfunctioning? - JeepForum.com
 
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post #1 of 4 Old 11-16-2019, 11:22 AM Thread Starter
dj_hp
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2008 WK 
 
Join Date: Nov 2019
Location: Toronto
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ABS/Brakes Malfunctioning?

**SEMI LONG POST AHEAD**

Hey everyone, so I recently purchased an '08 Grand Cherokee CRD and have a question regarding how our ABS function. Recently we had a huge snowfall and decided I'd try how the GC fares up in terms of handling and stopping. I got ABS to kick in the snow a few times. It was normal at first where the usual juddering/pulsating happens with the brake pedal. THEN I decided to fully SLAM on the brakes to see how the ABS responses. This is where it scared me.

It fully locked the brake pedal down even after I took my foot off, and I was trying to give it some throttle so I could countersteer, but nothing was happening (no power, couldn't rev up). Basically, I lost complete control over brakes and throttle until the truck was fully stopped, then I was able to give it throttle again. I thought maybe the low brake fluid level could be messing up with the ABS (since I needed to change my front pads/rotors).

Fast forward to yesterday, I changed my pads/rotors. In the process of breaking in the coated rotors (50 km/h - 5 km/h braking few times), I braked a little too hard on the last run. ABS kicked in, and it did exactly the same thing - fully locked my tires to the ground, no control of brakes/throttle. It didn't even sound like ABS was functioning right cause I was screeching for at least 50 feet. I know this exact screeching sound, it was like if you fully lock the wheels on a non-ABS equipped car.

So, anyone have an idea of what's going on here? I have absolutely no codes. Even scanned it with BlueDriver to see if I have pending codes. Nothing.

(Sidenote: I think with the tires getting locked up combined with the soft compound of winter tires, it created flat spots on my tires. A pulsating feeling has now appeared and it goes with vehicle speed. I know I did not warp the rotors as braking normally feels perfectly fine)

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post #2 of 4 Old 11-17-2019, 05:53 AM
Avs
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Quote:
Originally Posted by dj_hp View Post



(Sidenote: I think with the tires getting locked up combined with the soft compound of winter tires, it created flat spots on my tires. A pulsating feeling has now appeared and it goes with vehicle speed. I know I did not warp the rotors as braking normally feels perfectly fine)

I would go back and double check and see if you install the brake correctly. Did you lightly sand/wire brush the wheel hub prior to installation of new rotor? What about runout check of the rotor surface? An unevenness between of rotor and hub mating surface can cause the brake to pulse when you brake at higher speed. How’s the brake fluid condition? Did you bleed the brake? You can also bleed the abs pump with an obd2 scanner with bidirectional capability.
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post #3 of 4 Old 11-17-2019, 09:40 AM Thread Starter
dj_hp
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2008 WK 
 
Join Date: Nov 2019
Location: Toronto
Posts: 7
Quote:
Originally Posted by Avs View Post
I would go back and double check and see if you install the brake correctly. Did you lightly sand/wire brush the wheel hub prior to installation of new rotor? What about runout check of the rotor surface? An unevenness between of rotor and hub mating surface can cause the brake to pulse when you brake at higher speed. How’s the brake fluid condition? Did you bleed the brake? You can also bleed the abs pump with an obd2 scanner with bidirectional capability.
Yep everything was done correctly (slide brackets lubed, hubs wire brushed, caliper pins wire brushed and lubed, etc.). It was done at a shop. Also, it does not pulse when braking. It pulses as the vehicle rolls and it goes higher with the vehicle speed. So I'm almost 100% sure it's not the brakes causing the pulsation. Brakes were not bled as we did not open the bleeders. It was just a straight front pads/rotors replacement.

The thing that really concerns me is the fact that when ABS is fully activated, it locks all my wheels up instead of doing what it's supposed to do - NOT lock the wheels lol

Last edited by dj_hp; 11-17-2019 at 09:42 AM. Reason: More info
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post #4 of 4 Old 11-17-2019, 10:23 AM
SteveROntario
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Join Date: Sep 2017
Location: Ottawa Valley
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I had this happen as well, I ended up changing the master cylinder and booster. I could hear a sucking sound coming from the booster behind the dash board. You should be able to pull the pedal back up when driving to correct it, that is what I did on the short term. Expect to buy a few new calipers when you go to bleed things as the bleeders are designed to brake off... I had to go back in a few days later and change the stop lamp switch too, they don't like being removed and reset.

2013 Civic, 2009 Suzuki DRZ-400SM, 2008.5 Grand Cherokee CRD, 1991 Dodge B250, 1934 Hupmobile 417W
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