mk1 ABS "dancing"

[Mile30]

The car has "up" for the winter pretty much, and as the weather has finally started to get more amenable I'm taking local trips with it again (as opposed to running it an hour or two a week all winter)...

I started noticing a few days ago that the ABS was kicking in and "dancing" under my foot as I approach a stop or turn. Which is really wierd because when I try to duplicate the behavior after the light turns green/after the stop or turn; the pedal will not do it! It was a curious thing three days ago. When I took it around the way a day later I noticed the behavior only when speed dropped near a turn or stop. As if the car knew where it was! On the way back from a family dinner, it starts doing it again, so I lament it to my gf as the damn ABS light comes on near the house.



I had just stopped to sate a hunch that the psi was low (everything was 15lbs low), so after pumping all four back up I figured it was licked... has anyone had this happen? Anyone have another idea?! I'll be doing more diag tomorrow with the sun out; I'm just fishing for a few ideas as to where to start looking!

[Sponsor]

[Mile30]

Eff, grammatical errors...

[02fordsvt]

It's hard to tell through a description when I'm not in the car but it sounds like the ABS is doing what it supposed too. Are you under heavy braking when the peddle starts pulsing? If so, it means the your wheels have locked up and the ABS is trying to maintain the traction of the front wheels. It's very easy to lock the front wheels up this time of year do to all the sand on the roads so you may be locking the wheels up a lot more that during the summer months.

[Mile30]

No no; this isn't a question of basic ABS operation... rather a peculiar and new "behavior" that occurs when approaching a stop sign or light. I thought it was related to the typically choppy pavement you usually see at main intersections. Then it became evident when slowing to take turns. Not during emergency or hard braking, that doesn't feel abnormal save for the fact that I seem to remember braking being sooner when the car was newer! The pedal "kickback" is very slight. I barely noticed, except I heard it a few mornings ago and then noticed a slight feeling under my work boot.

The pads and rotors are all in great shape (replaced 6 months ago and parked for the winter), so I'm gobsmacked as to what the deal could be! I'm runnin g around looting for work and taking care of chore s on my day off now; I'll be crawling around the damn thing here in an hour or two to do a visual inspection.

Here's what I've been able to see thus far:
-no leaking under the car
-fluid is at appropriate level
-brake fluid is slightly dark

[Mile30]

Ran "Test Mode" earlier... nuthin'!

YouTube Video

Good Info here:
http://www.focusfanatics.com/forum/showthread.php?t=2641
And Here:
http://www.focushacks.com/mod/Instru...ster_Test_Mode


I tried taking a peek around the brake rotors to see if one of the speed sensors had possibly gone awry... the car's pretty damn low, so I couldn't see a damn thing. They looked to be going in where they should, but I'm gonna have to throw it up in the err for a proper look. Cross my fingers that continued driving is just a matter of slowing down early enough that I won't need the ABS...

I hope it's maybe just a loose connection on the back of the traction control button,or something stupid/simple like that!

[Mile30]

A bad wheel bearing. That was the correct answer!

The fault is coming from improper air gap or contact between the sensor and tone wheel... soooo this is gonna be A LOT of fun. The tech that helped me recommended just getting a new knuckle and carefully pressing in a new bearing; and then installing a new wheel speed sensor. Easy as pie

[02fordsvt]

Wouldn't have guessed that; glad you found it, though.

[Mile30]

Originally Posted by 02fordsvt

Wouldn't have guessed that; glad you found it, though.

I didn't either! I dismounted the wheels 3 times (and bled the brakes) and never noticed the excess end play (reeeeeeally obvious once the IDS confirmed/pointed to the right-front and elicited more attention to the condition of everything)... once we watched the scope drop the signal up there, we looked more carefully!

[Mile30]

I saw a flyer on the parts-desk at work for a "free lunch" for local techs at the nearest NAPA auto parts, so me being thrifty; I headed down to investigate. They had an SKF Bearings truck/display and representative there to give the folks that showed up a little rundown on his stuff.

Turns out SKF is the company that supplies FMC with the stock bearings in the majority of their line-up; and a large number of other major manufacturer's use their stuff too! Imagine my surprise, as I'm trying to get my car worked out...



So with my need for a new bearing and sensor, I enjoyed a lil bit 'o' bbq while the gents from SKF went through their pitch: and I recognized one of the items in their display



I got ten hard-ass years worth of driving on these bearings before one decided to crap the bed on me, and with FR13 closing in real fast now; this was a Godsend! A little bit more info to bolster my confidence and tips on why this bearing going bad could be contributing to such mushy pedal-feel.

I'll put any work-pics on here as I get my ess-eych together and tear the knuckle and bearing from the car!

[03FocusZX3]

Glad you figured out what was wrong :) I recently had the same symptoms you had, was a wheel bearing here also :P