Brake pedal pulsation, not warped rotors.

[Az.Nick]

Hello,

Have an 2003 Jetta ALH, standard, 200K, that had a bad left front abs sensor wire & abs dash light on. Before the sensor was replaced It then started to develop a low speed pulsation in the brake pedal at final stop, while driving straight & turning at low speed only. I thought it was related to the ABS sensor, but it still remains after the sensor was replaced and the abs light is no longer on. It does have an a feeling that that the abs is kicking when the pulsation occurs, like the abs senses a braking issue. Is there some other ABS issue that may persists, due to the abs system not being reset or procedure performed, that I might of missed? Or can this be related to a bad lower control arm bushings possibly, causing the pedal to pulsate up and down due to the LCA moving out of spec? Just want to be clear its NOT warped rotors or in the steering, that is all good and been checked. Thanks in advance.

 

[csstevej]

Have you checked the LCA aft bushings yet?
Jack up the car and grab the control arm and move it fore and aft , is there movement? Are they broken ? I had that issue on my daughters car.
You can always pull the ABS circuit breaker and drive it to see if the pulsing stops, at least rule it out , but I suspect its the LCA bushing. Just my .02

 

[03TDICommuter]

How was the rotor checked?

 

[cjolson140]

I had the same problem with my ALH Jetta, and it was indeed the ABS activating in error. In my case, the ABS controller itself was gradually failing internally and having intermittent faults in the wheel speed sensor circuits. Eventually it progressed to not having any wheel speed reading from 3 out of 4 wheels, and the ABS is now inoperative. Other causes of the low-speed ABS cut in problem seem to be improper wheel speed sensor clearance to the tone ring, bad wheel bearings, dirty/rust covered sensors, bad/dirty connections or even a break in the harness. I’ve read that it’s worthwhile to also check the body grounds under the battery tray.

If you have VCDS you can graph the wheel speed sensors and see which one is dropping out as you’re driving (to the ABS controller it looks like you’re locking up a wheel while braking and that’s why it behaves the way it does)

 

[Az.Nick]

How was the rotor checked?

I had a previous rotor/steering vibration due to warpage and had them turned along with new pads. Seems to be 2 separate issues unless I'm missing something.

 

[Az.Nick]

Have you checked the LCA aft bushings yet?
Jack up the car and grab the control arm and move it fore and aft , is there movement? Are they broken ? I had that issue on my daughters car.
You can always pull the ABS circuit breaker and drive it to see if the pulsing stops, at least rule it out , but I suspect its the LCA bushing. Just my .02

I will get it in the air tomorrow and check for any movement. Did yours pulsate due to

I had the same problem with my ALH Jetta, and it was indeed the ABS activating in error. In my case, the ABS controller itself was gradually failing internally and having intermittent faults in the wheel speed sensor circuits. Eventually it progressed to not having any wheel speed reading from 3 out of 4 wheels, and the ABS is now inoperative. Other causes of the low-speed ABS cut in problem seem to be improper wheel speed sensor clearance to the tone ring, bad wheel bearings, dirty/rust covered sensors, bad/dirty connections or even a break in the harness. I’ve read that it’s worthwhile to also check the body grounds under the battery tray.

If you have VCDS you can graph the wheel speed sensors and see which one is dropping out as you’re driving (to the ABS controller it looks like you’re locking up a wheel while braking and that’s why it behaves the way it does)

 

[Az.Nick]

Not sure what happened with the previous message but here is the rest of it;


csstevej said:
Have you checked the LCA aft bushings yet?
Jack up the car and grab the control arm and move it fore and aft , is there movement? Are they broken ? I had that issue on my daughters car.
You can always pull the ABS circuit breaker and drive it to see if the pulsing stops, at least rule it out , but I suspect its the LCA bushing. Just my .02


I will get it in the air tomorrow and check for any movement. What was your findings, did yours pulsate due to bushings or abs issues?

 

[Mongler98]

top 5 things i have found that cause this issue in order of how often i have repaired / diagnosed it on my or other customers cars.
#1 Warped/ old brake rotors or drums (you said that was not it so lets move on)
#2 Worn or bad outer tie rod or rods (some time inners)
#3 Worn or lost lower control arm bushings
#4 Dirt/ rust between the wheels face and the rotor or drum and some times even rust build up between hub and rotor/drum
#5 failing lug nuts/ studs (racing i have found that supper heat from the pads have melted the powdercoat enough to loosen the nuts/ studs and i have more often found that someone losses one and uses a replacement that does not fit correctly and OR an after market wheel was installed with OEM or some rando nuts/ studs that are not the same pitch or shape but look similar.

 

[Az.Nick]

I had the same problem with my ALH Jetta, and it was indeed the ABS activating in error. In my case, the ABS controller itself was gradually failing internally and having intermittent faults in the wheel speed sensor circuits. Eventually it progressed to not having any wheel speed reading from 3 out of 4 wheels, and the ABS is now inoperative. Other causes of the low-speed ABS cut in problem seem to be improper wheel speed sensor clearance to the tone ring, bad wheel bearings, dirty/rust covered sensors, bad/dirty connections or even a break in the harness. I’ve read that it’s worthwhile to also check the body grounds under the battery tray.

If you have VCDS you can graph the wheel speed sensors and see which one is dropping out as you’re driving (to the ABS controller it looks like you’re locking up a wheel while braking and that’s why it behaves the way it does)

Installed new wheel bearings 8 moths ago;
Will check the connections for rust & harness conditions as well. what should be the proper wheel speed sensor clearance to the tone ring?

 

[Az.Nick]

top 5 things i have found that cause this issue in order of how often i have repaired / diagnosed it on my or other customers cars.
#1 Warped/ old brake rotors or drums (you said that was not it so lets move on)
#2 Worn or bad outer tie rod or rods (some time inners)
#3 Worn or lost lower control arm bushings
#4 Dirt/ rust between the wheels face and the rotor or drum and some times even rust build up between hub and rotor/drum
#5 failing lug nuts/ studs (racing i have found that supper heat from the pads have melted the powdercoat enough to loosen the nuts/ studs and i have more often found that someone losses one and uses a replacement that does not fit correctly and OR an after market wheel was installed with OEM or some rando nuts/ studs that are not the same pitch or shape but look similar.

Thanks, I will inspect for the items you listed.
In your repairs have you ever had the LCA bushings #3 trigger the abs or make the pedal pulsate?

 

[Mongler98]

seeing as it would be impossible for anything other than a severely worn hub bearing or some other farcical exotic failure to interfere with the ABS ring... NO it would not effect the ABS but that does not mean it can't pulse the pedal and or steering wheel. Yes i have had all 5 of them happen to me personally and others cars and they all pulse the brake a little. some more. some less.

 

[Tdijarhead]

A couple of years ago a vendor had a fabulous deal on OEM front brake pads. I bought two sets and put them on my shelf. A year ago I needed front pads on my golf so I bought a new set of Fremax rotors from idparts and pulled those oem pads off the shelf. From almost day one I had a slight vibration when applying the brakes and my front rims became increasingly filthy. I bedded those pads in two or three times, that would help briefly and then back to vibration/pulsation when applying the brakes. I put up with this for about 10k miles till I couldn’t stand it anymore.

I finally ordered a set of akebono pads and pulled the oem ones. My pulsation/vibration dissappeared along with all the filthy dust.

 

[Az.Nick]

A couple of years ago a vendor had a fabulous deal on OEM front brake pads. I bought two sets and put them on my shelf. A year ago I needed front pads on my golf so I bought a new set of Fremax rotors from idparts and pulled those oem pads off the shelf. From almost day one I had a slight vibration when applying the brakes and my front rims became increasingly filthy. I bedded those pads in two or three times, that would help briefly and then back to vibration/pulsation when applying the brakes. I put up with this for about 10k miles till I couldn’t stand it anymore.

I finally ordered a set of akebono pads and pulled the oem ones. My pulsation/vibration dissappeared along with all the filthy dust.

 

[Az.Nick]

Gents,

So I checked out the car this a.m. and after inspection I did notice worn LCA bushings in the rear, which I ordered the kit.
While road testing the wifes car again, I noticed the following;
When braking for a stop I have normal pedal no issues, when at 5 mph or less the pedal will get spongy and go down an 1" or so followed by a sound from the pedal/firewall (sound description is like moving a vehicle with the park brake applied) then a pulsation in the left front wheel, then the pedal will come back to finalize the stop.
kinda sounds like what CJ140 described with the ABS controller, checked the grounds all is clean, I don't have a VCDS to confirm, any more suggestions guys, given the new details?