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Noise while hitting the brake when near a stop.

Tiny
CHANGCHINGCHI
  • MEMBER
  • 2004 VOLKSWAGEN PASSAT
  • 92,000 MILES
Hi, guys,

I just got another problem after I installed the new upper control arms and CV axles for both sides. I just made a video in order to describe this symptom more clearly. the mechanic told me that is because of the brake pad are new. However, this never happened before I installed the new parts on it.( I already have the brake pad for a while). please help me figure this out.....I will be so appreciated.

this happened only when I "ALMOST STOP" and pressing the brake.my foot can feel something when put it on the brake pedal, its like I'm against something..

the only thing they did to my car is..I think we did the tire rotation, new cv axles, new upper control arms (bushings). I think thats all. I am just afraid that I am destroying something which I don't know.......if I leave the problem there.

please see the video and hear the noise. the noise comes when I hit the brake

http://www.youtube.com/watch?v=lHXo_t1tiog
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Sunday, October 7th, 2012 AT 10:55 PM

18 Replies

Tiny
EXOVCDS
  • MECHANIC
  • 1,883 POSTS
Do you feel vibration in the brake pedal? If yes, the it is you abs that is kicking in at lower speeds.

Check the front abs speeds sensors to see if they are sitting all the way in place. An air gap
that is bigger for one sensor than the other will cause different speed readings by the abs
module and activate the abs.

Thomas
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Sunday, October 7th, 2012 AT 11:26 PM
Tiny
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Stupid spell check. "Then it is your abs that is kicking in".

I just re-read your post. You are feeling something in the pedal, so I would for sure check the front
abs sensor positions.

Thomas
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Sunday, October 7th, 2012 AT 11:29 PM
Tiny
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If the gaps are OK. Check the teeth of the outer cv joints. Chipped, broken or cracked teeth will
cause signal issues that can cause abs activation.

Thomas
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Sunday, October 7th, 2012 AT 11:36 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Also check for rust as that can cause noise problems.
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Sunday, October 7th, 2012 AT 11:48 PM
Tiny
CHANGCHINGCHI
  • MEMBER
  • 13 POSTS
Can it be the problem from caliper?
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Monday, October 8th, 2012 AT 3:09 AM
Tiny
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Not if what you feel in the pedal is a rapid pulse.

The noise I am hearing is the ABS pump & valves clicking. But I can't
be 100% sure unless I feel & hear it in person.

The fact that all this started AFTER you had the CV / drive shafts
replaced, leads me to think that there is an ABS issue (sensor or
tone wheel on the outer cv joint).

A loose caliper bolt can cause a 1 time knock during brake application
that can be repeated less rapidly.

Thomas
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Monday, October 8th, 2012 AT 3:19 AM
Tiny
CHANGCHINGCHI
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  • 13 POSTS
I will just ask them to check from what you said. From ABS pump & valves, the front abs sensor, to the teeth of the outer cv joints. Will updated it.
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Monday, October 8th, 2012 AT 4:00 AM
Tiny
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Some reading before you take it in....

http://www.picoauto.com/tutorials/diagnosing-abs.html

Thomas
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Monday, October 8th, 2012 AT 6:16 AM
Tiny
CHANGCHINGCHI
  • MEMBER
  • 13 POSTS
Hi, Thomas.

They are doing the reface the rear rotor and checking the abs sensor this time. But, something suddenly come to my mind, do you think it is possible because of wrong size of the CV axles? ( Can install but have space?) Furthermore, if it is because of the abs sensor, you think that can be better if we reboot the system?( Disconnect the battery?)
thanks for your helps. :)
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Monday, October 8th, 2012 AT 8:52 PM
Tiny
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Depending on make / manufacturer of the shafts and as long as the
shop ordered the correct parts, I don't think that the "wrong"
shafts were installed. I would think that there would be a hard
fault at that point (ABS light ON & a stored fault code present in
the ABS Module) with an incorrect shaft installed.

Have them double check the parts to be sure.

A re-boot / disconnect probably won't fix anything.

On one of the other forums that I post on, someone changed his
cv shafts as well and had the same problem after. In his case
he noticed that one of the front sensors was not sitting all the
way in its seat. He lightly tapped it with a rubber hammer and
his low speed abs activation stopped.

Not sure why they are now focusing on your rear brakes. Like
you said, the problem was not present before the front cv shaft
change, so I would keep focus on the front.

Also, CV shafts can be changed without having to remove brake calipers
and pads. Ruling out any fault with those components.

Thomas
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Monday, October 8th, 2012 AT 9:07 PM
Tiny
CHANGCHINGCHI
  • MEMBER
  • 13 POSTS
Hi, Thomas,

I ask them to remove and install again about the ABS sensors and also they did the reface for all rotors. Problems seems getting better, but the noise still there. They ask me to go there and have a computer-scanned. Will keep updating. Thanks for your helps.
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Tuesday, October 9th, 2012 AT 2:23 AM
Tiny
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Thanks for the update!

Did they at least verify that my "guess" was correct? The noise
that you are hearing / feeling is the ABS activation?

The scan might not show a fault code. Remember, the ABS system is
triggered because the ABS Module "thinks" that one of the wheels
has stopped turning and because of that, it releases & applies
brake pressure rapidly and does not store a code because of that.

Thomas
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Tuesday, October 9th, 2012 AT 2:33 AM
Tiny
CHANGCHINGCHI
  • MEMBER
  • 13 POSTS
I haven't taken a longer test drive. At least, it doesnt happen in 5 miles on the way to school. When they took a test drive, hit the brake very strongly and the noise came. (But when I hit it very slow, there was no noise for that moment). One of the mechanic said that is normal for some types of vehicle. Seems that now the problem only exist when hitting the brake very strongly and suddenly. Ps. I guess that it is just about the abs system. But they told me the abs system looks pretty normal, nothing wrong when they checked it. Forgive my bad english.
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Tuesday, October 9th, 2012 AT 2:41 AM
Tiny
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Your English is fine, I'm German. I had to learn as well! :-)

ABS activation when pressing hard (on dry flat roads) is normal.
ABS activation when pressing soft (on gravel, wet / snow roads) is normal.
ABS activation when pressing soft (on dry flat roads) is not normal.

I can drive my car for several weeks and never feel the ABS. It
all depends on the road conditions.

If it continues to happen, especially on dry flat surfaces & at
low speeds, then something is still wrong.

Continue to monitor it and see what happens.

Good luck,

Thomas
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Tuesday, October 9th, 2012 AT 2:54 AM
Tiny
HMAC300
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One thing here is you said that they heard the noise with a strong application, that may be just he abs unit making the noise due to the application. Alot of gm cars make a whine/groan type of noise and it's only normal because it's the abs unit working.
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Tuesday, October 9th, 2012 AT 1:43 PM
Tiny
CHANGCHINGCHI
  • MEMBER
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Ok. Thanks, but one thing I'm thinking is shouldn't it be quiet when abs is working? And feel nothing on ur feet? Which mean even the abs is working but we shouldn't feel it? I probably make another video and let you guys see.
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Tuesday, October 9th, 2012 AT 3:03 PM
Tiny
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As long as the ABS light in the dash is OFF while driving, the system is ON.

Once the ABS is Activated, you feel & hear the abs pump.

During normal daily driving, you should not hear / feel the ABS, simply
because it is not needed.

If the ABS light is always ON, then the ABS is Deactivated because a
fault is detected in the system.

Thomas
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Tuesday, October 9th, 2012 AT 5:10 PM
Tiny
CHANGCHINGCHI
  • MEMBER
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Hey, guys.

For this moment, I think the problems had been solved, at least I never feel anything in normal brake application. It is fine for me. What they did are checked all the abs sensors and reface the "all" rotors". Also, I asked them to disconnect the battery in order to reboot the whole system. I don't know which part worked, at least it is fine right now. Meanwhile, I was told the motor mounts for both sides are bad which make my car has vibration around 60-80 mph( I just finished the tire-balancing). So, I guess that will be my next thing to do.I am planning to change the motor mounts by myself. I searched so info online. I think it wont be that's hard to do, any idea? :)
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Wednesday, October 10th, 2012 AT 5:27 PM

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