Vibration through brake pedal

Ped23

Registered

Would appreciate some help on this.

This problem has been getting steadily worse. I am getting a knocking/vibration through the brake pedal at the last stage of braking — i.e. it does not happen when braking at speed only at low speed or when I am coming to a halt after slowing down over a longer distance.

When it first starting happening in November it did feel that the ABS seemed to be kicking in when it was unnessesary. I went away for a few months over the winter and now I am back driving my van I can really notice it.

The brakes were obviously a bit stuck when I got back and I was careful for the first few days to get the discs clean but this was definitely happening before I went away.

I have an old thread which suggests either a warped disc or a problem with the ABS.

Anyone else had a similar problem or any other suggestions what the issue might be?

Is the ABS easy to check without booking it into a garage?

pedalman

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Ped23

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Ive checked all four discs and they all seem to have smooth wear on them with no grooves or lines.

How can I tell if one of them is warped?

pedalman

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yiman

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Village

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joseff

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Ped23

Registered

Thought it was ABS to start with but now not so sure. Happens fairly sporadically but usually only at very low speed, say 5 — 10 mph.

Feels like a definite knocking through brake pedal not like the judder of ABS.

Good idea about the codes though, plenty needs doing on the wagon so might as well.

JonCa

Registered

Discs if worn badly may cause judder, so are they too thin?

Some brake pads can leave a build-up on the disc surface causing judder, are the discs clean (on both sides)?

Warped, get access to the disc and check for run out. Not the best way (but it works) with the disc turning (engine ticking over in first gear) use a guide held still and very close to the disc surface; while the disc rotates look at the gap between your guide and the disc, it should remain the same size.

pedalman

Registered

bodfish

Registered

As others have said, warped or irregularly worn discs will cause vibration on braking — but this would usually be more noticable when braking at speed, and would tend to be felt through the steering as well as the brake pedal.

The slow speed judder / knock you describe sounds very similar to the fault my 02 Velle has. The ABS taps in a few times occasionally when braking below about 20mph — felt as a knocking through the pedal. The cause of this is a cracked reluctor ring on the driveshaft which causes the ABS wheel sensor to return a false signal, so activating the ABS system. I can see the crack in the ring on mine, just inboard of the hub housing. Replacing the ring is on the list of ‘front end jobs’ for a weekend sometime soon.

If your’re not sure what the ABS operation feels / sounds like just try an emergency stop on a loose / gravel road. This should help you to identify the nature of your problem.