87 5000TQA Anti-Lock Brake Problem

Bernard Littau bernard.littau at gmail.com
Thu Oct 11 07:55:55 PDT 2007

No, don't just tap them in until they meet the cogs, that's too close and
will likely damage the sensor the first time a spec of dirt gets in there.

The behavior of turning off the ABS (AL) after driving a short bit is
classic bad sensor signal.  The fact that you had a CV replaced means the
sensor was certainly messed with; it's hard to pull the axle out with the
sensor in place.

The wrong number of teeth on the cog is believable.  That would lead the ABS
computer to conclude wheel slip.  I'm surprised the ABS system initialized
with the wheels not matched, but I guess they don't test for that.  ABS is
inactive below a certain speed even if there is wheel slip.

The little plastic cap sits atop the sensor, and you push the sensor +
plastic all the way in until it bumps the teeth.  The plastic has a
sacrificial piece that gets sheared off in use .  This allows the sensor to
be placed at the correct distance and still have an air gap.

The key is correct distance between sensor and teeth.  You can guesstimate
it and nudge the sensor in and out for effect, but that is a lot of work
since you need to drive a bit between adjustments if it's not right.  The
plastic caps are the sure-fire factory-approved one-shot adjustment.


'88 5ktq

On 10/11/07, Ado Sigal <a.sigal at bluewin.ch> wrote:
> Normally after working on axles one must clean the ABS sensor(s), and
> readjust them to correct distance from the toothed wheel. This is done
> by installing new plastic cap on the top, which ensures correct
> distance, but it can be done by simply tapping in the ABS sensor(s)
> until it meets the toothed wheel, then secure the sensor. In most cases
> that is all thats needed.
> Ado
> Stephen Sherman wrote:
> >A bit of a long story, but here goes...
> >
> >The anti-lock (AL) brakes have worked fine on my Avant for 10+ years.
> >Recently I had a shop replace a front axle which had a CV joint that was
> >going out. When I picked the car up, the anti-lock brakes were going
> >crazy. Firing off at slow speed stops even when there was no slippage
> >and at higher speeds (20-30mph) it was downright dangerous. Brought the
> >car back, the shop said they'd look at it and drove it until then with
> >the AL turned off, which I had to manually each time I started the car.
> >>>>
> >>>>
> >No doubt the shop will work on it again, no charge. But I think this may
> >require more knowledge than the guys at this place have. So I wanted to
> >ask the AL gurus here what's up?
> >>>>
> >>>>
> >Can anyone give me a quick tutorial on what kind of problems would cause
> >the AL to turn itself off, and what in an axle change might cause those
> >things.
> >
> >TIA
> >
> >
> >
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