[bmw] RE: E28 535is ABS Pulsing

["Doug Dykaar" <dykaar@xxxxxxxxxx>]

Georg,

When the sensors get old and rusty, the pickup can be pushed away from the
"gear" on the hub. The "gear" gets filled with crud over time. The net
result is the signal going to the abs computer gets diminished and at slow
enough speeds, the limit for one or more sensors is passed the system
cycles.

Bosch mechanics will have a tool that plugs into the cable and can identify
the low sensor. I got some used front sensors BEFORE I started hacking. One
front was so rusted in place it came out in pieces. I wire brushed the hole
in the hub, and filed down the raised sections on the sensor to tweak the
sensor closer to the hub. I used a tiny dremel ball mill in a cordless hand
drill to clean out each groove in the front "gears".

To get access to the "gear" you need to remove the caliper (don't forget to
make a wire hanger for the caliper to keep from pulling on the brake hose)
and the disc.

I faked the bosch tool with a digital multimeter set to record max AC
voltages, and drove at 10 mph to gauge how much better a particular sensor
had gotten. At this point, I've cleaned the fronts and replaced the front
sensors. I still have the rears to clean and probably have to revisit one of
the fronts.

Its straightforward, but about as tedious as it sounds.

Regards,

-doug
85 e28 535 136Kmi.

Hi BMW digester,

A scan through the local newspaper by my father while on a
visit to Texas lead to the purchase of a 1987 535is this
last weekend.  I sold my previous 535is and regretted it
ever since.  The car is all original, down to 4 brand new
Michelin TRX tires.  The car has 112,000 original miles with
all original paint a Supersprint exhaust, Dinan chip, big
bore throttle body and K&N cold air intake.  The car is
working great but has an interesting ABS function.

When coming to a stop the ABS will cycle once.  You can feel
the pedal.  I have never felt this type of ABS behavior on
any car with ABS.  It seems like the speed sensors think
there is a difference in wheel speed.
Any thoughts would be appreciated.

Georg
87 535is - the "MOCK 5" is back
96 328is - daily driver
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