Abs Fault - 2001 307 hdi

I would like to share with the group another 'issue' I've had with my 307.
It is now resolved but seems worth remembering / sharing.

Ive had a problem with slowspeed braking that i'm getting the ABS engaging
for no apparent reason and releasing one of the wheels. This started about
16 months ago and has got gradually worse.
The car stops well and passed its MOT in september whilst like this but is a
real pain.

I got my local tyre and brake supplier to check it out, and they couldnt
find any issues with the brakes etc. They recommended a local independant
garage that would be able to check the diagnostics.

They found no faults reported on the diagnostics and no warning lights etc.
They suggested a new ABS pump but warned it was offered as a 'most likely'
cause rather than dead cert. Given the likely cost, have a think about it
first. I decided to bear with it, so long as it stayed safe, and hope for a
fault to be recorded on the diagnostics.


5 MONTHS ON it went back for service and they again asked what I wanted to
do. This time whilst talking to my mechanic I mentioned that at 40000miles
another garage had replaced a front bearing.

They suggested this may be the missing link. If the bearing had been put in
wrongly (or the wrong bearing used) the ABS sensor on that side may be
fooled into thinking the wheel wasnt turning, and activating the abs pump.
They stripped it down and found whilst the bearing was fine, the circlip was
overlapping the sensor by a few millimeters. REFITTED CORRECTLY AND FAULT
VANISHES.

So despite being originally told the ABS unit is self contained and is most
often the cause of any problems, this clearly demonstrates this is not so.

Sometimes it pays to persist when there seems no obvious fault.

 

do. This time whilst talking to my mechanic I mentioned that at 40000miles

The first thing to check with any ABS problem is the wheel sensors. They
don't have to be far out to cause a problem. They also fail, but that should
show up on the diagnostics.

 

where in this case they were not @ fault, in fact, they were working
splendid.... only there sight was blocked.

true to say that if an ABS issue is to be solved, the most obvious
place to look are the wheel sensors.

garagists these day's just cannot seem to find faults without their
computer, and if nothing shows up, nothing is a fault....
if there is something at fault the only solution they can come up with
it replacing the unit that comes up in the computer, and still not
knowing what was wrong with it.

First thing i do in a garage is look if there are some senior
mechanics that are over 50 years of age. they are the ones that can
determine a fault by driving a car, listening to the engine, AND
listening to the costumer.

 

So despite being originally told the ABS unit is self contained and is

Useful information.
It's been done to death but I'll mention it again; the wheel sensors get
covered in metallic gunge from the brakes. This causes various problems,
like the abs warning lamp flashing intermittently to abs cutting in when
braking smoothly on a dry road. Halford sell a big aerosol can of brake
cleaner for about a fiver. Good spray and clean with an old toothbrush- job
done.
DaveK.

 

garagists these day's just cannot seem to find faults without their

Marc, this is so true.