Audi A4 Avant 1999 Wheel Motion Sensors
ArthurX
I'm faced with the doubtful pleasure of renewing a front outer CV joint
boot. I've read up fairly extensively on the subject and think I know of
most of the pitfalls, the notorious pinch bolt et al. The one thing
remaining unresolved in my mind is the removal of the motion detector sensor
for the ABS system. All the accounts I have read glibly mention removing the
sense head without any reference as to the best way to do so. I have held
the outer part of the head as tightly by hand as I can manage and it will
not move at all. There are a couple of extremely inviting flats on the head
of the sensor which just invite the application of spanner pressure, this
I'm reluctant to do as the head appears to be plastic and the last thing I
want to do is to damage it (the cable disappears to places unknown and there
are no visible junctions, hence it could be quite tricky, as well as
expensive to renew).
Has anyone experienced similar problems? Did they find a a solution? Has
anyone broken the head of the sensor attempting to remove it? If so, was it
easy/ expensive to renew? Where is the connector for the feed wire for this
item?
Thanks kindly for all assistance.
TonyJ
ArthurX wrote:
The ABS sensor is removed by pulling straight out. If yours doesn't do that it
may have corrosion around it. When installed there is a grease used to keep them
from seizing.
OTOH, I am not sure why you want to remove it at all because you can remove the
axle by tilting the strut once it is loose and the ABS sensor has enough wire to
allow this.
If you do remove it you will need to get a part called an ablative tip to place
over it when inserting it again. The process is to replace th axle and then push
the ABS sensor back in until it hits the hub on the axle. When the axle turns it
wears away the ablative tip and the correct clearance it maintained.
The connection to unplug the ABS sensor is reached by removing the plastic wheel
well liner and you will see it.
The way I move the strut to remove the axle is to first jack up both sides of
the front of the car to remove pressure on either side from the sway bar. Then
remove the three nuts on the top of the strut (top of the wheel well in side the
hood). The rotate the strut down and remove the axle. this way you do not need
to mess with the pinch bolt from hell.
ArthurX
"TonyJ" <tonyj...@nospamvisi.com> wrote in message
news:131g413...@corp.supernews.com...
Dear Tony
Thanks for the extremely informative and helpful reply. The reason I wanted
to remove the motion sensor was because in all the procedures I have read
this part needs to be moved, if it doesn't, then that's great news. I was
pondering on the necessity to remove it but decided that the most likely
reason was the amount of free wire on the component being insufficient but
if there's enough, that's also good news.
I was most interested to hear of your avoidance of the pinch bolt by
removing the top anchorage of the strut, there is one account I've seen of
tackling the task by loosing the bottom anchorage but your approach appeals
a lot more - less corrosion, straight back, good access etc.
I made myself a screw powered extractor for the pinch bolt, loosely modelled
upon the official Audi tool, with mine being far heavier in construction and
I would have been interested to see if it worked, though not very
interesting if it failed and destroyed the pinch bolt in the process. Have
you ever used the official Audi tool or heard of stories of it's success? It
seemed to me that the frequent approach of removing the bolt by percussion
probably failed by reason of access and that also the top arm being
supported in rubber bushes, this removing much of the shock from the blow.
I'd be pleased to hear your thoughts.
Thanks once again for the very helpful reply.
Kind Regards
Art
TonyJ
I haven't ever used the Audi tool for the pinch bolt but then I am just a shade
tree mechanic that like working on my car and friends. I have heard that the
tool works but success is dependent on the amount of corrosion. Most people who
attempt to remove the pinch bolt start after having a new replacement available
in case the old one is ruined.
Let us know how it goes.
ArthurX
Hello Tony
Yes I do have a new pinch bolt available, including the nut. What concerned
me was ruining the bolt in the attempt to extract to the point of being
unable to refit the nut, this being the point at which all boats are burnt -
no going back. I always worry to much.
I looked at the top attachment option today and it does look good.
Regards
Art