vinny1275
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| posted on 23/12/08 at 09:23 AM |
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Tintop ABS weirdness
Morning all,
Hope someone has an idea what might be going on here...
background story:
The tintop (Y reg VW Passat TDi) needed a service and new front brakes. I did the brakes (discs and pads), noticed that one of the CV boots was split,
and asked them to replace the boot while they serviced it (I hate that job).
Now it's back, sometimes when I'm braking gently approaching a junction or something, the ABS will trip while I'm doing about 5 mph.
I can feel the juddering in the pedal (and hear it, it's annoying!). If I come off the brake the ABS will stop, and if I force the pedal down
harder I can get past the ABS and stop the car in a hurry.
What could cause this? I think that either one brake is grabbing, and the ABS is working properly, or something is tripping the ABS off when it
shouldn't....
Any ideas on how I can prove one or the other?
Cheers
Vince
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Danozeman
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| posted on 23/12/08 at 09:28 AM |
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Cv grease covering the abs ring?? Damaged ring on that side?
Could even be the pads fitted wrong. Take thw eheels off and have a look.
Dan
Built the purple peril!! Let the modifications begin!!
http://www.eastangliankitcars.co.uk
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zilspeed
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| posted on 23/12/08 at 09:30 AM |
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Could be a misaligned ABS sensor, or possibly now dirty with grease or damaged after the work at the CV joint.
If you can get it plugged into VAG COM you can bring up the scope which indicates wheel speeds. The odd one out is the sensor giving the erroneous
information. That's how I identified that my OSR ABS sensor was the bad one.
If you can't get access to VAG COM, you could try getting the garage that did the work to read the ABS ECU for any stored fault info, but my
first call would be VAG COM seeing as I have it 
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Mr Whippy
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| posted on 23/12/08 at 09:32 AM |
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Perhaps the wheel speed sensor is contaminated since its right next to the CV boot. I think if it detects no pulsing signal it assumes the wheel is
not rotating and hence thinks the cars skidding, especially if the other wheels are saying the cars moving. Also on my old vectra the flat cog like
bits on the CV joint had rusted so much away they no longer produced a correct signal and the ABS had just given up and registered a fault.
blimey you two are awake this morning 
[Edited on 23/12/08 by Mr Whippy]
Fame is when your old car is plastered all over the internet
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dinosaurjuice
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| posted on 23/12/08 at 09:44 AM |
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a similar thing was happening on a friends rover 420. on that car the inductance ring (think thats what its called) was pressed onto the driveshaft
and it had come loose. at slow speeds it rubbed against the hub and not rotate at all. fine when initially pulling away, but sends ABS crazy when
slowing down.
will
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Agriv8
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| posted on 23/12/08 at 09:57 AM |
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Hi Vince.
I would pop the ABs sensor and have a look. If that looks Ok Check the have not squashed the wireing to the Abs sensor.
Ps my passot TDI 110 R reg 214k miles is going up for sale this week as just got a 54 plate (TDI 130) on with a measly 118k on.
Have the haynes manual if required.
ATB
Agriv8
Taller than your average Guy !
Management is like a tree of monkeys. - Those at the top look down and see a tree full of smiling faces. BUT Those at the bottom look up and see a
tree full of a*seholes .............
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f1ngers
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| posted on 23/12/08 at 10:28 AM |
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As suggested by other posters it is most likely the ABS sensor is misaligned or the ABS ring has got contaminated when the CV boot was done. I had
exactly the same problem on my Audi after changing the CV boot!
Pull out the ABS sensor. If you have an airline blow out the ABS ring through the hole for the ABS sensor or use some brake cleaning spray or similar.
Give the ABS sensor a good clean and put a bit of copaslip or similar on the sensor and clamping sleeve surfaces. Re-insert the sensor and push all
the way in until you feel it contact the ABS ring (turning the hub helps to 'feel' when it is all the way in). Then back out the sensor
slightly and rotate the hub to check it is not making contact with the ring and that should do it.
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minitici
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| posted on 23/12/08 at 10:42 AM |
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If the reluctor ring on one of your CV joints has cracked then you can get this symptom.
There is a company which manufactures replacement rings for most popular cars.
Linky
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britishtrident
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| posted on 23/12/08 at 12:12 PM |
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Yeap sounds like either a cracked reluctor ring or it is just possible the cv joint clip is loose.
Unlikely to be the sensor itself --- the diagnostic clue is the early cut in to the abs at slow speed, sensor faults tend to be connection
failures and illuminate the ABS light as soon as the ignition is switched on and disable the ABS.
The reluctor rings are usually a shrink fit on the CV joint --- water gets underneath causes rust which cracks the reluctor ring.
A lot of more recent cars are showing this problem after only 4 years or so as CV joints don't appear to have any corosion protection.
Many of latest model now have the reluctor ring built into the wheel bearing.
Reluctor rings are available off the web but shop around as the price varies greatly -- 10 pounds each to 60 for a pair.
Always change both sides --- the other usually fails within weeks or less.
[Edited on 23/12/08 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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vinny1275
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| posted on 23/12/08 at 12:52 PM |
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Thanks for all the replies chaps - the guys in the garage said they had a job to get the hub off so the reluctor ring may have been damaged. More time
under the car then!!
Cheers
vince
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