How to adjust ABS Sensor / Tone Ring clearance?

JDK_Ent

Active member
Joined
Dec 30, 2008
Location
Woodstock IL
TDI
*** SOLD *** 2005 AIV BEW Engine; 185k miles. Was a GREAT car but needed a calmer, quieter (but still fun) car.
My ABS was kicking in at low speeds upon stopping, and it got worse when my front hub was recently replaced along with the front wheel bearing. VAG-COM showed that the front left sensor was losing signal below 3km/hr. I replaced the sensor (long story, the old one needed to be convinced to come out) and now with the new sensor, signal is lost below about 17km/hr. My Bentley manual shows a 0.3mm clearance is required between the tone ring and the sensor, but my new BWA sensor measures more like 3mm.

That's the background. Does anyone know if the 0.3mm clearance is correct? Is the clearance issue more likely to be caused by the new hub being incorrectly installed, or by a mis-adjusted ABS sensor? Can the ABS sensor even be adjusted for depth? The new one was an unbelievable PITA to install and took some whittling with a knife to get in, and I hate to remove it again if I don't have to.
TIA,
Joe N9OK
 

JDK_Ent

Active member
Joined
Dec 30, 2008
Location
Woodstock IL
TDI
*** SOLD *** 2005 AIV BEW Engine; 185k miles. Was a GREAT car but needed a calmer, quieter (but still fun) car.
Update: I removed the sensor and whittled some more (to slightly decrease the diameter so it would fit correctly). Now it slides in with only a little resistance, and the clearance has decreased to appx. 2mm. It is fully seated. Wheel speed is now sensed down to about 8km/hr. The clearance on the other front wheel is very small and it senses correctly down to 1km/hr.

So the question remains, why is there such a large gap between the sensor and the tone ring? Is it possible that the hub was improperly assembled onto the car? Any suggestions as to what to do about this?
 

Alchemist

Veteran Member
Joined
Nov 3, 2007
Location
Lethbridge, Alberta
TDI
'04 ALH Golf
When I had to replace one, I found the hole the sensor goes in had rusted and was smaller than it should be. Cleaning the hole left a good fit for the sensor, and there was no problem with low speed braking. Try a small round file to clean the hole and see if the sensor will sit in there better.

Paul
 

Curious Chris

Top Post Dawg
Joined
Jun 11, 2001
Location
Pineview GA
TDI
Jetta Wagon 2003 RIP Rockford IL
Update: I removed the sensor and whittled some more (to slightly decrease the diameter so it would fit correctly). Now it slides in with only a little resistance, and the clearance has decreased to appx. 2mm. It is fully seated. Wheel speed is now sensed down to about 8km/hr. The clearance on the other front wheel is very small and it senses correctly down to 1km/hr.

So the question remains, why is there such a large gap between the sensor and the tone ring? Is it possible that the hub was improperly assembled onto the car? Any suggestions as to what to do about this?
It is possible the hub was not seated all the way into the bearing. Though it would seem the torque on the nut would have pushed it all the way in. I just did wheel bearings and we used the ABS sensor as a double check that we were all the way there.
 

JDK_Ent

Active member
Joined
Dec 30, 2008
Location
Woodstock IL
TDI
*** SOLD *** 2005 AIV BEW Engine; 185k miles. Was a GREAT car but needed a calmer, quieter (but still fun) car.
I used a rat-tail file to better clean out the hole, but the sensor, fully seated, still had excessive clearance to the tone wheel. I then used a file to remove metal from the mating surfaces on both the steering knuckle and the sensor until the clearance was reduced. Now the sensor detects down to 1km/hr, so the problem is solved.
Thanks to the suggestions. I suspect that Curious Chris is correct that the bearing wasn't fully seated, but it's too late to fix it now.
 
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