Speed sensor

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steveskeggy

Active Member
Joined
Jul 4, 2011
Messages
188
Car
S55 AMG
Hi.
I have the ABS,BAS etc, warnings up on my dash.
The car is a 2003 S55AMG W220.
I have replaced everything from the ABS ECU to the wiring between the ECU, the wheel bearing and ring, and have had three different sensors, including a 10 quids worth of MB sensor, which was usless.
I think I may have found the problem.
I got a wheel bearing from ebay, I have since found out that this was not a good idea.
I understand that there should be a chamfer on the inside edge of the inner bearing, which fits over a ridge on the axle.
I believe this is causing my problem because I have stripped the hub back again, and taken the dust shield off, measuring the gap between the sensor and the ring, it is 1.62mm.
The question is, what should the gap be? Any ideas?
 
No Idea, but 1.62mm should be close enough for the sensor to read. Is this the system with a metal disc with holes in it or a ring with cut out's ? either way moving the ring/disc past the sensor should cause a measurable MiliVolt output on the sensor terminals, thats the starting point..usually.
 
Ring with the cut out.
The sensor is sending a signal, but its sporadic going from 0 to 17+ KHP.
I can read it on live data on my maxidas.
I read that the gap between the sensor and the ring should be 0.4 to 1.5mm, but this was not for a mercedes.
The gap even looks too big.
I have tried machining a better chamfer on the wheel bearing to see if that helps.
 
Is This on the front ??
 
Febi.
But I have my doubts because it says made in Poland on the inner bearing.
 
Febi.
But I have my doubts because it says made in Poland on the inner bearing.


Chances are it's the ring m8. I used a kit by " Lucas" that ended in disaster. I went and bought the full hub at mb in the end . Out of the box and on. All faults went away. If you have time swap the hubs left to right and see if the errors follow that hub. If you have a code reader.
 
Well, it looks like it was the gap.
I re-fitted the hub with the bearing that I had machined, and it worked straight away.
Both of the fronts are reading exactly the same speed at any speed, and they are both 1mph lower than the rears, which I put down to the non-standard wheel and tyre sizes (19 inch).
Unfortunately, I didnt check the gap, so I cant answer my original question.
No more warnings, no more codes, the cruise control works fine, and the steering is no longer heavy.
So, I am a happy today.
Now for the right front SAM...
 
Now I am a bit confused . Machining a chamfer on a bearing ???
Yes.
Put it in the lathe, run the chuck around 300rpm and use an inner cutting tool to gently cut thin slices at a time.
Finish it off with the lathe spinning at around 500rpm, with a Dremmel.
It comes up nice and smooth, and you dont take enough off to affect the strength of the bearing.
You are only cutting the inner race, this has, as best as I can describe it, a lip, which I took a fraction off, then re-cut the chamfer to better match the stub axle.
There may be a grinding tool to fit in the tailstock out there, but finding one during lockdown is difficult, if not impossible.
 

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