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[bkorven]

brilliant .glad you sorted it.
and also its nice for someone like yourself to come on afterwards and say the problem has been fixed.so many forums give helpfull advice to people and you never hear a word after !

Thank you! Hehe, I've several times found myself reading similar threads on different topics where I have been dying to know about the outcome and what fixed a problem. I'm grateful for everyone trying to help out, so to come back with answers to what was wrong is the least I can do.

[cam.in.head]

not having a front one to hand to look at but i assume the design is physically similar to the rears .the sensor 'pick up area' is exactly in line with the mounting lug.i wonder if replacements are identical or could be off centre in any way ? explaining the rotation difference or the body depth is in any way slightly different.?   as mentioned,replacing (or at least checking/cleaning) the toothed ring would at least make that part eliminated.

[Doctor Gollum]

Rears are a ring on the drive shaft and might be available separately.

Fronts are cut into the rear face of the front hub and can only be replaced as a complete front hub bearing and flange assembly.

[cam.in.head]

yes i realise that.i was just trying to offer some advice regarding the sensor orientation and operation.

[bkorven]

not having a front one to hand to look at but i assume the design is physically similar to the rears .the sensor 'pick up area' is exactly in line with the mounting lug.i wonder if replacements are identical or could be off centre in any way ? explaining the rotation difference or the body depth is in any way slightly different.?   as mentioned,replacing (or at least checking/cleaning) the toothed ring would at least make that part eliminated.

I could not tell a difference between the replacement sensors and the ones I had before. The thought has crossed my mind, that there could be a slight difference, although the OEM number matches.

Either way, I am very excited to replace the hubs and perform new measurements. They were ordered today.

By the way; Haynes manual states the hub nut to be torqued to 320 Nm. That sounds extremely high. Thoughts on this? My biggest torque wrench goes to 210 Nm, and I'll probably turn it some extra degrees afterwards and be happy.

[Doctor Gollum]

210 is 65% of 320... it only holds the wheel on, so be prudent to obtain a torque wrench that can at least pretend to hit 320 Nm.

As an aside, if you go with your original idea, there's a reasonable chance that you overtighten the front hubs, causing the bearings to bind up once there's some heat in them. And that's a whole new level of inconvenience.

[Andy B]

.....
My biggest torque wrench goes to 210 Nm, and I'll probably turn it some extra degrees afterwards and be happy.

That exactly what the local garage said he'd done when I gave him a hub/bearing to fit to my Omega. I never had a subsequent problem

[cam.in.head]

overtightening theoretically can only strip or break the nut or thread. itwont actually overtighten the bearing as its 2 thrust bearings back to back and touching each other.

[johnnydog]

I thought the front hub tightening is a 3 stage process (I haven't got the exact figures to hand as I'm not at home) -
1- tighten to ?? Nm (a relatively low figure capable of being attained with most torque wrenches)
2- angle tighten
3- angle tighten
That's how I did my last front hub change as per Haynes (I think)?

[BazaJT]

No according to Haynes the hub nut is tightened to 320Nm/236lb/ft no angle tightening is involved.Angle tightening is mentioned for anti roll bar bearing bracket bolts,front subframe, lower suspension arm pivot bolts and strut to steering knuckle.

[johnnydog]

No according to Haynes the hub nut is tightened to 320Nm/236lb/ft no angle tightening is involved.Angle tightening is mentioned for anti roll bar bearing bracket bolts,front subframe, lower suspension arm pivot bolts and strut to steering knuckle.

Yes, you are right Baza - my mistake.... The more I think about it (it was some years ago!) I actually changed the complete knuckle as a whole unit with the hub, as the original brake shields were rotten as a pear - I didn't actually remove /  change the hub / bearing. The angle tightening sequence I mentioned was actually for the front strut bolts...

[Doctor Gollum]

overtightening theoretically can only strip or break the nut or thread. itwont actually overtighten the bearing as its 2 thrust bearings back to back and touching each other.

So are the front bearings on the S Class, except rather than tightening to a torque setting they are set to a specific amount of play at the hub face.

Point being, that they have a torque setting for a reason and 210 Nm plus a pinch of wishful thinking simply won't cut it.

[sjc]

not having a front one to hand to look at but i assume the design is physically similar to the rears .the sensor 'pick up area' is exactly in line with the mounting lug.i wonder if replacements are identical or could be off centre in any way ? explaining the rotation difference or the body depth is in any way slightly different.?   as mentioned,replacing (or at least checking/cleaning) the toothed ring would at least make that part eliminated.

I could not tell a difference between the replacement sensors and the ones I had before. The thought has crossed my mind, that there could be a slight difference, although the OEM number matches.

Either way, I am very excited to replace the hubs and perform new measurements. They were ordered today.

By the way; Haynes manual states the hub nut to be torqued to 320 Nm. That sounds extremely high. Thoughts on this? My biggest torque wrench goes to 210 Nm, and I'll probably turn it some extra degrees afterwards and be happy.

210 will be enough to let you drive it to a garage for a final torque-up with the right equipment.

[bkorven]

Thanks for all the replies.

Unfortunately, the problem persists. Now, though, I am almost completely certain it is all about signal strength.

The wheel hub assemblies were replaced in the front. And they were torqued to 320 Nm, according to specification New reluctor rings gave no improvement.







By rotating the sensors inside their mounting hole on the steering knuckle, and thus varying the signal strength for some reason, I have found that at what speed ABS is activated seems directly proportional. "Sweet spot" leads to the ABS activating just before coming to a stop, at perhaps 5 km/h. The closer I rotate the sensors back to their original position, the higher the speed at which ABS starts intervening. And with the sensors in their original position, ABS-light also comes on.

Note that front left and front right sensor seem to perform identically.

So my reflections right now are:
 - Could the signal be weak due to bad connection to ground?
 - Do front left and front right wheel speed sensors share ground?
 - Why would this problem arise after replacing front suspension along with new sensors?

This is the only ground I've found under the hood. Can someone confirm if this could be where the sensors ground?:




I guess my next step will be to check wiring, and I'll also test supplying a new temporary ground.

[LC0112G]

I've only played with Carlton/Senator ABS, not Omega B, and it might be different - but.....

There is no ground on the sensors. The two sensor wires are differential all the way to the control unit. Infact the resistance to ground of both terminals is many hundreds of K-ohms. If either terminal is somehow shorted to ground, the ABS fault light comes on.

As I say - on the Carlton/Senator.