ABS Problem MG ZT-T - Page 11

FrenchMike · 3rd December 2016, 16:31

Quote:

Originally Posted by larryr123

Hi Mike, I had the front hub wheel bearing replaced with a new one, which has the reluctor ring integrated into it. It didn't show any missing marks on the tyre with the first new sensor.

That's what makes this such a mystery, because the second new sensor is now not picking up all the reluctor elements like the first new one did.

Regards Larry

Have you an idea of the gap value before and after ?

larryr123 · 3rd December 2016, 16:51

"Have you an idea of the gap value before and after ?"

Hi Mike, I don't know what the gap value means.
All I know is the sensors are standard and the wheel bearing was replaced with a brand new and identical to the old wheel bearing.
To be honest I think this was an unnecessary, had I not carelessly drilled too deep to get the old one out.

The whole problem started with the speedo going off and the ABS warning light coming on a couple of months back. Since then I drilled out the old sensor and possible damaged the reluctor ring, hence the replacement was done. Since then I have no ABS warning lights and it passed the MOT with the brake judder.

All the sensors are the same length, there is no room for play in the receptor hole for the sensor, they fit really tight, and they are side facing onto the hub ring, so I can't see how the gap would vary from one sensor to the next - it's a standard fit.

Larry

FrenchMike · 3rd December 2016, 17:19

Quote:

Originally Posted by larryr123

"Have you an idea of the gap value before and after ?"

Hi Mike, I don't know what the gap value means.
All I know is the sensors are standard and the wheel bearing was replaced with a brand new and identical to the old wheel bearing.
To be honest I think this was an unnecessary, had I not carelessly drilled too deep to get the old one out.

The whole problem started with the speedo going off and the ABS warning light coming on a couple of months back. Since then I drilled out the old sensor and possible damaged the reluctor ring, hence the replacement was done. Since then I have no ABS warning lights and it passed the MOT with the brake judder.

All the sensors are the same length, there is no room for play in the receptor hole for the sensor, they fit really tight, and they are side facing onto the hub ring, so I can't see how the gap would vary from one sensor to the next - it's a standard fit.

Larry

Hum,if only few sectors are missing,i would say ,your reluctor ring is damaged !

Mike Noc · 3rd December 2016, 20:56

Quote:

Originally Posted by larryr123

All the sensors are the same length, there is no room for play in the receptor hole for the sensor, they fit really tight, and they are side facing onto the hub ring, so I can't see how the gap would vary from one sensor to the next - it's a standard fit.

Larry

Yes that's what I thought, but when I had a similar problem on a rear bearing I checked the signal with the bearing and sensor in my hand and all the magnetic segments were picked up.

Fitted back on the car random segments were missed when rotating the wheel slowly. It could only be the air gap, so I filed 1.4mm off the bracket and eveything has worked fine since.

At the time I put it down to the combination of an aftermarket sensor and bearing being not quite as compatible as they should be.

larryr123 · 3rd December 2016, 21:24

Mike, Your problem with the air gap was related to the rear hub/sensor. On the rear the tip of the sensor faces down onto the reluctor ring, so filing the bracket down will bring the tip closer to it, which solved your problem.

On the front hubs the reluctor ring slots in with the ring facing the side of the sensor magnet, not the tip. My assumption therefore is that filing won't make an iota of difference as this won't bring the sensor any closer to the reluctor ring.

Regards Larry

larryr123 · 3rd December 2016, 21:29

Also the reluctor ring is brand new and it tested well for all the pulses on the 1st new sensor.

I think this is a pretty indeterminate problem, since random problems keep arising no matter what parts are replaced or adjustments made.

And there are no tests that the manufacturer has devised to cover the proper function of the ABS system.

Personally I want it disabled, but I want to be able to maintain a speedo and no warning lights -- Is this possible?

Regards Larry

larryr123 · 3rd December 2016, 21:46

Just picked this info up :-

I guess this is the most relevant statement in the paragraphs below :-
----Most sensors on newer vehicles, however, do not have an adjustable air gap."----

"SENSOR AIR GAP
The distance or "air gap" between the end of the sensor and its ring is critical. A close gap is necessary to produce a strong, reliable signal. But metal-to-metal contact between the sensor and its ring must be avoided since this would damage both. The air gap must not be too wide, on the other hand, or a weak or erratic signal (or no signal) may result.

The air gap on some wheel speed sensors is adjustable, and is specified by the vehicle manufacturer. The gap will vary from one application to another so always refer to the exact specifications for the vehicle when adjusting the sensor. Most sensors on newer vehicles, however, do not have an adjustable air gap."

Mike Noc · 3rd December 2016, 22:02

Quote:

Originally Posted by larryr123

Mike, Your problem with the air gap was related to the rear hub/sensor. On the rear the tip of the sensor faces down onto the reluctor ring, so filing the bracket down will bring the tip closer to it, which solved your problem.

On the front hubs the reluctor ring slots in with the ring facing the side of the sensor magnet, not the tip. My assumption therefore is that filing won't make an iota of difference as this won't bring the sensor any closer to the reluctor ring.

Regards Larry

Yes of course that is true Larry. But you could still have exactly the same problem with a slightly too large air gap between sensor and reluctor due to aftermarket parts not being compatible. If that is the case then a replacement part will be required.

Interestingly with the problem I had all the segments were read until the rotation was slowed right down, and then random segments were missed.

One other check you could do to eliminate a wiring fault is to plug the sensor into one of the other plugs and see if things improve. I made up an extension cable from some old speaker twin core with an ABS plug and socket from a scrapper so any sensor could be connected to the OSF and the speedometer used as a diagnostic. Here it is being used to check a hub prior to fitting.

[IMG]

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larryr123 · 4th December 2016, 12:23

"But you could still have exactly the same problem with a slightly too large air gap between sensor and reluctor due to aftermarket parts not being compatible."

Mike on the front sensors, appreciate you had a rear sensor problem, there is no tolerance in the way the sensor fits into the hub.

If you filed the sensor side itself, you would in fact increase the size of the air gap, because the thing is reading side on when it is facing the reluctor ring.

Filing can not serve any purpose on a front sensor, does everyone else agree with this, or am I missing something?

Both the new sensors I have tried have been the same length and thickness and the positioning of the sensor inside the hole can not be varied because it is screwed into place with a single screw which is also in a fixed position and allows no play of movement to re position the sensor.

Larry

larryr123 · 4th December 2016, 12:29

""One other check you could do to eliminate a wiring fault is to plug the sensor into one of the other plugs and see if things improve.""

Mike, if the sensor is applied to another wheel, I would need to drill out one of the old one's and this would just create more problems. Given that all the other 3 wheels seem to be giving regular pulses, I'd want to leave them alone. It takes at least an hour to remove an old sensor and there is every possibility I would damage one of the reluctor rings in the same way that I did with the front right sensor.

3rd December 2016, 21:46	#107
larryr123 Avid contributor MG ZT-T Join Date: Aug 2016 Location: larryr123 - Biddenham, Bedfordshire Posts: 224 Thanks: 27 Thanked 19 Times in 17 Posts	Air Gaps Just picked this info up :- I guess this is the most relevant statement in the paragraphs below :- ----Most sensors on newer vehicles, however, do not have an adjustable air gap."---- "SENSOR AIR GAP The distance or "air gap" between the end of the sensor and its ring is critical. A close gap is necessary to produce a strong, reliable signal. But metal-to-metal contact between the sensor and its ring must be avoided since this would damage both. The air gap must not be too wide, on the other hand, or a weak or erratic signal (or no signal) may result. The air gap on some wheel speed sensors is adjustable, and is specified by the vehicle manufacturer. The gap will vary from one application to another so always refer to the exact specifications for the vehicle when adjusting the sensor. Most sensors on newer vehicles, however, do not have an adjustable air gap."

3rd December 2016, 16:51	#102
larryr123 Avid contributor MG ZT-T Join Date: Aug 2016 Location: larryr123 - Biddenham, Bedfordshire Posts: 224 Thanks: 27 Thanked 19 Times in 17 Posts	"Have you an idea of the gap value before and after ?" Hi Mike, I don't know what the gap value means. All I know is the sensors are standard and the wheel bearing was replaced with a brand new and identical to the old wheel bearing. To be honest I think this was an unnecessary, had I not carelessly drilled too deep to get the old one out. The whole problem started with the speedo going off and the ABS warning light coming on a couple of months back. Since then I drilled out the old sensor and possible damaged the reluctor ring, hence the replacement was done. Since then I have no ABS warning lights and it passed the MOT with the brake judder. All the sensors are the same length, there is no room for play in the receptor hole for the sensor, they fit really tight, and they are side facing onto the hub ring, so I can't see how the gap would vary from one sensor to the next - it's a standard fit. Larry

3rd December 2016, 21:24	#105
larryr123 Avid contributor MG ZT-T Join Date: Aug 2016 Location: larryr123 - Biddenham, Bedfordshire Posts: 224 Thanks: 27 Thanked 19 Times in 17 Posts	Mike, Your problem with the air gap was related to the rear hub/sensor. On the rear the tip of the sensor faces down onto the reluctor ring, so filing the bracket down will bring the tip closer to it, which solved your problem. On the front hubs the reluctor ring slots in with the ring facing the side of the sensor magnet, not the tip. My assumption therefore is that filing won't make an iota of difference as this won't bring the sensor any closer to the reluctor ring. Regards Larry

3rd December 2016, 21:29	#106
larryr123 Avid contributor MG ZT-T Join Date: Aug 2016 Location: larryr123 - Biddenham, Bedfordshire Posts: 224 Thanks: 27 Thanked 19 Times in 17 Posts	Also the reluctor ring is brand new and it tested well for all the pulses on the 1st new sensor. I think this is a pretty indeterminate problem, since random problems keep arising no matter what parts are replaced or adjustments made. And there are no tests that the manufacturer has devised to cover the proper function of the ABS system. Personally I want it disabled, but I want to be able to maintain a speedo and no warning lights -- Is this possible? Regards Larry

4th December 2016, 12:23	#109
larryr123 Avid contributor MG ZT-T Join Date: Aug 2016 Location: larryr123 - Biddenham, Bedfordshire Posts: 224 Thanks: 27 Thanked 19 Times in 17 Posts	"But you could still have exactly the same problem with a slightly too large air gap between sensor and reluctor due to aftermarket parts not being compatible." Mike on the front sensors, appreciate you had a rear sensor problem, there is no tolerance in the way the sensor fits into the hub. If you filed the sensor side itself, you would in fact increase the size of the air gap, because the thing is reading side on when it is facing the reluctor ring. Filing can not serve any purpose on a front sensor, does everyone else agree with this, or am I missing something? Both the new sensors I have tried have been the same length and thickness and the positioning of the sensor inside the hole can not be varied because it is screwed into place with a single screw which is also in a fixed position and allows no play of movement to re position the sensor. Larry

4th December 2016, 12:29	#110
larryr123 Avid contributor MG ZT-T Join Date: Aug 2016 Location: larryr123 - Biddenham, Bedfordshire Posts: 224 Thanks: 27 Thanked 19 Times in 17 Posts	""One other check you could do to eliminate a wiring fault is to plug the sensor into one of the other plugs and see if things improve."" Mike, if the sensor is applied to another wheel, I would need to drill out one of the old one's and this would just create more problems. Given that all the other 3 wheels seem to be giving regular pulses, I'd want to leave them alone. It takes at least an hour to remove an old sensor and there is every possibility I would damage one of the reluctor rings in the same way that I did with the front right sensor.