ABS Problem MG ZT-T

larryr123 · 11th August 2016, 15:09

Hi -- I have an MG ZT-T CDti Diesel. Developed an ABS brake pedal judder problem recently and struggling to clear it.
ABS light came on 2 weeks ago and speedo failed. Unplugged ABS fuse and cleaned it and reinstalled it - worked OK, then did it again. Same procedure cleared it.
Since then the ABS light has stayed off but experienced brake pedal judder on braking, as the ABS is coming in erroneously. I confirmed it was an ABS problem by removing fuse again and braking went back to normal, no judder.

Replaced sensor on front right, thinking this would be the cause of an intermittent fault causing the speedo to go off in the first place.
Still had judder at various braking speeds, so took it to garage to be tested. £40 lighter, there was no definite conclusion. Static test showed fault on front right and one on rear right. Cleared faults and took it for a test. Retested it and faults didn't show. Also tried a wheel by wheel test rotating the wheels and recording the variation in voltage - no abnormalities found, they all showed voltages that rose and fell pretty much the same.

Next step - took off rear hubs (that have integrated ABS reluctor rings), cleaned up the rusty back plates (told these could cause the problem), cleaned stub axles and the hubs. Reassembled and it was much improved, ABS not kicking in on general driving, however, it still kicks in at very low speed, almost a few miles per hour.

I noticed on the rear Hubs, one hub had what looked like a brass ring on the outside with oval holes cut out at intervals - I assumed this was the reluctor ring, but there wasn't one on the rear nearside hub.

Does this make a difference, i.e. is this brass ring the actual magnetic reluctor ring or is it actually embedded into the hub? As it's been working fine since hubs were last changed in October 2014, I'm at a loss to know what to do next and what could be causing this to judder at low speeds, and yet no ABS light is coming on and no faults recorded.

I guess the ABS is working OK but the signals going back to the ABS control unit are such that it thinks the wheel is locking, but only at low speeds.

Any help welcome.

11th August 2016, 15:09	#1
larryr123 Avid contributor MG ZT-T Join Date: Aug 2016 Location: larryr123 - Biddenham, Bedfordshire Posts: 224 Thanks: 27 Thanked 19 Times in 17 Posts	ABS Problem MG ZT-T Hi -- I have an MG ZT-T CDti Diesel. Developed an ABS brake pedal judder problem recently and struggling to clear it. ABS light came on 2 weeks ago and speedo failed. Unplugged ABS fuse and cleaned it and reinstalled it - worked OK, then did it again. Same procedure cleared it. Since then the ABS light has stayed off but experienced brake pedal judder on braking, as the ABS is coming in erroneously. I confirmed it was an ABS problem by removing fuse again and braking went back to normal, no judder. Replaced sensor on front right, thinking this would be the cause of an intermittent fault causing the speedo to go off in the first place. Still had judder at various braking speeds, so took it to garage to be tested. £40 lighter, there was no definite conclusion. Static test showed fault on front right and one on rear right. Cleared faults and took it for a test. Retested it and faults didn't show. Also tried a wheel by wheel test rotating the wheels and recording the variation in voltage - no abnormalities found, they all showed voltages that rose and fell pretty much the same. Next step - took off rear hubs (that have integrated ABS reluctor rings), cleaned up the rusty back plates (told these could cause the problem), cleaned stub axles and the hubs. Reassembled and it was much improved, ABS not kicking in on general driving, however, it still kicks in at very low speed, almost a few miles per hour. I noticed on the rear Hubs, one hub had what looked like a brass ring on the outside with oval holes cut out at intervals - I assumed this was the reluctor ring, but there wasn't one on the rear nearside hub. Does this make a difference, i.e. is this brass ring the actual magnetic reluctor ring or is it actually embedded into the hub? As it's been working fine since hubs were last changed in October 2014, I'm at a loss to know what to do next and what could be causing this to judder at low speeds, and yet no ABS light is coming on and no faults recorded. I guess the ABS is working OK but the signals going back to the ABS control unit are such that it thinks the wheel is locking, but only at low speeds. Any help welcome.