ABS Problem

[KentishRover]

Hi

I've had this problem for about 4 weeks now. Under light braking (but not heavy) it feels like the ABS is kicking in very slightly, although not fully, and only on the front offside wheel. It sounds a bit like gravel scraping against something.

I took the front wheels off to see if anything was stuck in there but all seems fine. The brakes still work very effectively and stop the car well. The ABS warning light came on the dashboard yesterday, and disappeared today.

Any ideas?

Thanks

[vincentfishing]

this happened on both mine(fronts) ,very intermittent and the speedo would stop only after 60 mph weird( drivers side), i unplugged ,pulled out cable and found where cable rubbed and cut out and rejoined , with the o/s it started to happen the day before mot, thought it ws probably intermittent break caused by cable stretch by steering, so unclipped it fomm rigid clip nearest sensor as it looked like cable was at tight angle,and yes end of problem, i think there prone to rubbing and internal breaks due to wear and tear of suspension and steering movements(and age) but you dont neccessarily need new sensors, a repair is cheaper and easier if you can find break

[KentishRover]

Ah so it could be the cables? Must admit I didn't think to check them. Is it particularly complicated to replace one?

Thanks

[vincentfishing]

the hard bit is getting the sensor out of the hub,i've read that it can be easy but the majority are well stuck in, my drivers side had to be drilled out which wasnt too hard ,but i never checked the cable first , if i had i woulndn't have replaced it, theres plenty on here to tell you how to do it ,what size drill, only thing is getting any bits out that drop into hub casing, hoover with small pipe taped to it might do the trick if you have a problem, isnt a particularly hard job, but repairing wires is easier

[Mike Noc]

Ah so it could be the cables? Must admit I didn't think to check them. Is it particularly complicated to replace one?

Thanks

You can check all the sensors and magnetic reluctor rings in the bearings with a voltmeter.

Better to diagnose the problem before changing anything as you can end up putting more faults on the system. :getmecoat:

[KentishRover]

Thanks, I'll have a look and see if the cable is being stretched anywhere.

[vincentfishing]

or worn through to wire, unplug under bonnet, pull through rubber grommet in wing and it streches out nicely to view in your hands, good luck.

[roverbarmy]

Jack up the car and check for rock on the wheel bearings. Excess play can cause the edges of the disc pads to catch on the rust on the edges of the discs.

[trikey]

A faulty wheel bearing can also cause this issue.

[DMGRS]

A faulty wheel bearing can also cause this issue.

That's what it turned out to be on a 75 I bought to repair and sell on - a right nightmare to replace! After 4 sensors things still weren't behaving so I sold it to someone that'd have more time to look at the issue - the chap ended up changing all 4 bearings as they all seemed worn (very high mileage car) and it behaved after that.

Usually the sensors tend to fail 'suddenly' and the bearings are what cause intermittent issues before worsening to a continuous state.
Both are here, if needed:
Front Wheel Bearing Kit - 75/ZT (http://www.dmgrs.co.uk/collections/abs-components/products/oem-rover-75-mg-zt-front-wheel-bearing-kit-nwb-rud100150)
Rear Wheel Bearing Kit - 75/ZT (http://www.dmgrs.co.uk/collections/abs-components/products/rover-75-mg-zt-rear-wheel-bearing-kit-rlb100292)
Front ABS Sensor - 75/ZT (http://www.dmgrs.co.uk/collections/abs-components/products/rover-75-mg-zt-front-abs-sensor-ssb000150)
Rear ABS Sensor - 75/ZT (http://www.dmgrs.co.uk/collections/abs-components/products/rover-75-mg-zt-rear-abs-sensor-ssb000160)

Good luck - there's a lot of guides on here for testing the ABS system, but they work best when the issue is present all of the time (ie a failed sensor).
It may be worth checking all 4 wheel bearings for play as a first move. :)

[KentishRover]

Thanks for that - will give it a thorough look when I have time next week. There are some rusty coloured deposits on the brake discs, particularly the wheel the issue seems to be coming from.

[Gemsathome]

Interesting, I had the sensor cable rubbing 3 weeks ago AFTER a full service.! Seems my garage, who are A1, must have reassembled the nearside plastic shield after changing the cambelt and water pump and stretched the sensor cable, it started making light grinding noises so I took it straight in next morning and they replaced the sensor FOC. :-)

[KentishRover]

Don't know if this is relevant but the steering arm on my car was changed in September - may have caused something like the plastic shield to rub against the cable.

[Jules]

Intermittent ABS warning and pedal vibration.
This is caused by momentary triggering of the modulator motor when ABS ECU thinks one of the wheels has slowed down during braking.



Cause 1
Faulty sensor due to water ingress via a chaffed cable.
Very common for bodge monkeys to break all the sensor cable clips when replacing brake pads etc so ABS cable rubs through on the tyre
(usually driver's front as that's the side the brake wear sensor cables should be securely fitted into all the original clips also.
The clips don't break if they are unhooked carefully, bit like a safety pin)

Cause 2
The rear back plates on the brakes on these cars are beginning to corrode through. (afterall they are 10 to 15 years old now)
The centre hole of the back plate expands with rust around where the stub axles are. This results in fouling of the wheel bearing seal which is also the ABS reluctor ring.
In bad cases the reluctor ring is completely worn away!
Before this happens the T4 or similar diagnostics will come with a message like " Rear LH sensor has incorrect number of teeth"
That is you clue there is something amiss at the rear.

Quality Remedy is simply to replace wheel bearing or hub assy and renew the back plate. (these were obsolete but now back in stock from Rimmers etc)

Economy remedy
Chisel away the flaky rust out of the middle of the backplate
(about 15mm all the way round, taking care NOT to damage the sensor)
Is to renew the rear bearing
(comes with new built in reluctor ring)


Cause 3
Soaked carpets where water sloshing round the under floor cable looms.
(either the left or right front to rear cable runs. The twisted pairs in these looms are from the rear ABS sensors and are very sensitive to moisture!)

[KentishRover]

Thank you - will have a look and see if it's any of those. Very helpful stuff on here as always, greatly appreciated.

[DMGRS]

A useful guide Jules - thanks for posting. :)

[KentishRover]

Just had a look - the ABS sensor cable is worn away in several places. When I fit the new one, is there any way to make sure it doesn't rub again?

[Jules]

Replace all the clips (if missing) which run along the inner wing and up the wheel arch liner.

See Rimmers parts lists for where they all go.
There's 3 or 4 along the cable run plus a clip on the brake flexi hose.

[DMGRS]

I've had to cable tie mine, as likewise the clips are missing. The OEM clips are a much better solution, though.

[Jules]

Before anyone else breaks these cable clips, they simply unhook open
(bit like a safety pin ) no need to break them as so many garages do :snowfight1:

[KentishRover]

Thanks all, new sensor cable ordered with new OEM clips. Will post a picture of the damage to the existing cable for reference if anyone comes across this thread.

[Jules]

Have a read of this from 2013

Again it's the consequences of shoddy careless work by the Bodge Monkeys
Quite frightening when it's yer brakes too


http://www.the75andztclub.co.uk/forum/showthread.php?t=160103

[KentishRover]

That is worrying. As I mentioned earlier in the thread, my local garage did work on that area of the car a few months ago when fitting new suspension. I don't know if the sensor cable was secured before the car had the work done, though, and obviously can't prove that.

If it was a result of their work, I would obviously be very unhappy - I pay a premium to get work done at the garage in question because they have a good reputation as a Rover specialist and you would hope that they know what they're doing. There have been several times before that they've said things that hint at a lack of knowledge of issues specific to these cars, though. It does make you wonder.

I checked the other side of the car to see if the sensor cable was damaged at all. It was in perfect condition and seemed more thoroughly secured with clips. I suppose there's no way of knowing if they messed it up, but I'll be sure to check over any work they do on my car in the future...

[Jules]

It's always the driver's side that has the broken clips !!
(usually caused by the changing of the brake pad wear sensor)

[KentishRover]

ABS Sensor cable replaced - still no luck. There is also some damage to the wear sensor cable - worse condition than the ABS cable was, actually. Could this be interfering with the ABS?

[Jules]

Get the codes read to see which corner is faulty.
Otherwise it's a guessing game !!

[KentishRover]

Well I had it in the garage, as there was a tonne of other work to do which I couldn't manage myself, so I asked them to have a look (they market themselves as MGR specialists). Turns out the backplates on both rear wheels were corroded and had damaged the reluctor rings, so both rear wheel bearings were replaced and the corrosion was sorted out on the backplates. Very annoying problem that was difficult to trace, but hopefully sorted out now.

[Jules]

Back plate corrosion very common now so we keep them in stock !

Has anyone a source for the rear reluctor ring/seals as it's a shame to have to change the whole bearing hub when there's nothing wrong with the bearing itself ?!!