Rear ABS sensor: clarity needed after wheel rotation test

[goltho]

The car's been suffering from an ABS fault which has been intermittent but which is now occurring all the time. The ABS light has only come on once which TOAF reported as the O/S/R sensor. Makes sense as speedo etc is fine. I reset the code and it's not errored since although the fault continues.

I checked the voltage this afternoon whilst rotating the wheel. It varies between 0.70v and 1.75v. Thing is, if I rotate the wheel very slowly, the voltage does not fluctuate at all irrespective of whether I start the rotation with the high or low voltage showing. If I turn it around 1 revolution per 3 seconds (or faster), it switches to the alternative voltage and stays there up to & including when I stop. At no speed can I make it alternate as I expected.

Advice needed please on whether this confirms a faulty reluctor or sensor. Incidentally, the point where the fault is most noticeable is braking at around 30mph. The pedal pulses reasonably regularly e.g. 2-3 times per second for one or two seconds, then becomes more random as the speed falls off.

Thanks.

Dougie.

[ceedy]

our cars do suffer from rusty handbrake back plates , they swell/distort and then rub on / damage the ABS ring on the rear wheel bearing..


Worth pulling off the wheel/ disc etc. for a looksee.

C

[goltho]

Originally Posted by ceedy

Worth pulling off the wheel/ disc etc. for a looksee.

Well not really, cos whilst the reluctor might show signs of contamination, I doubt it will necessarily prove it's faulty. Plus the chances are that the bearing flange will remain on the shaft during the process. That's why I'm asking for some experience rather than pull parts off. Thanks.

Dougie.

[Arctic]

Hi Dougie.
Nine times out of ten when the rear ABS plays up it's the OS bearing, as above easy way to check is remove the brake disc drum, and have a visual look.

As you checked the voltage this afternoon whilst rotating the wheel. It varies between 0.70v and 1.75v

1

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3

as above most likely back plate as rust and it's got on to the ring.
4

if so clean it up for now, use some anti-rust fluid if you have some if not add a lick of paint, wipe clean the bearing if it comes free in one piece.
5

Re-fit and then see if the 5mph to 10 mph pulsing as gone.

If yes you now know its contamination from back plate or you need both back plates changing and a new bearing.

[goltho]

Originally Posted by Arctic

Nine times out of ten when the rear ABS plays up it's the OS bearing, as above easy way to check is remove the brake disc drum, and have a visual look.

Hey Steve, if the odds are that high, then it's almost beyond reasonable doubt (certainly guilty on the balance of probabilities...).

Originally Posted by Arctic

if so clean it up for now, use some anti-rust fluid if you have some if not add a lick of paint, wipe clean the bearing if it comes free in one piece

And guess who'll be fitting a new one if it doesn't. I shall proceed in a westerly direction and report back. Thanks for the input as ever.

Dougie.

[goltho]

I checked out prices & availability of a rear hub in anticipation that the bearing might not survive the removal for checking (part is RBL100292). GSF have them in stock for £55 discounted which is higher than (e.g) Autodoc (Ridex) at £35 delivered, but Ridex don't have a good press.

Scanned eBay out of interest and reliable aftermarket parts came in around £40+. However - I stumbled across GSF who sell on eBay which I never knew, and who had the self-same Drivetec part as in-store for £27.67 - exactly half their discounted store price - including delivery. Well guess wot. Arrives Wednesday so I'll change it anyway for that money. I may remove & clean up the sensor while it's stripped down as they can also put up a fight.

There are two GSF bearings left on eBay if anyone's in the market, links below.

Dougie.

Link to GSF rear bearing (1)
Link to GSF rear bearing (2)

[xsport]

yes GSF have been selling on ebay. recently i bought brembo front and rear pads for swmbo"s civic. mintex they sell as well. my thinking was that with them being a reputable supplier , i would not be getting chinese copies .... at those prices it was a no brainer. i have bought from them direct before and not had any issues. ...

[macafee2]

Dougie, if you do replace the bearing I'd like to take a look at the old one and what part has failed.

thanks

macafee2

[xsport]

you may be better buying a new sensor whilst your at it. you may well get away with cleaning the sensor face if your lucky. if not , the odds are stacked against removing the old one without damage. dmgrs does do them,at least they are guaranteed to work and last,unlike some cheapo ebay sensors. actually , when you look at his price for hub and sensor for the rear .. its not too bad at all . i fitted 2 new rears and sensors recently on mine and the bearings are good quality. anyway .. good luck !!

[goltho]

Originally Posted by xsport

yes GSF have been selling on ebay. recently i bought brembo front and rear pads for swmbo"s civic. mintex they sell as well. my thinking was that with them being a reputable supplier , i would not be getting chinese copies .... at those prices it was a no brainer. i have bought from them direct before and not had any issues. ...

I've used GSF for many years for different makes & models and without fail have found them excellent for service, quality and when necessary, returns. I'm guessing they may part out old slow stock on eBay - like Rover 75 stuff - so I've bookmarked their eBay store for future reference. Very happy.

I also decided today to order a new sensor (from DMGRS, £17.98 which is - unusually - way cheaper than the usual aftermarket stores) which arrives on the same say as the hub. Reason being that I've ended up with the luggage compartment trim and rear seat stripped out of the Tourer after (finally) accessing the sensor connector & wiring to carry out the test. The hub's coming off too which will expose the business end of the connector nicely, so I figured it's likely to be suffering the usual rust issues too and therefore makes sense to be able to remove it relatively easily when it's all stripped down anyway. Total cost should end up being £45 which gives me the fuzzies.