Abs activating at low speed which sensor wire do I connect to?

[brianw]

Originally Posted by Mike Noc

I've had exactly the same problem Brian with the same test results and it was due to a build up of corrosion on the ABS sensor mount as I mentioned earlier.

Worth checking the bearing on that wheel for any play, and removing the hub and checking for any debris or damage on the reluctor strip first though - the hub has to be removed to get access to the magnetic reluctor.

The ABS sensor will more than likely be seized in so the easiest way to remove it if you have to is to hammer it out with a suitable drift with the hub off.

You mentioned earlier that no faults were logged, what are you using to read them?

I have a Sykes Pickavant ACR4 that can check the ABS system on our cars if you want to pop over and plug that in. I'm in Bordon.





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Thanks for the info.
It is always good to get the goods from someone who has been there before.
After I had checked it today my Grandson came around so I had other games to play.
I hope to get back to it this week, possibly after work Thursday as I think my wife is working late until then.
I did not detect any play in the hubs so I am hoping a clean up will do the trick.
I was using TOAF.
On the 1.8 it can access all the modules bar the engine - unless anyone knows better.
There was one error in the abs module when I first read it but that was there uncleared from 2016. A no signal from the OSF when an incorrectly routed cable broke.
I cleared that and took it for a good run but no errors were recorded.
I also tried logging the live data from the sensors to file to see if I could detect which wheel it was by comparing the speed each sensor was reporting. Also the state of brake switch, pump relay, and valve relay - value 0 or 1
I am not sure if it was the read rate low, or if my laptop went to sleep and it stopped recording but I did not gather as much data as I expected. About 600 entries if I recall correctly.
One thing was I noticed there was no speed in excess of about 20 kmh reported either it stopped before we got there or ????
I could see the brake value was 1 when brake was applied but the values for the pump and valve relays stayed in thier initial state. I was anticipating they may have shown a change when the fault manifested itself - unless it had stopped recording by then.

Sykes Pickavant eh, serious kit.
That is very kind of you, I may well take you up on that if the cleaning does not produce results.
In any case it would be good to meet you anyway as you are quite local to me.

Brian

[Arctic]

HI Brian.
Sorry I did not get back to you via your email, I have changed four rear ABS bearing over the last 18 months on various cars, and they have all been OS rear.

Therefore I would say that is the favourite, most likely back plate rust as either got between the sensor and the magnetic ring, or the ring it's self as got damage.

To clean the back plate correctly you will need to remove the disc drum, and the bearing hub.

I will post some photo's up tomorrow for you cheers Arctic.

[brianw]

Thanks Steve i will order a couple of stake nuts and take a look at that when i get a chance.
I replaced the discs/drums a few months back so was in there then although i had no reason to remove the hubs.

Brian

[Mike Noc]

Brian if you are doing both hubs then you can swap the nuts over, and unless you are very unlucky, you'll have a fresh bit of rim to stake down on each side.

Whilst you have the hubs off check for any corrosion of the backplates - if it lifts high enough it will end up damaging the magnetic reluctors.

[brianw]

I never thought of switching sides with the nuts to find a fresh piece.
I already have a pair on order but I will certainly remember that tip, thanks.
I see from Steve's photos how bad it can get toeards the centre of the backplate.
As I said i recently changed the discs but that area would have been obscured by the hub so i suppose it could be in a similar condition.
Still hoping to get the opportunity to take a look one evening this week.

Brian

[Arctic]

Hi Brian.
When you do get time to remove the drum discs it will be most important to check the back plates as any tiny bit of rust debris flaking off can and will damage the magnetic ring, as it will stick to the magnet the back plate in my photo above was really rusty and flaking that is why it damages the bearing.

I removed the bearing and as I did not have ant rear plates at the time I removed all the flaking rust, by scrapping and wire brushing the area was then treated with rust inhibitor ( Kurust ) which was painted on left to dry then I painted over it will hammerite.

Cleaned the drive shaft spindle thinly greased it ready for the new hub bearing with built in magnetic ring.

I also changed the sensor as I was not completely happy that is had not got damage also, the rear sensors a lot easier to remove than the front ones, I say this because once the hub as been removed you can access the sensor face and it can be tapped out from the hub.

I have added a few photo below, I did photo the full process from start to finish but it would take me a couple of hours to post up, I will get round to it in the near future, I know you will already know how to do what in is some of these quick time photo's below but it gives others a understanding also.

First crack the wheel studs, and jack the rear corner up.
1

Remove the wheel and keep studs together.
2

These are the tools I used 50 torx for the drum securing screw, 7mm allen key, a 7mm allen bit for the sliders, long nose pliers, rubber hammer and small steel hammer, 13mm ratchet spanner,
3

With the hand brake applied remove the torx screw
4

5

Next remove the brake caliper, spring first.
6

The rear dust caps
7

Using the 7mm Allen key tap the slider loose.
8

Once it as been cracked you can use the 7mm socket with the cut off bit in it, I know most will not have this so you would need to use the allen key, which is ok but a little slower.
9

10

With both sliders undone you can remove the caliper and pads off the disc
11

Tie the caliper back or up out of the way.
12

next remove the caliper bracket, 13mm bolts x 2 use a six sided spanner if you have one less chance of the head rounding off, because mine had been removed before when I changed the drum discs and brake pads I was able to use the ratchet spanner.

13

14

Lift the bracket free.
15

Now remove the hub cap using the flat blade screw driver

16
17

This will reveal the hub securing nut it will either be a 32mm or a 36mm.
18

Again using the flat blade screw driver open the tang on the nut.
19

Now at this stage I had to put the drum disc back because foolishly I had for got to remove the hub cap and open the tang earlier while the drum disc was still on like I had done a couple of days before when investigating the problem therefore it was easier to undo.

20

Once the nut is off you will find a collar remove this.
21

22

You can now slide off the bearing with the in built magnetic ring.
23

24

The back plate is now in good view
25

To be continued and amended Arctic.

[brianw]

Thanks for such a detailed post Steve.
A strange thing has happened though.
On Sunday night I pulled the abs fuse as it was freaking Manda out when she drove it with the abs kicking in and she needed to use it to get to work on Monday.
Of course I then got a message Monday morning saying that the speedo was not working!
I explained to her that it was because the speedo got its feed from an abs sensor.(I had not thought of that when I pulled the fuse)
She requested that I put the fuse back in when she got home.
I duly replaced the fuse and took it out for a spin - and it behaved perfectly normally under braking.
Manda has used the car today and again it has not done it once.
It is early days yet and I have no idea why leaving the abs off for 24 hrs should have had such effect.
Of course it could have been that some crud that had been causing the problem happened to coincidentally get dislodged. Time will tell.
The replacement hub nuts arrived today and I still intend to take a look at the backplate and clean it up but I am tempted to leave it a few days to see if the problem re occurs.
Could it be that the disconnect 'reset' the abs in some way?
It seems strange to me.

Brian

[Mike Noc]

Clear and concise photos as ever Steve.

Originally Posted by Arctic

2

Is this your car?

If so what is the state of the pipe under the rear seat that contains the fuel lines? On our car with the shorter metal cover in the wheel arch it is rotten, but on the longer cover cars no problem at all.

[Arctic]

Hi Brian
I would say it is more likely a bit of rust debris as fallen away from the magnet like you say, I doubt removing the fuse for 24hrs will have cured it.

Whip the disc drum and bearing and check the back plate, you may have got away with it, always best to make sure.

Mike yes that is my car, I have not checked under the seat but will take a look tomorrow and let you know

[brianw]

Originally Posted by Arctic

Hi Brian
I would say it is more likely a bit of rust debris as fallen away from the magnet like you say, I doubt removing the fuse for 24hrs will have cured it.

Whip the disc drum and bearing and check the back plate, you may have got away with it, always best to make sure.

I really cannot see that either.
Has Still not occurred again.
I will take a look though and give the backplates a go over with the rust killer paint, I forget the name but I have a tin I touched up the flaky bits on the arb, and rear suspension with.