brake judder air?

[VertVega]

OK John, that was what I've also suspected.

You should now check the heat shield of the front wheels.
Heat shield looks like a "bumerang" (a bad designed one)
The bolt which tightens the ABS sensor should be fixed in the same way in both front hubs.
If the heat shield (thickness ~1 mm) goes under the ABS sensor body on one side and the other way on the other side
then this will cause air gap (toothed ring <--> sensor) difference.
As a result the brakes will kick back in a strange manner, at low speed, almost just before complete stop.

Above is based on a true story

[John Plum]

Inspired by you VertVega, I pulled out Fuse no. 1 in the engine bay for ABS, and the symptoms dissapear. Lovely!

What does that imply?
Any more advice most welcome, it's almost all sorted.
The warped disc, and the duff accumulators had to be replaced, as well as LHM, in this newly acquired vehicle, so all the work so far has been all good. It made sense to put in new brake hoses at the same time.

[VertVega]

I pulled out Fuse no. 1 in the engine bay for ABS, ...

Then you'll not have ABS and that wouldn't pass MOT

Since the symptoms were similar I thought it was the heat shield assembly which caused this problem, like in mine
I don't remember now which one is the correct sequence but on one side it was fixed as:
Hub, sensor, shield and bolt (other side like hub, shield, sensor and bolt). You've checked them already.

Next you can check the toothed ring condition and the sensor tip if they look clean and no missing parts.
Using your camera you can compare the air gap on both sides.

Sorry, can't find anything more.

[John Plum]

Hub, sensor, shield and bolt

That's the order of both of mine. I'll check it against a diagram.
In addition I'll check the gaps and shim them to 5 mm gap, as well as reclean them, and measure resistance. Cheers Vertvega.

Update: Haynes strip down confirms the order: sensor, sheild , bolt,

[John Plum]

Hey Hey: I couldn't wait, So I filed down my meters' probes to get contact with the ABS ECU connector and took resistance readings with one zero in the result:
FR zero
RR 1069
RL 1075
FL 1079

The problem solving is going well.

[VertVega]

That's "good news" . So you'll seek for a new one in eBay .

If you insert the ABS fuse than the dashboard ABS light should stay on.
Another point, before removing (or throwing away) the sensor you can measure from the sensor connector (see pic).

I have sent this picture before in another thread. It is from front left side.
Right side is "almost" mirror image of this .



PS: my meter shows value 1 for open circuit. may be different standards(?)
Value "1" (on the left most side) is also seen when meter is switched to Resistance mode.
Touching probes to each other, display value settles down to "000".

[John Plum]

Hi Vertvega,
Yes, it's good news.
I can confirm the abs dash-light comes on with fault testing, and then goes out. My meter show s 0.L for open circuit, 0.0 for touching probes; that's its military convention. You were sharp to notice; yes I could have said 0.L (= open circuit).
I'm definitely going to measure the sensor at the connector first thing am., and clean it again before getting a new one, if required.

It was amazing to drive the car without any problems , very motivating, and its great to think we might have this well and truly nailed, and well set up. At times I have felt a little . It's also great to think that everything will have been sorted that needs to , even that with the cold weather, I shall have a blower motor under control, thanks to Jim's speed regulator repair.

[CitroJim]

Good, pleased the root cause has been found John. It is worrying that the ABS light is not giving the correct indication though as it should be glowing like a beacon with one sensor open circuit

You'll need to Lexiate your ABS ECU in due course and see if it throws up any clues as to why. Get that MOT passed and pay me a visit!

I've heard of ABS lights being cross wired to the ignition or oil light to disguise a fault.

[John Plum]

it is worrying that the ABS light is not giving the correct indication though as it should be glowing like a beacon with one sensor open circuit

You'll need to Lexiate your ABS ECU in due course and see if it throws up any clues as to why. Get that MOT passed and pay me a visit!

Agreed! I'm very keen to do the Lexiation after the MOT, and would love to pay you a visit.

[John Plum]

With some continuity and resistance tests:

• RH sensor, tested from its end junction gives correct resistance: sensor in fact should work.
  Pin no 1 (red) of the ABS ECU connector to the sensor terminal block has a break.

I looked at the wiring under the car. I've decided I will go for a extra wire spliced to the ECU connector red wire (to terminal 1) somehow. I'll assume the break is close to/at the terminal block. If you have any experience of this fix, I'd be grateful for a tip. Thanks,
John

[CitroJim]

More than likely caused by a chafe on the loom John.

I'd avoid breaking into the ABS ECU connector if at all possible.

If it will help, I can supply you the applicable loom (harness) diagrams which show the physical layout and routing of the loom in question. The don't always run as logically as you may think

I can's supply the diagrams until later this evening...

[John Plum]

All may be well with the loom, then after all. I got a continuity and a correct sensor resistance on the RH from the ecu connector, after further cleaning the male sensor terminals with a file and alcohol.

Cleaning and reassembling the sensor bolt area and the sensor itself must have helped, because when I put the wheel on and drove the symptoms had disappeared BUT now tha abs warning light stays on!

Now I'm totally baffled. Time for a lexia reading maybe, I think!

[John Plum]

OK. 8) Found the fault with the ABS warning light: the RH ABS cog is broken. (I hadn't dismantled that hub to derust the cog, only a superficial clean and inspection before). Upon further cleaning, and re-positioning of the broken cog, I got the light to go out, but I shall replace it if I can get one separately from a driveshaft. I hope so. (EDIT: No , not available seperate; found cv joint from JT Trading, Birmingham £25.00 inc boot kit, and delivery).

The strange thing about all the ABS fault reports is, initially on the LS a dirty sensor head caused a warning light, which then disappeared upon cleaning. Cleaning the RS terminal block/sensor seating and head brought the light back on where there was an unseated/ broken ring. I had assumed that there was no further ABS fault, until after the air/hydraulic braking problems were taken care of.

After a short drive, The ABS ring is still holding it's position - no fault light, although its split. I'm tempted to take it to the MOT tomorrow morning, as the CV joint won't arrive until next week, and I have to find time to swap it over. VERY tempted

[citronut]

i have just cleaned these up and re/welded them back in place before,

so if you have got a mig or know someone localy try that before spending your dopsh on a new CV jooint,

it is posible to do it in situe

regards malcolm

[John Plum]

i have just cleaned these up and re/welded them back in place before

Great Idea Malcom! I prefer it. I went ahead and ordered a new CV joint though. Well, anyway this one is pretty bad, tooth missing where split: doesn't trigger a warning though.


Problem solved I think! Hooray! Yipee!

So nice to drive now.