Xantia 2.0HDI brakes

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Tony589
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Xantia 2.0HDI brakes

Post by Tony589 »

Hello,
After MOT tester changed outer CV joints and lower arms, my brakes arre behaving strangely.
Under light braking there seems to be no braking effort and I can feel the ABS solenoids pulsating at the pedal, when the pedal is pressed harder the brakes are suddenly applied VERY hard.
My first thought was contamination on discs, but then the ABS light came on and the brakes worked normally. It seems the problem is with the ABS.
The ABS light now sometimes stays on and the brakes work OK, but sometimes it clears OK and the brakes are dodgy.
I have taken the car back to the garage and asked him to check the number of teeth on the reluctor ring and check for damage to the sensors.
Any other suggestions?
Thanks,
Tony.
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Re: Xantia 2.0HDI brakes

Post by CitroJim »

Tony, this is a common'ish problem and is caused by the ABS sensors being incorrectly fitted in the hubs and usually because the tip of the sensor is too far away from the 'dragon's teeth' of the reluctor rings. Looks like your garage may have incorrectly fitted them and commonly they place the heatshield tab below rather than above the ABS sensor boss.

The tip needs to be surprisingly close. the strange effects you see are caused by the signal from the sensor being too weak at low speeds to properly signal the ABS ECU.

Else that or the new outer CV joint reluctor rings have the wrong tooth count on them. More likely to be the first problem though...
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Re: Xantia 2.0HDI brakes

Post by Tony589 »

Thanks for the reply Jim.
Called in at garage after work and they had it up on ramp bleeding the calipers.
I told them of your ideas , they had already counted the teeth and they were correct, so we got below to look at the sensor.
It was the mechanic who noticed it, the reluctor ring on the new CV joint did not line up with the sensor! About 50% of the tooth was being sensed.
This presumably accounts for the weak signal as you suggested.
I am taking it back in the morning, they are going to remove the CV joint and compare it to my old unit before contacting their supplier.

Bit of drama when I took it home, brakes were working fine till I pulled up outside home then no brakes at all!!!! nearly hit the car parked in front.
I lifted the bonnet and disconnected the ECU plug on the ABS unit, I'd rather not have ABS at the moment.

I will report any findings tomorrow.

Thanks for the help.

Tony.
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Re: Xantia 2.0HDI brakes

Post by CitroJim »

The sensor not lining up with the reluctor may not be the full problem Tony. I must confess in replacing reluctor rings I managed to get them out of alignment, I'd say about 60 - 70% were over the sensor tip, and it made no difference as James (HellRazor) will confirm... We looked at the sensor output on diagnostics turning the wheels very slowly to confirm the sensors were giving a signal of sufficient amplitude to keep the ABS ECU happy...

I'm not saying categorically that mis-alignment does not matter, just relating my personal experience of it and that some is certainly tolerable.

If your garage has Citroen diagnostics (Lexia or ELIT) then they can look at the sensor signals at low rotational speeds and see if the ECU is reading them correctly.

I can imagine all loss of brakes was somewhat hairy. Good idea to leave the ABS disabled until this is resolved and here's hoping the mis-alignment is enough to cause the problem and getting the rings in the right place will resolve it.

The rings are heat-shrunk on. If push comes to shove the garage may be able to very carefully heat them and move them into correct alignment.
Jim

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Re: Xantia 2.0HDI brakes

Post by Hell Razor5543 »

I can confirm that, although the rings didn't quite line up (about 70% overlap, but this means about 30% adrift), when I headed for home the ABS was happy (up to a Sat Nav speed of a nice round multiple of 10MPH). Before that, at speeds of a bit over 70MPH, the ABS would get confused and take itself off-line.

According to other ABS threads I have read here, if the ABS detects a problem it (for a few seconds) disconnects all normal braking while it tries to work out what went wrong. As the problems are normally detected when braking, it does make for an interesting few moments while you pray and grab the handbrake. As CitroJim said, disconnecting the ABS is the best option. However, to prevent the connectors getting dirty (and possibly causing problems in the future), if your car is an S2 Xantia, Fuse 1 (20 amp) under the bonnet ONLY runs the ABS ECU (but PLEASE confirm this by looking in your car handbook, if you have one, or waiting for somebody else to confirm my findings), I'd be inclined to pull it and then re-seat the connector (after spraying both the cable connector and the ECU connector with a proper contact cleaner).
Last edited by Hell Razor5543 on 31 Jan 2013, 20:42, edited 1 time in total.
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Re: Xantia 2.0HDI brakes

Post by RichardW »

My guess is they've fitted a smaller diameter CV joint off an earlier car - this will definitely upset the ABS!
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Re: Xantia 2.0HDI brakes

Post by CitroJim »

RichardW wrote:My guess is they've fitted a smaller diameter CV joint off an earlier car - this will definitely upset the ABS!
Yes indeed! Good thinking Richard. I reiterate the gap between the tip of the sensor and the teeth of the reluctor is surprisingly small. I can't recall exactly now but less than an mm I'm sure... If you can see a large gap between tip and tooth then that will not help...
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Post by addo »

It's normally well under a mil. Gauge it with a business card folded in half.
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Re: Xantia 2.0HDI brakes

Post by RichardW »

Early ones are 80mm id, later ones 90mm, so the gap will have opened up to over 5mm if the wrong CV is fitted. They probably look very similar on a passing glance, but a measure will reveal. IIRC Kenny fitted a wrong one to his and had the same ABS trouble.
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Re: Xantia 2.0HDI brakes

Post by Tony589 »

Spoke to mechanic, he's taken one side off and compared with the old one.
He says there is about 1/8" difference, didnt say which dimension.
Nobody he's rung stocks them, Page's are trying to get us some for this afternoon.
Thanks for replies folks.

Tony.
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Re: Xantia 2.0HDI brakes

Post by Tony589 »

Car finally sorted.
Mechanic said they tried 6 sets of CV joints!
His supplier eventually had to drive to a place in Morley, taking one of my old units with him for comparison.
Once again thanks for all the help.
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Re: Xantia 2.0HDI brakes

Post by CitroJim »

That's good news Tony :-D Pleased we could help a little with this!
Tony589 wrote: Mechanic said they tried 6 sets of CV joints!
Gosh :shock:
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Re: Xantia 2.0HDI brakes

Post by Hell Razor5543 »

That sounds like a garage who is prepared to get the job done properly, and (if they are as good as they sound) will have learned from this experience. They listened to you, and didn't fob you off. If you are happy with the outcome and the service, it could be worth posting the in the Recommended Garage section.

The fact that they made a mistake at first shouldn't count against them. Everybody does make mistakes. Not everybody learns from them. It would appear that they did learn, and will have improved for that.
Last edited by Hell Razor5543 on 02 Feb 2013, 08:46, edited 1 time in total.
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Re: Xantia 2.0HDI brakes

Post by CitroJim »

Hell Razor5543 wrote: If you are happy with the outcome and the service, it could be worth posting the in the Recommended Garage section.
Absolutely, yes indeed :-D
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Re: Xantia 2.0HDI brakes

Post by neil123 »

"The fact that they made a mistake at first shouldn't count against them. Everybody does make mistakes. Not everybody learns from them. It would appear that they did learn, and will have improved for that."

On the other hand, the fact that they seem to have let him drive it home with known defective brakes would have put them sitting next to him at Crown Court if the worst had happened... that he's an MOT tester is bloody scary.

Not one for the good garage guide in my opinion!!
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