Hi, I wonder if anyone might be able to offer me some advice.
Despite having liked Citroens for quite some time (my favourite car as a child quite bizarrely being the XM), I have only recently ventured into the world of citroen ownership, with a 2000 Xantia 1.8 16v petrol in LX trim - I would have prefered a diesel but the petrol model that I came across and subsequently bought was a steal - and in fantastic condition.
I have owned the car for maybe a month now, in which time I have noticed very little in the way of problems, apart from a very intermittent problem with the brakes. Every now and again, perhaps once a day on the 20 (town) miles that the car is driven, the brake pedal will pulsate (almost as if it is ABS acting under hard braking) even under only the slightest application - sometimes when slowing down for traffic lights from as little as 10-15 mph. This is very sporadic; 95% of the time the brakes are very taut and feel almost as new - but every now and again when braking the pedal jerks and shudders under my foot, accompanied with a very clunky sound and not a lot in the way of actual braking happening! This has happened once at speed, approaching a roundabout at approximately 40mph, and I only just managed to stop in time (engine braking in second gear) - understandably I am quite worried about it!
Since owning the car I have replaced the accumulator sphere - more to do with the fact that it was flat - this resulted in, if anything, the brakes feeling more taut when they work - but still with the intemittent shuddering.
I hope I have explained myself well enough - does anyone have any ideas?
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Best get the codes read to see if any faults are logged but as it's a brake issue better to get it done now.
Im thinking Abs related, as opposed to the normal brake disc warped etc.
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Yes, it does sound like an over enthusiastic ABS system, if you know anyone else with a similar car see if you can borrow an ABS ECU to try in yours, or you could probably pick one up from a scrapper for not to much money.
I have been running XMs for about 13 years now, I have three at present - best car in the world.
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Thanks very much to both of you for the input - I appreciate it.
If I am to get a new/second hand scrapper ABS ECU, is this an easy change for me to do DIY (average mechanical knowledge)?
Is it more likely to be the ECU or the sensors feeding it?
Thanks again, I really appreciate it...
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Normally just plugs in peter will be along soon to advise as he drives one.
But yes do try it otherwise you will have to get the codes read but unplugging it may wipe the stored codes.
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Thanks BigTee and Peter.
Any help on changing the ECU would be greatly appreciated (including where it is - I have no haynes as of yet!) - with the new accumulator in, this is the final thing before the car is 100% spot on!
Thanks again...
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In fact, a thought has just occured - if I have a 2000 Xantia in forte (lx) trim, 1.8 16v - does my car actually have ABS?
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Have a look under the bonnet.
I'm not used to Citroens, but every other car I've seen with ABS has the brake lines all going to a sort of big junction box.
Altenatively, take a front wheel off and see if you've a sensor close to a cogged ring, usually on the CV.
It should also have an ABS warning light which illuminates for a short while during ignition turn-on. This is an MOT check item I believe.
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A 2000 reg Xantia will have abs.
The abs ecu is in front of the battery and behind the headlight. There is a black multiway connector plugged into it on the side nearest the inner wing.
It is worth unplugging the 2 abs fuses and trying the car to see if the shuddering disappears. Remember you won't have abs! If it doesn't it may be a suspension joint.
On that year Xantia the abs ecu is very reliable, the wheel sensors are more likely to be the problem.
Can I suggest that you visit www.frenchcarforum.co.uk ? There's loads of information and Xantia experts on there.
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Unlikely to be the ECU - much more likely to be a clagged up or broken ABS ring on the front. Jack it up and look carefully at each of the ABS rings, looking for cracks in the ring. The rings can be replaced separately from the CV joints fortunately!
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Thanks very much for the advice - looked at some info on ABS rings and the symptoms certainly sound similar to what I am encountering - but if the ring was faulty/cracked, would this not create a constant problem, as in cause the shudder every time I brake, as opposed to the sporadic problem i am facing?
Thanks very much in advance everyone...
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Had this exactly as you describe on a Citroen ZX and it was cured by removing the driveshafts and cleaning up (wire brush and file) the abs rings which had lost their *tooth* profile due to corrosion building up in between the peaks.
Also make sure you don't have an odd size tyre.
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The reason for the abs coming on at low speeds is that the amplitude and frequency of the signal from the wheel sensors decreases as the wheel slows down. It is the frequency of the signal that the controller is measuring, but, if the signal amplitude is marginally lower from a wheel due to a cracked reluctor ring, damaged teeth, or crud it will be unable to measure it as you come to a standstill and apply the abs.
This will also increase your last few feet of braking!
I suspect one of the signals is marginal, causing the intermittant operation.
On my Xantia I only ever had problems with the front sensors, keep us posted!
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Thanks very much for all the help so far, I really appreciate it. Am pretty convinced that the reluctor rings are the cause for the fault here, and I am going to tackle the job tomorrow...but prior to that...what M.M said about different sized wheels raised a thought...I have a slow puncture on the front drivers side-will be getting changed come pay day-I inflate it approx twice a week - when the tyre is underinflated, could this fool the ABS system in to thinking that the front wheels are travelling at different speeds? Just a though before I start getting down and dirty with the Reluctor Rings...
Thanks again for all advice so far...
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Have you a same sized spare you could swap on to see if it stops the problem?
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Unless you are letting the tyre go flat and running on the rim, I doubt a slow puncture will cause the problem. The ABS system has to cope with the different wheel speeds caused by cornering.
Before tackling the reluctor rings I would at least check the sensors for continuity at the multi plug on the side of the abs ecu.
LH front: Pins 1 and 2
LH rear: Pins 5 and 6
RH rear: Pins 22 and 23
RH front: Pins 19 and 20
The pin numbers will be seen if you look carefully at the plug base.
Check with the ignition off and the the multi plug unplugged. (Lift the red locking catch and the plug pulls off easily.
You should see a resistance of around 1000 to 1100 ohms across each pair.
It's worth having a look on the frenchcarforum as well. Changing the reluctor rings means taking the hub off, not difficult but I'd do the easier checks first.
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