Xantia MK II - ABS Question

[lancia58]

Hi

I have a Xantia MK 2.0 16V automatic. I checked the ABS. I pressed the braking pedal hard. I could only feel that the front right brake is pressing/releasing the brake pads, it was very noticeable. I could not feel that with the left front caliper and the rear ones. I could also hear slight squeak from the front left tire. Does this mean that the other ones are not functioning or that the front right is not OK due the pronounced action of pressing/releasing the brake pads.

Thanks
Zohar

[Hell Razor5543]

The rear brakes don't apply much pressure unless there is a fair bit of weight in the back (this can cause problems at an MoT when the tester believes there isn't enough braking force applied). This is due to the way the hydro-pneumatic system works.

I cannot speak for the front brake (apparent) imbalance.

[lancia58]

Hi

Should the ABS action be very noticeable ?

Zohar

[Northern_Mike]

I don't believe it's very noticeable on any car other than at the pedal.

The squealing is quite normal. Don't forget that with ABS the wheel will momentarily lock and release. On certain surfaces this will squeal. If it was locked it'd be a long screech.

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[lancia58]

What can be the cause for imbalance ?

Zohar

[Northern_Mike]

Your weight on one side of the car probably... unless it's pulling to one side there probably isn't an imbalance. The side you're sat on will have slightly more load and take slightly more pressure to lock.

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[Northern_Mike]

If there is an imbalance, a sticking caliper is most likely.

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[citronut]

is it possible the front right=O/S/F was the only wheel not griping the tarmac????, with wheel spin

[lancia58]

Hi Malcolm

The ABS operation was only noticeable at the O/S/F wheel, although the car kept going straight and fully stopped fast ( I drove around 28 MPH ). When I say I felt the O/S/F wheel it was like “bang, bang, bang”. As the car kept going straight I think overall the ABS is OK , but I wonder why only from the O/S/F wheel I felt the “bang, bang, bang” ( I guess the brake pads were pressed released )

Thanks
Zohar

[Northern_Mike]

You probably just heard the ABS block at work rather than the brakes themselves.

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[Mandrake]

I wouldn't go looking for problems that don't exist

You'd be very lucky indeed if both front wheels tried to lock at exactly the same pedal pressure - for that to happen the tyres would need to be identical in tread and grip characteristics and equally inflated, the road surface would need to be giving identical grip to both tyres, (not a given by any means, certainly not in the wet) the brake calipers would both need to be equally free, the discs and pads would need to be well matched etc...

In short unless everything is perfectly balanced (both on AND off the car) one wheel will try to lock first and will trigger an ABS response while the other one may not. (Unless you press a lot harder) Part of the design principle of ABS is that it operates independently on left and right wheels (only at the front on older cars like Xantia's - the rears are modulated together for simplicity) because pulsing the wheel that is not locking up doesn't buy you anything.

Find a long straight, safe stretch of road with no other traffic on it. Try an emergency stop from 60mph / 100kph - if the car pulls up straight, quickly, without locking any wheels or pulling to the side then your brakes and ABS are both working fine. Don't try to over analyse any noises that you hear - you might just have loose pads in one caliper (missing anti-rattle spring) that chatter slightly when being pulsed rapidly, or it could be the ABS block noise as Mike suggests. Neither is cause for concern.

[lancia58]

Hi Simon

Thanks BTW what is this anti-rattle spring ? Can you provide any picture ? I tried to look for it on the Citroen service but didn't find it . If you know the Citroen part number can you please post it. I had a very interesting ABS problem in the past that I want to share with the forum members, so here is the problem and the solution. When I drove slow ( 10 KPH ) and turned to the left while braking sometimes I lost the brakes i.e. no braking, I have to press again the pedal to stop. To track it down I removed the ABS fuse ( by that neutralized the ABS system ) and the problem disappeared. Now I knew that something is wrong with the ABS system. First I checked the front ABS sensors resistance while rotating the steering wheel left and right ( check if the sensors wires are broken) and both sensors resistance were OK and stable. I went to a local garage and lift the car, after a while I noticed that the right the shield is on top of the sensor where is the left sensor was on top of its shield. The outcome was that the right sensor was closer to the ABS ring by 1.5 millimeter in compare to the left sensor. When turning to the left the right wheel spins a bit faster than the left wheel which at low speeds cause the ABS computer to release the brakes ( scary feeling). After assemble the right shield on top of the ABS sensor the problem disappears

Thanks for your help
Zohar

[citronut]

here is price and part No. for the caliper spring kit from service citroen

Part Number Description Quantity Price excl. VAT Price incl. VAT Total incl. VAT Selection
95667820 PAD SPRING KIT 45.35 GBP 54.42 GBP 54.42 GBP

i didnt check if there are different ones for different model XANTS

but the spring is the stainless steel plate in the center of the front of the caliper,

they only show it in the kit above