Xantia: Reluctant ABS near stop

[svip]

We were replacing the ball bearings on my Xantia, because they were making noise. While we were down there, we decided to clean the ABS ring (if that's its name) around the shaft, because it was so rusty.

But then we noticed that when you braked, the ABS would suddenly stop braking just before stopping, before then braking again (what I call 'reluctant'). Giving one the impression that it was reading the ring wrong, and assuming the wheels were blocked, when they were not. Note: There is no problem at higher speeds.

We have now replaced the rings on both front wheels, yet the problem persists. The ABS lamp is not lit, but I haven't had a chance to see what Lexia says yet. But since there is no light, I doubt Lexia has much else to tell.

Does anyone have any idea what's going on?

[CitroJim]

This problem often happens if the ABS sensor is too far away from the ring...

This can happen if the sensor is removed and not correctly replaced - it is easy to get it wrong

The gap between the end of the sensor and the ring must be very small and no more than 1mm

I am guessing you removed them when replacing the bearings?

[svip]

The good news is that it's now working again.

It turns out, as you said, the distance was the problem. The weird part was that the new sensor we tried did not work at all, and I also noticed its magnet was less strong than the original one. So we put the old sensor back on, and now it's working. We were first concerned, because we had the Lexia plugged in while we were driving, and the ABS-light stayed on. But it turns out, this was because we had the Lexia attached. As soon as the laptop ran out of battery (very old one), the light turned off. Lexia also reported no faults and the ABS behaved as expected.

[CitroJim]

Excellent Very pleased indeed!

Good job it's fixed as ABS faults like that can be at best unnerving and at worst downright dangerous... If it happens, I believe it's best to disable the ABS until fixed...

[ekjdm14]

+1 on disabling it in these situations, one of those rare ABS faults that doesn't register as such and disable it for you.

I find ABS a mixed blessing on occasion, 99% of the time it is beneficial but I have experienced ( in a heavy RWD car) moments where I would have been better off locking the wheels on purpose thus continuing on my slide rather than the ABS kicking in and allowing the car to spear off towards the inside of the curve. Also on snow or loose surfaces I like to be able to choose if/ when I lock 'em up.

Very rare circumstances though, the rest of the time it's a great system.

[CitroJim]

Very rare circumstances though, the rest of the time it's a great system.

Agreed wholeheartedly...

I have a very rare Xantia without ABS. I always have to be conscious of that as if there was ever a car that needs ABS it's a Xantia.

[Jaf]

I don't have abs. That's the system that stops skidding? It's fun on the rambla (dirt track) as with the lively rear I can slide round the corners but if I have to brake it all gets a bit "eerk".

[ekjdm14]

Very rare circumstances though, the rest of the time it's a great system.

Agreed wholeheartedly...

I have a very rare Xantia without ABS. I always have to be conscious of that as if there was ever a car that needs ABS it's a Xantia.

As do I, I think. Will have to be careful with that lol

[Stickyfinger]

Wimps...... you can use it a a "limit" indicator

[CitroJim]

Wimps...... you can use it a a "limit" indicator

I've had experience of a Xantia with duff ABS and a four wheel lock-up under emergency braking Alasdair...

A bit of a brown trousers moment but to the car's credit it handled it bloody well...

I've also had experience of an Activa with duff roll correction but that's another story and another pair of brown trousers

[Stickyfinger]

I am looking forwards to expecting it to, then it deciding not to do it

[CitroJim]

I am looking forwards to expecting it to, then it deciding not to do it

I'd not look forward to it Alasdair - it's scary when it happens...

I almost ended up in a ditch as a result...

[svip]

I thought I had it fixed, but it happened again. I am now considering disabling the ABS until I've probably fixed it.

But so far, it has only happened once. I worry it might happen another time, where it could be more dangerous. But it's always just near stopping. In this case, I was trying to park.

I have to ask then, how close should the sensor be to the ring?

[Hell Razor5543]

Close. I have heard of occasions when somebody has replaced a failed sensor only for them to have similar problems to yourself. It turned out they had fitted the heat-shield between the sensor and the hub, which caused poor readings of the reluctor ring (as the sensor head was too far away to read the magnetic distortion). When they refitted (so it went bolt head/shield/sensor/hub) the ABS started working properly.

[svip]

Dang. We did head/sensor/shield/hub. I guess we now know how to fix it!