Removing rear ABS sensor on a Xantia

Neil Taylor · Post by **Neil Taylor** » 20 Jul 2006, 20:19

Does anyone have a good procedure for getting these rather fragile looking sensors off the rear of a 94 Xantia 1.9TD hatchback?

I've struggled with loads of pernetrating oil and hammering with wedges between the little heatguard backplate and the casting it is mounted to, but to no avail. The backplate is lose, but the unit refuses to free up in the hole. It doesn't look as if it will stand much physical abuse and I'd rather not wreck it if I can avoid it.

Alternatively if this is necessarily risky for the unit, how much of a pain is diconnecting the wiring as an alternative?

Third option: Is it reasonably possible to remove the rear trailing arm anyway, and replace the bearings in situ with the ABS unit still attached?

Many thanks,

Neil Taylor in Milton Keynes, England

slim123 · Post by **slim123** » 20 Jul 2006, 23:07

Easiest to remove the sensor whilst the arm is still on the car, this way the arm is held still.

You need a medium sized hammer and a long punch / drift.

After soaking the sensor in WD40 type lube, give the metal surround some good hard whacks using the hammer and punch, this will shake the corrosion.

Next working one side then the next, you will need to GENTLY tap the side of the sensor, to do this you will dent the heat shield badly, but this can be hammered flat again when off.

The rule is GENTLY does it, as you tap either side backwards, the sensor will rock, slowly it should start moving, dont get greedy and hit it too hard, as it will break, keep on spraying and tapping.

I have in the past removed loads of these in order to change the rear arms and very rarely broken one, but bear in mind I have taken up to an hour of gentle persuasion to succeed, still there is a chance that it will break!!!

When replacing, dont forget to paste some grease around the sensor, then next time it will pull out easy.

Good luck!!

The other thought is, when the arm is off, have a look at the bearings, the chances are that they have chewed up the housing of the arm ( they normally do) you would probabaly be better off fitting a re-con arm.

Regards
Slim

Neil Taylor · Post by **Neil Taylor** » 20 Jul 2006, 23:23

Thanks Slim for such an encouraging and prompt reply, I've got it soaking overnight in WD40 and will have another go tomorrow with renewed faith in patience!

I have a scrap yard that specialises in French cars who say they can supply arms at £35 each if it turns out that I need them, so I will be careful to ensure they are completely sound.

alan s · Post by **alan s** » 21 Jul 2006, 01:46

If it's any help.
WD40 has one problem when it comes to freeing rusted parts and that is it's very thin and can tend to evaporate before it's really sunk in to do the job. An old trick I've used for years is to firstly try the WD and if no luck, then use a bit of kerosene (I think you may refer to it as parrafin over your way) and mix this with an equal amount of engine oil.
If that doesn't do the trick, then either iuse straight oil or increase the % of oil in the mix. Regardless of how rusted it is, oil will eventually soften it enough to crack it free.
Slim is spot on with removal procedure.

Alan S

citronut · Post by **citronut** » 21 Jul 2006, 08:44

in your attempt to remove it you have probably damaged it allready,there is no need to remve it from the arm when doing arm bearings you just unplug the wire and leave the sensor in place,the reason they get stuck is the hub is cast iron which corodes and bittes into the plastic body of the sensor,so usualy you can not get them out in one piece or you brake the cast iron in the proces
regards malcolm

Neil Taylor · Post by **Neil Taylor** » 21 Jul 2006, 09:55

I like the sound of unplugging the wire Citronut as if I don't have to remove something so easily damaged obviously it would be preferable to be able to leave it in peace.

Where exactly do you disconnect the wire, I can barely trace its course?

citronut · Post by **citronut** » 21 Jul 2006, 12:45

the plug conecters for the rear ABS sensors are one on top of each subframe side rail,if you put your fingers over the top side sections of the rear subframe run them along you will find the conecter,they are very tight for space but you can just about get to them,i hope you have not knackerd your sensors yet
regards malcolm

Neil Taylor · Post by **Neil Taylor** » 21 Jul 2006, 13:28

Slim, I've followed your suggestions, but it ain't working, so perhaps I'm not fully understanding your technique, or how this thing comes apart.

slim123 wrote:Easiest to remove the sensor whilst the arm is still on the car, this way the arm is held still.

You need a medium sized hammer and a long punch / drift.

After soaking the sensor in WD40 type lube, give the metal surround some good hard whacks using the hammer and punch, this will shake the corrosion.

Done well over an hour a side over 2 days now. I assume you mean hammering the cast iron mounting for the sensor assembly?

slim123 wrote:Next working one side then the next, you will need to GENTLY tap the side of the sensor, to do this you will dent the heat shield badly, but this can be hammered flat again when off.

Can you expand on this because this might be where I'm not understanding you? I've been tapping the shiny metal cyclinder that encases the black square section plastic sensor with a piece of pine in between it and the hammer in order not to deform the metal too badly. This is now somewhat rippled anyway despite taking this care. I have also been hitting the assembly at its central point from the top at the back (inside).

The only movement achieved has been to get a slight back and forth turn on the black square section within the shiny outer tube by tapping the assembly from the back and down from the top at either end. Is this how the unit is supposed to come free, by forcing the sensor back inside the shiny outer tube, leaving that behind in the casting? Your next para would seem to confirm this idea?

slim123 wrote:The rule is GENTLY does it, as you tap either side backwards, the sensor will rock, slowly it should start moving, dont get greedy and hit it too hard, as it will break, keep on spraying and tapping.

I have, and for at least 2 hours on the one side, but there is absolutely no sign of movement on the silver outer cylinder, keeping it all constantly wet with WD40, and frequently also hitting the casting as hard as I dare.

It's looking as if we may be without this car for longer than we had hoped and run into the wrong side of the weekend for buying arms if/when discovered necessary.

slim123 wrote:I have in the past removed loads of these in order to change the rear arms and very rarely broken one, but bear in mind I have taken up to an hour of gentle persuasion to succeed, still there is a chance that it will break!!!

I think/hope they're just bruised rather than broken so far.

slim123 wrote:When replacing, dont forget to paste some grease around the sensor, then next time it will pull out easy.

I will, but at this rate there ain't goin' to be a next time!

If you can put me straight on whether I'm supposed to be removing the sensor from the tube, or the whole tube from the casting I would be most grateful, thanks.

Neil Taylor · Post by **Neil Taylor** » 21 Jul 2006, 13:46

alan s wrote:If it's any help.
WD40 has one problem when it comes to freeing rusted parts and that is it's very thin and can tend to evaporate before it's really sunk in to do the job. An old trick I've used for years is to firstly try the WD and if no luck, then use a bit of kerosene (I think you may refer to it as parrafin over your way) and mix this with an equal amount of engine oil.
If that doesn't do the trick, then either iuse straight oil or increase the % of oil in the mix. Regardless of how rusted it is, oil will eventually soften it enough to crack it free.
Slim is spot on with removal procedure.

Alan S

I used such a mix as a spray underneath a Triumph Herald for 13 years, selling it in excellent bodily condition at 19 years! so I know how good it is at penetrating. It worked its way through every seam and ended rusting completely. I'll try this now since I seem to have run into a wall with keeping up the WD40, thanks.

citronut · Post by **citronut** » 21 Jul 2006, 17:49

if the square section is moving seperatly from the round body that sensor will be shot,so you might as well buy a new one and smash the old one out,you should not wrench or hit these,and also do not hit the cast iron section it passes through or you could end up serching for a complete second hand arm
regards malcolm

slim123 · Post by **slim123** » 21 Jul 2006, 18:00

The arm is not cast iron, it is a drop forging, this will take a lot of beatings without breaking.

Tapping around has allways worked for me, if I can I will sort out a photo so that it can be seen as I an not too good at explaining with words.

Regards
Slim

citronut · Post by **citronut** » 21 Jul 2006, 18:25

slim123 wrote:The arm is not cast iron, it is a drop forging, this will take a lot of beatings without breaking.

Tapping around has allways worked for me, if I can I will sort out a photo so that it can be seen as I an not too good at explaining with words.

Regards
Slim

this may be so but i have seen someone brake one of these lugs off whilst trying to remove a sensor,also it dont get away from the fact that there is a 99% percent chance this sensor is shot
regards malcolm

Neil Taylor · Post by **Neil Taylor** » 21 Jul 2006, 18:38

citronut wrote:if the square section is moving seperatly from the round body that sensor will be shot,so you might as well buy a new one and smash the old one out,you should not wrench or hit these,and also do not hit the cast iron section it passes through or you could end up serching for a complete second hand arm
regards malcolm

Then you seem to be saying in effect that these sensors cannot be removed without destroying them, and yet Slim has apparently managed this on many and most occasions using hitting and tapping you say will destroy it? I feel increasingly despairing between the two advices, and my failure to shift the wretched things, and from the reported price of them, I'm not buying new ones. The whole cost just escalates too high for the value of the car. They seem ruthlessly intended to be just thrown away.

As for needing a new arm, it seems from reading here, and from knowing how long this lean in on the back wheels has been present that there is a strong chance the arms are knackered anyway. However what my chances of obtaining second hand arms with sensors from a yard without the wiring having just been snipped through I don't know. I'll ask tomorrow.

Has anyone ever made a successful join in these wires?

The movement of the square sensor in its casing is very slight, maybe one degree of turn, and seemed to be there from the outset. it's certainly not hard to believe in destroying them though.

Perhaps a simple circuit to light the ABS light, then put it out, and a complete disconnect of the ABS might fool the MOT. I've never had ABS before, I've never evoked its operation, and I couldn't care less about having it anyway, but its killing the whole car!

Neil Taylor · Post by **Neil Taylor** » 21 Jul 2006, 18:49

slim123 wrote:The arm is not cast iron, it is a drop forging, this will take a lot of beatings without breaking.

Tapping around has allways worked for me, if I can I will sort out a photo so that it can be seen as I an not too good at explaining with words.

Regards
Slim

LOL, they say a picture is worth a thousand words, and I sympathise with the difficulty in describing in words how to do this. Clearly it is possible to break the castings, and maybe I've been too gentle with hitting it so far. It is probably impossible to convey successfully the force needed, but I haven't broken the castings so far, and think I have a feeling for what's sensible.

I've employed Alan's advice about the paraffin/oil mix, so since I'm now unlikely to obtain replacement arms before the w/e, I may as well let it stew in that mix for the next couple of days and have another go at it.

I'm still assuming, and from the Haynes pictures that I have, that the silver cylinder has to be withdrawn from the casting, not the black square section sensor from the silver cylinder?

citronut · Post by **citronut** » 21 Jul 2006, 18:59

im sorry if my advise is give you probs,but i would not sudgest removing these sensors when just replacing arm bearings,also if you went to the breakers you could remove the arms yourself and keep the wire intact,even then you may need to fit new beariongs to these arms,where did you get a price from as GSF PART No.N64516 PRICE £52.20+vat
regards malcolm