Xantia Brake problem

[Hurdsey]

Thanks again guys, I know I'm asking loads of dumb questions, but I dont want to get everything jacked up and halfway through the job and find I need something that I cant get til' Monday.
I'm a Joiner so I've got a good selection of Screwdrivers of all shapes and sizes 8) So I should manage, also I've got the correct tool for doing this same job on a Sierra caliper thats fitted to my Westfield, you have to turn and keep the pressure on at the same time, It's to do with the self adjusting mechanism, I might be able to adapt this with a bit of luck

Paul

[paulbx]

I noted your test for rear brakes was to sue the handdbrake - this is a Citroen remember!


PaulB

[Hurdsey]

No that was my test for the front brakes, cos' thats where the judder seems to come from

[citronut]

probably 1/4 of an innch square,and it is turn and push at the same time usualy,unless your calipers are in very good condition then you can sometimes turn them with your fingers
regards malcolm

[Peter.N.]

Something that will fit across the piston and into the slots either side. You can do it with a flat bladed screwdriver but it takes an age. You will see what I mean when you do it.

[Hurdsey]

Mornin' Guys, Good news and bad, first the good.
My Sierra caliper tool just about fits the Xantia calipers, so that made that job dead easy

Next I replaced the front pads, the old ones on the offside were only about 40% worn and nice and even wear.
On the nearside the inboard pads were tapered from 10mm to 6mm and the outboard pad was tapered from about 2mm to 4mm, there was no other evidence of a sticking caliper or piston but I cleaned them both up and made sure everything was working smoothly, I know sometimes the leading edge wears more than the trailing one, but not in this case, I then put it all back together and bled the brakes, there was no air coming out but I only put about half a litre through cos' that was all I had to hand, the rear pads looked fine but the discs were quite rusty round the rim and in the centre (so I might replace them both next weekend). The thing is the pulsing problem is still there, I still feel it's ABS related, but it could be the Hydraulics, I'm thinking about a visit to Westroen for a new set of spheres, I assume when they fit them they replace the LHM fluid? anyone any experience of their service (they are quite local for me) and anyone got any other ideas about how to cure this scary problem, last resort would be replacing the front calipers, the discs were new 13,000 miles ago, and look ok, what do you think?

Paul

[jeremy]

Have a very good look at the caliper with the wedged pads. Its possible that there is corrosion between the caliper and the hub carrier (ie under the securing bolts) or another problem here that is causing the caliper not to sit straight. If its that - the corrosion can be ground off - and some grease or paint may stop it returning.

The other possibility is that the bearings between the caliper and the slide rod are worn allowing it to shake around. Give it a good shake without any pads in it - it should slide freely but be tight when shaken. New bearings may be obtainable but a recon caliper may be a better answer.

Sphere replacement doesn't normally involve more than a top up of the LHM.

Have you tested the accumulator? (run engine - car at normal height for a couple of minutes - switch off engine and sit in the boot. Car should sink and rise again after 30 seconds.)

[Hurdsey]

Thanks for the quick reply Jeremy, I also suspect that caliper, but if I yank on the handbrake the car stops as it should without any shudder or clunking iyswim it just feels nice and smooth.

I did take off the carrier and gave it a good wire brushing on the mouting faces.

I did the sit in the boot test but I'm only 10 stone so me and the wife did it together The car did settle down a bit and rise again, but didnt seem to move after we got off, (ooh err missus) dont forget this a later model with Anti sink, would this make a difference?

Paul

Edited to add

The nearside caliper was replaced under warranty by Citroen about 3 1/2 years ago.

[jeremy]

Boot test should work with 10 stone! My BX TD Estate will rise while I fill it with diesel!

If functioning correctly the back suspension on these cars is incredibly soft and it will go down a very long way. If it doesn't go down - the rear spheres are suspect. (should be the same with the engine running) The height corrector will return it to its original height but there is a delay built into it to prevent overcorrection during driving.

I think the anti-sink valve shuts if the regulator/accumulator pressure drops below that in the rear suspension - so no pressure there would shut the anti-sink valve. Basically if it does the same with the engine running or not the accumulator is OK, if its different the accumulator is not.

Another test is to raise the car fully and see if the ticking rate decreases - as all the spheres (or most) are now functioning as accumulators.

A healthy car should not tick at more than about 30 second intervals after its settled down at running height. If it ticks mere often it's not necessarily the accumulator, but if its 10 seconds or less it probably is.

[Hurdsey]

Morning Guys, I'm on a steep learning curve on Citroen hydraulics, please be patient with me.

I've finally got hold of a Haynes manual for a Xantia, They dont do one for the HDI model but I assume most of the other mechanicals are similar, one difference I've noticed allready is the brake caliper is held at the bottom by a bolt instead of a pin and split pin, but thats not really a problem.

I've re read the thread completley, Malcolm yes sometimes it feels like the brakes are being released, but it's intermittent, 50% of the time the brakes work 'normal' sometimes it sort of 'clunks' which you can feel through the pedal, if I yank on the handbrake it stops smoothly and normally which to me seems to rule out caliper problems or warped discs, I know there is not as much pressure with the handbrake as the foot brake.

What is the accumalator shere? in the book there is nothing described as such, there is a hydraulic pump. a hydraulic pressure regulator and a brake control valve, is any of these the accumalator sphere?

There are 6 spheres on the supension if I have them replaced would that help the hydraulics to work properly on the brake side?

Loads of questions I know, but you guys out there have loads of knowledge of these things so I'm sure one of you can held somehow.
In 40 years of driving I have never experienced symptoms like these, must be something peculiar to Citroens that I am missing.

Paul

[jeremy]

Sounds like you need a good textbook on Citroens and hydraulics. Go to

http://www.tramontana.co.hu/citroen/ a ... adiator)

[Hurdsey]

Many thanks Jeremy, theres some heavy reading there
Guess what I'll be doing tonight

[jeremy]

Its good stuff - not sure if the Hydractive is quite the same fro Xantuia and XM for which its written - but the other bits are - and the differences may be electronic - but it would seem that your car doesn't have an electronic system anyway.

[Hurdsey]

I've booked the car in at Westroen for a new set of spheres this afternoon, I'm convinced It's ready for them now, That should eliminate one area, then leave me free to concentrate on the brakes at the weekend knowing that the acumulator sphere is ok.

[jgra1]

dont forget that little 'idiot spring' though Hurdsey.. mentioned early in the post

I have yet to do mine

John g