Xantia Brake Problem

Miker G · Post by **Miker G** » 18 Sep 2010, 15:09

Hi Everyone.
I have a 1.9tdi 97 plate xantia. Everything is great apart from the brakes.
When I come up to stop when I press the brake pedal it brakes normally but then it sorta slackens off so the car sorta lurches a little bit. It slackenes then tightens then slackens again all very quick.
Is it the brakes need bleeding of air or something as I saw something in the manual about that, any other ideas anyone?
thanks.

Old-Guy · Post by **Old-Guy** » 18 Sep 2010, 16:58

I suggest that for starters you:

1. Check the LHM fluid level (engine running, suspension on highest setting, wait for it to rise fully, the orange 'flying saucer' should be between the two marks. If necessary top up SLOWLY with the engine still running.

2. If the problem still persists, bleed the brakes, starting from the rear.
For detailed instructions read either Jim's sticky or my article on replacing spheres, changing LHM and bleeding barakes.

Post by **CitroJim** » 18 Sep 2010, 17:30

As Guy says, you'll likely find loads of air in the rears. Often as a result of a ruptured sphere.

Also check the accumulator is good. In fact both of them.

Listen for the regular tick from the pressure regulator. If the tick interval is less than 30s, the main accumulator is weak and needs to be replaced. Ideally, on a good system, the ticks should be a minute or so apart or even longer on a non-hydractive car such as yours.

If you have no history of replacing the rear "Anti Sink" sphere, do so as this is the rear brake accumulator. There is no easy way of testing it. This sphere is often overlooked as it seems to do nothing much and therefore can rupture unnoticed and fill the brake circuit with air.

Bleed the rears on high setting with weight on the opposite wheel.

HDI Dave · Post by **HDI Dave** » 18 Sep 2010, 20:43

Miker G wrote:
When I come up to stop when I press the brake pedal it brakes normally but then it sorta slackens off so the car sorta lurches a little bit. It slackenes then tightens then slackens again all very quick.

Ahh, glad you posted this,mine does the same,the brake pedal kind of pulses, so I'll be interested in a remedy

Not used to all this citroen malarky.Why have nearly everything all connected? so if you lose sufficient lhm the whole lot's nackered? I'd rather have a seperate hydraulic braking system...

Can air get stuck in the pipes near the lhm tank?
I ask because my pulsing problem started, I think, when we had the lhm tank off to do the clutch. Did we label the pipes? No,of course we didn't, they could be on the wrong way round for all I know, we just guessed

Any 'normal' car and it feels like warped disks !

I might have a bash at bleeding the, bleeding thing then and report back OP, to compare results

Quick sidenote,
after my lhm tank/res was plumbed back in, we refilled it to the mark,between the red? lines,engine running etc,or however it's done..but it keeps spitting some green lifeblood out. I topped it up a few times but it keeps doing it..is this normal? I thought it might be the citrobics exercise I've been doing,(the front seems to be sticking..) There's a constant puddle of lhm on the top of the tank..I got bored of mopping it up

As above,air in the pipes near the lhm reservoir or the brake system in general?

the_weaver · Post by **the_weaver** » 18 Sep 2010, 22:19

I had a pulsing brake pedal on my ZX, and I thought it felt like warped discs. It turned out to be a seized sliding caliper on the front. The brake pad was only pressing properly on one side of the disc, causing judder. The cause was a split rubber gaiter on the caliper slide, causing the slide to seize up. If you've got a lot of wear on one brake pad, and not much wear on the other brake pad, then it might be an indicator or this problem.

Paul

Xaccers · Post by **Xaccers** » 18 Sep 2010, 22:28

Dave, did you check the LHM level with the car set on high or normal?
If it was on normal then you've over filled it, hence the loss of the excess LHM, nothing to worry about, just messy.

If memory serves, the way the brakes are set up, if you had a LHM leak (other than from the brake system which would be the same with crappy brake systems that love soaking up water on other cars) it wouldn't drain from the brake system. If you lost complete hydraulic pressure, you'd still have the hand brake on the front wheels to safely slow you down.

HDI Dave · Post by **HDI Dave** » 18 Sep 2010, 23:21

Paul/weaver,

Yeah,fair point mate, I usually do visual checks of the pads/callipers etc,they seem fine,that's why it's so baffling!

Xac, yes, I check the lhm on high,engine running,as advised in the manual,sorry for the confusion,I was referring to the normal method of lhm checking.
re the brake system, Lol, I know you're going to stick up for the citroen method, fair do's,it's a citroen forum

, but a 'normal',hydraulic brake fluid system does not soak up that much water in its fluid system to render it useless,plus you'd still have fluid; I was just wondering how citroen brake systems work, if say you lost all the lhm?
Brakes,suspension,etc all dies?
And does an lhm system have a backup,like opposite linked braking systems ala 'normal' brake fluid filled cars,ie, if one brake circuit fails there's a backup,nsf linked to osr and vice versa etc

And the handbrake..why have it on the front! The front disks get hotter don't they..park the car up,handbrake on, disk cools down,shrink, car rolls off

Much more controllable on the back.
Plus, more fun in the snow

I'm not totally anti citroen, they're just weird! Why???

Mind you,spose they can be quite endearing.. like addo's quip, they're like camels waking up in the morning,arse up,then front,tick etc

Xaccers · Post by **Xaccers** » 18 Sep 2010, 23:54

Why on the front? Because the cars sink.
Doesn't make a difference to the frong wheels, but the back ones being on trailing arms rotate as the car sinks, if they were locked with brakes then they'd not be able to move and would put the suspension under stress.
As for the discs shrinking, thats why the front pistons have very strong springs in them to take up the slack.

For losing all the LHM, you'd have to have multiple failures in the brake lines and the rest of the system.

Dommo · Post by **Dommo** » 19 Sep 2010, 08:11

The handbrake being on the front wheels is because if the hydraulic system does fail, the front wheels are likely to stop you more safely than the rear wheels. Also, the rear trailing arm layout, if you park pointing down a hill in a 306 or ZX for example (or many trailing arm cars) the back end will sag, if you park pointing up a hill the back end up go up on stilts. If a hydraulic Citroen did this, the height correctors would try and correct for it, so when you let the handbrake off, if you're at traffic lights for example, the rear of the car will either shoot off into the sky (downhill slope), or sink right down (uphill slope).

dave m · Post by **dave m** » 19 Sep 2010, 17:09

I believe the reason for the parking brake on the front discs is that it is an emergency brake. Try actually stopping from speed with almost any other car on the "parking brake" and see!

Post by **CitroJim** » 19 Sep 2010, 19:05

dave m wrote:I believe the reason for the parking brake on the front discs is that it is an emergency brake.

Yes, that's true as they're not genuine dual-circuit brakes. However, it is more for the reasons Dommo and others state. If the handbrake was applied to the rear wheels, due tho the changing geometry with height as a result of the trailing arm layout, the self-levelling would fail with the brake applied and then when released, cause a very rapid and alarming change in height.

Us drivers of automatics know all about that

dave m · Post by **dave m** » 19 Sep 2010, 19:38

Think about it guys,if the brake,fixed to a trailing arm is applied while static,that's it! Any loading of sufficient force to alter the wheelbase is simply dealt with as weight as the front wheels are free to rotate. The concept of the larger front disc being an emergency brake goes back many models in time on hydraulic Citroens. It is a workable secondary brake in most cases.On the Xantia the bean counters may have prevailed regarding the inclusion of a preload spring to eliminate cooling discs causing loss of grip.

dave m · Post by **dave m** » 19 Sep 2010, 20:39

Just a p/s having a spring in the system would not improve the 'e' brake but would much improve the parking brake.....cheers

HDI Dave · Post by **HDI Dave** » 19 Sep 2010, 21:59

Ahh yes,good point..trailing arms need a different setup,
especially if it's a sinker,which I suppose would indeed alter the 'normal' setup / geometry

So all trailing arm cars have the handbrake on the front?
And yes the front brakes would stop the car quicker in an emergency, 70 / 30 bias etc and all that,so I can see why they do that as well.

dave m wrote:On the Xantia the bean counters may have prevailed regarding the inclusion of a preload spring to eliminate cooling discs causing loss of grip.

Well not on my car they aint

and plenty others I've heard. My car rolled away at least twice with the previous owner, and has rolled away with us! Now it's always parked in gear, (which I always have done anyway),with the wheels turned..I just don't trust it

Sorry OP for steering your post off topic a bit

If it weren't p!$$ing it down today I 'd have had a go at the brakes and reported any change.

Cheers, Dave.

Xaccers · Post by **Xaccers** » 19 Sep 2010, 22:15

Sounds like you either need to replace your handbrake cables or at least adjust them properly.
Which reminds me I must adjust Cassy's.
Before I changed her cables she was impossible to move on just one click of the lever.

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