Partially fixed Xantia brakes, help!

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cc101
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Partially fixed Xantia brakes, help!

Post by cc101 »

Hi all, in a previous post a mentioned that my brake pedal was vibrating when pressed, followed this forums advice by bleeding the brakes which made a huge difference and stopped the vibrating
pedal! But, when I brake I get like a surging sensation, lots of power then it gives then grabs again as if the brake discs are warped, also if I brake in reverse I hear and feel a knock as if the pads or caliper are moving, the brakes only do this knocking business when reversing!
(1994 TD LX, no ABS, sinker)
Thanks in advance all,

Chris.
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Re: Partially fixed Xantia brakes, help!

Post by Old-Guy »

Brakes surging slightly seems to be a normal effect of the brakes taking their pressure supply from the suspension. If the surging is bad, I think you'll find it's down to sticky height correctors - i.e. not responding smoothly to weight transfer under braking. Been there myself, though the surging wasn't alarming - just got complaints about my driving! :oops:
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Re: Partially fixed Xantia brakes, help!

Post by Xaccers »

I wonder if it could be due to corrosion build up between the rear arms and the callipers?
It pushes the callipers out at an angle and can get so bad the calliper bolts snap or the calliper touches the disc and the rear brakes can't work.

Whip the rear wheels off, look down from above, if the callipers and discs look like this ]|[ you're OK, if they're like this ]/[ you've got to take the callipers off and chip away the build up, then grease up the surface before re-fitting.
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Re: Partially fixed Xantia brakes, help!

Post by cc101 »

Thanks for the quick reply guys, reference the surging I had a mk2 xantia a few years back and the brakes didn't do this, sometimes it is quite scary as the brakes seem to let go then apply! Funny about people complaining about my driving!

The knocking is definitely coming from the front end when reversing and braking!

Thanks again!
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Re: Partially fixed Xantia brakes, help!

Post by cc101 »

Hi all, does anyone have any further ideas as this surging feels dangerous, as your approaching say a juntion, the brakes grab then let go then grab again, very scary!
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Re: Partially fixed Xantia brakes, help!

Post by citronut »

try bleeding the brake all round as it could be air in the system, which may even be upsetting the ABS if fitted
Regards, malcolm.

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Re: Partially fixed Xantia brakes, help!

Post by cc101 »

Will do thanks Malcolm, I did bleed the brakes a week ago but have since changed all corner spheres so maybe air has got in. No abs on my xant. Thanks for the quick reply.
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Re: Partially fixed Xantia brakes, help!

Post by myglaren »

What is the condition of the accumulator - if it is flat the pulsing could be the hydraulic pump or regulator.
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Re: Partially fixed Xantia brakes, help!

Post by Old-Guy »

cc101 wrote:I did bleed the brakes a week ago but have since changed all corner spheres so maybe air has got in.
Highly likely as the rear brakes take their pressure from the rear suspension - and, unlike the suspension circuit, are a dead end. Almost impossible to change spheres without letting air into the circuit. I bet that when you re-bleed the brakes you get bubbles out of the rear lines - don't forget that you need to bleed something like 250ml from each rear calliper because the lines are so long; anti-sink sphere all the way forward to the Doseur valve and then back to the callipers.

I agree entirely with Myglaren that a (near-)flat accumulator may well be the cause of your problem.

Try the 'sit-on' tests for both front Accumulator and rear 'Anti-sink' spheres, the latter is really an accumulator for the rear suspension and brakes.
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Re: Partially fixed Xantia brakes, help!

Post by citronut »

i have never know replacing spheres to cause air in the brake circuit,

but a flat accumulator sphere can dump its gas into the system which in turn can get into the brake circuit
Regards, malcolm.

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Re: Partially fixed Xantia brakes, help!

Post by CitroJim »

Another cause can be air getting into the LHM through a porous pipe. Often the supply pipe to the pump. It's under suction so won't leak but it can suck air.

Have a look in the LHM reservoir with the engine just above idle. Is the LHM all foamy? If so you have an air leak and all this air will eventually get into the brakes...
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Re: Partially fixed Xantia brakes, help!

Post by cc101 »

Thanks all, will try your suggestions and let you know how I get on.

Chris.
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Re: Partially fixed Xantia brakes, help!

Post by citroenxm »

Old-Guy wrote:
Try the 'sit-on' tests for both front Accumulator and rear 'Anti-sink' spheres, the latter is really an accumulator for the rear suspension and brakes.
Tis a sinker.... NO anti sink valves, and no rear "anti sink Sphere" either... :wink:
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Re: Partially fixed Xantia brakes, help!

Post by Gibbo2286 »

Does this have ABS If so are the reluctor rings secure? One of my Xantias had a split reluctor ring where the rust had gone right through and it was loose and turned on braking causing the pedal to kick back/bounce.
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Re: Partially fixed Xantia brakes, help!

Post by citroenxm »

As the first post says.. 94 Lx sinker with no Abs...
Sharing a pug 207 1.6 hdi Sw 16v.
M reg Xm 2.1 td auto exclusive S2 269k and rising
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