Sticking front brakes

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billywhizzz40
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Sticking front brakes

Post by billywhizzz40 »

Help.... I have just bought myself a 'bargain' Xantia 2.1tdSX. The front brakes were supposed to have been fixed prior to my purchase but they still grab and stick on, It seems only to do this when they get hot and they do release after a while. When you stop at traffic lights and then move away you can fel that they are still applied. Is it likely to be hoses or dodgy calipers, offside worse than nearside.
Ps it has done 162k! 1998 R(facelift)
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Post by Peter.N. »

They probably just want a good clean. Take the pads out and make sure that the caliper slides freely, lift the edge of the neoprene seals on the pistons and squirt some LHM fluid in, that should unstick them.
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Mandrake
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Post by Mandrake »

Also try winding in the piston one or two turns while you have the pads out, and then let it readjust itself - if you're unlucky the ratchet for the handbrake adjustment can click over such that it *just* binds the brake.

I had this happen to me when I put new pads in, after they auto-adjusted themselves the left caliper was binding, which made it rather difficult to swivel up to fix the problem... :oops:

After winding the piston in a couple of turns and letting it self adjust again (apply full brake force when the caliper was reassembled) it was fine...

Regards,
Simon
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Post by bxbodger »

Both sides or one side??

Is the handbrake adjusted properly? Try loosening the adjustment on each caliper to see if it makes a difference.

It could be internal hose failure (easy to check-take the hose off and blow through it both ways: there should be no difference), but it would be unlikely that both hoses would fail at the same time.

The most likely cause is pad/disc wear.Check the discs for wear-if there's a pronounced wear ridge, then that prevents the pads from releasing properly.New pads/discs will stop it happening.
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Post by Mandrake »

bxbodger wrote:It could be internal hose failure (easy to check-take the hose off and blow through it both ways: there should be no difference), but it would be unlikely that both hoses would fail at the same time.
Not sure that I understand what blowing through the hose both ways would establish :?: If the hose was internally collapsing it happens when the brakes are removed, which causes suction on the pipe, and the inside of the hose to collapse, blocking the return flow.

Regards,
Simon
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Post by bxbodger »

What happens is that when damaged the hose acts as a one way valve, keeping the pressure on even though you've taken your foot off, preventing the brake from releasing properly. It cost me a replacement caliper on my old 205 to find this out :oops:

I put the new caliper on, it still kept sticking, so I replaced the hose-hey presto, working brake, and blowing through the old hose it was easy one way, but not the other- it was like blowing through one of those cheapo brake bleeders you used to be able to get: only possible one way.
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Post by billywhizzz40 »

Thanks for the advice. One final question, how do you wind in the handbrake mechanism, do you need special tool?
handbrake is adjusted so it come up about three clicks before on.
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Post by Mandrake »

billywhizzz40 wrote:Thanks for the advice. One final question, how do you wind in the handbrake mechanism, do you need special tool?
handbrake is adjusted so it come up about three clicks before on.
The piston has some square slots in it, so a T-bar of the right size is the way to go. At a pinch you could use a screwdriver or a pair of polyplyers if you're only turning it a couple of turns.

By the way that just affects the pad wear auto-adjuster, (which can only compensate in one direction - if it manages to move too far out it can't go back in by itself again) the actual handbrake adjustment is seperate to this.

It's the two nuts on the handbrake cable, and it should be adjusted so that when you pull on the outer cable sheath by hand to take up the slack in the centre wire of the cable (with the handbrake off) there is a 1.5mm gap between the nut and the face it normally rests against.

3 clicks might not be enough slack, and could cause the pads to drag during cornering, so check the gap adjustment on both sides...

Regards,
Simon
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Post by jeremy »

3 clicks may be the correct adjustment and may not be - it depends on the age of the car!

Originally the Xantia had the same arrangement as the BX which is an extremly fine toothed ratchet. The brake itself is superbly eficient and indeed I have a roadtest of a BX where the thing achieved 0.52G which is actually up to minimum MOT standards for a footbrake!

So you vave a superbyl efficient disc handbrake and peoples tendancy is to apply it just enough to hold the car. This is no problem when the whole system is cold - but - you pull up with hot brakes, set the brake gently which holds the car and walk away. The hot brakes now start cooling and being discs get narrower - and yes the car rolls away - and did actually kill a number of people.

Citroen modified the brake lever by fitting a coarse ratchet and removing a considerable (6?) teeth from the bottom end of the ratchet - forcing the driver to pull it on much harder.

3 clicks may be enough - I'd judge it on the feel and the angle of the lever. If its sticking straight up its too slack. Try applying the brakes with the engine running and putting the handbrake on and off a few times! - it may tighten up!
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Post by Mandrake »

jeremy wrote:3 clicks may be the correct adjustment and may not be - it depends on the age of the car!

Originally the Xantia had the same arrangement as the BX which is an extremly fine toothed ratchet. The brake itself is superbly eficient and indeed I have a roadtest of a BX where the thing achieved 0.52G which is actually up to minimum MOT standards for a footbrake!
The handbrake on mine also (just) meets the minimum requirement for the footbrake :)

And on the front footbrake I get 280% of the required minimum :)
So you vave a superbyl efficient disc handbrake and peoples tendancy is to apply it just enough to hold the car. This is no problem when the whole system is cold - but - you pull up with hot brakes, set the brake gently which holds the car and walk away. The hot brakes now start cooling and being discs get narrower - and yes the car rolls away - and did actually kill a number of people.

Citroen modified the brake lever by fitting a coarse ratchet and removing a considerable (6?) teeth from the bottom end of the ratchet - forcing the driver to pull it on much harder.
So I've heard, but I've never come across one thats been modified ? My 1997 certainly isn't, it starts clicking right near the bottom, and has a fine ratchet.

Maybe they didnt bother to modify automatic's because of the park mode in the gearbox ? (I knew there had to be SOMETHING good about automatics :lol: )

"normal" firm application of the handbrake on mine is about 10 clicks, which is about 30 degrees, and thats with the aforementioned 1.5mm adjustment correct.

Regards,
Simon
Simon

1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
2016 Nissan Leaf Tekna 30kWh in White

2011 Peugeot Ion Full Electric in Silver
1977 G Special 1129cc LHD
1978 CX 2400
1997 Xantia S1 2.0i Auto VSX
1998 Xantia S2 3.0 V6 Auto Exclusive
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