New brakes overheating - Citroen ZX - DHJ
9 months / 4000 miles ago I had a total brake failure on my 1997 Citroen ZX 1.4i, apparently due to fluid fade. The offside front got so hot that the disc turned blue and the insulation melted on the pad wear sensor wire. My local authorised Citroen independent diagnosed a faulty OSF calliper causing binding & consequent overheating, and fitted new front callipers, discs and pads both sides. (Also rear cylinders and shoes as these were poor.)

The other day I had a loss of braking efficiency and a smell of friction material after coming down a big hill. I'd used a low gear to control speed but still had to brake fairly firmly behind a slow caravan. After parking shortly afterwards, I found that the offside front was very hot, considerably hotter than the nearside. I inspected the brakes next day and found that the offside disc had a continuous band of grey discolouration, over about a quarter of the width of the disc surface. Turning the disc by hand, it was a little tight most of the way round but freer over say 60-90 degrees. The nearside disc had no discolouration and movement was freer and more even. A friend thought the discs looked slightly glazed. Plenty left on the pads, both sides. The plastic offside pad wear sensor connector block was partly melted away on the side facing the disc. I don't know whether this got replaced when the callipers were done.

The callipers are marked "REMAN", presumably remanufactured. I naively assumed I was getting new callipers, but AFAIR I wasn't explicitly asked or told. They have a Bendix logo and consecutive serial numbers.

I hadn't checked the wheel temperatures before this, but I now find that after every journey the offside is quite a lot hotter than the nearside.

My main worry is that I once again have an overheating offside front, which previously resulted in a scary brake failure. What might cause the same side to overheat despite having new callipers, discs & pads both sides? There's no temperature difference between the back wheels, which I imagine there might be if the cause was weakness in one circuit? Perhaps it's just co-incidence and I got a dodgy reconditioned offside calliper.

The previous work is under guarantee. I'd appreciate advice on what I should demand (nicely, of course!) from the garage.

Thanks,
Dave.
New brakes overheating - Citroen ZX - Hamsafar
I'm not familiar with the car, but is the master cylinder on the driver's side, some cars such as 1980s BMWs have the master cylinder on passenger side and a linkage which goes across, this can become stiff at the pivots and mean the brakes are dragging when you aren't pressing the pedal.

New brakes overheating - Citroen ZX - madf
" I inspected the brakes next day and found that the offside disc had a continuous band of grey discolouration, over about a quarter of the width of the disc surface. Turning the disc by hand, it was a little tight most of the way round but freer over say 60-90 degrees."

Sounds to me that the disk has not seated properly on the hub which means the pads will drag on part of the disk. Or the disk has not been correctly machined..or both

Or the wheel bearinsg are failing due to the prior overheating.. and dragging slightly (but unlikely although the race carriers could be damaged by excess heat if prolonged..)

Take it back to the garage to sort it out is my advice..
madf
New brakes overheating - Citroen ZX - Civic8
Sounds to me that the disk has not seated properly on the hub which means the pads will drag on part of the disk. Or the disk has not been correctly machined..or both

This occurs on a lot of cars, but doubt this is the problem,more likely a caliper problem
--
Steve
New brakes overheating - Citroen ZX - bell boy
or sticky pads,i would be inclined to take it back and let the garage have a look before you warp a disc etc
New brakes overheating - Citroen ZX - Pete M
I wonder whether the new calipers were shimmed to be central around the disc when they were replaced. I haven't owned a citroen, so this may not be necessary, but I know it is on some other cars. This shouldn't cause problems, but it is worth a look. Another thought is that if the calipers etc overheated, were the flexible hoses to them replaced? Overheating could cause the inner liner of the flexible hose to collapse. This would tend to trap fluid in the caliper, maintaining a small but constant pressure on the pad and giving the results you describe.

New brakes overheating - Citroen ZX - RichardW
No need to shim the calipers - it's a single pot floating design, and the master cylinder is on the driver's side. It's clearly not right, so I'd take it back. Either the new caliper is sticking again (ZX front brakes are not always the best for staying free, but this mostly affected early cars -the later ones should be OK), or as noted the hose is restricting the return of fluid. As it's under guarantee, get it taken back pronto. I'd be demanding new discs and pads again - it might never be right if it's overheated again.
--
RichardW

Is it illogical? It must be Citroen....
New brakes overheating - Citroen ZX - Collos25
I had once a caliper heating up we changed the caliper to no avail after a lot of head scratching I changed the flexible hose and this cured it.I cut the offending hose open and found a piece of the rubber was braking away causing the effect of a oneway valve.
New brakes overheating - Citroen ZX - DHJ
Thanks everyone for the replies. The offside front flexible hose (the side that overheated) was replaced when the callipers were done. The master cylinder is indeed on the driver's side.
New brakes overheating - Citroen ZX - robcars
Take it back to the garage. Lots of things it could be, a faulty caliper included amongs others.

But. It's your brakes and its your life and others at risk; so dont take chances just return to the garage, explain the situation, and infrom them that you would like them to re look at it before you have an accident and the associated aggro that may go with it.

Any reputable garage will be pleased at the chance to look at it and cure it .

remember, if you are happy with whats been done tell everyone. if you got a problem, tell us. Most good garages stick to that motto.
New brakes overheating - Citroen ZX - DHJ
Thanks for the advice. I've already booked the car in for Monday. It's good to have some informed opinions about possible causes of the recurring problem on the offside front, and advice about what I should expect the garage to do, so that I'm reasonably well informed when I go in. I think they're a decent garage - they say they were awarded 1st position for after-sales service in UK for Citroen - but I haven't been using them long.

I was surprised to see "REMAN" stamped on the "new" calipers, is it normal practice to fit remanufactured calipers without consulting the customer? Not that I could have afforded new ones, I dare say! I found a post on this forum from someone who'd had recon calipers last less than a year: www.honestjohn.co.uk/forum/post/index.htm?v=e&t=86...9 - I'd be interested in people's experiences.

Thanks,

Dave
New brakes overheating - Citroen ZX - robcars
i think it would be standard practice.

Nothing wrong with reconditioned stuff like that as longas its quality reconditioning (not cheap repairing and spray paint over). But admit its difficult for a non trader to know a good reconditioned unit from another.

Same goes for alternators/starters.
New brakes overheating - Citroen ZX - autumnboy
Dave,

if you do not have any joy in curing your fault, try the Website dedicated to Citroen's :-



www.frenchcarforum.co.uk/forum/index.php
New brakes overheating - Citroen ZX - DHJ
Update: I took it back to the garage today, they say they tried hard to find something wrong but couldn't. They cleaned & lubricated & made sure the calipers were operating freely. Also checked on rolling road. After the 1-mile journey home with only gentle braking, the offside front wheel nuts were uncomfortable to touch for more than 2-3 seconds, whereas the nearside were only starting to become uncomfortable after 8-10 seconds. I think I'll take it for a good old spin, then straight round to the garage and invite them to feel my nuts. Sorry.

Thanks for the French Car Forum link, several mentions there of sticking front calipers on ZXs, though from what I've read elsewhere this mostly affected early ZXs with a Girling caliper, mine are Bendix. Interestingly, the majority of problems reported seem to be on the offside.
New brakes overheating - Citroen ZX - Number_Cruncher
To fiond out what is going on, I suggest either you or your garage try the following.

Drive the car round a bit, until the brake sticks on.

Jack up the problematic front wheel.

Try to turn the wheel, and feel how much resistance there is.

Open the bleed screw, and see if fluid jets out.

Try to turn the wheel, and see if it has freed off.

Bleed some fluid through before using the car again - to make sure that you haven't introduced any air.

This procedure will isolate whether you have a purely mechanical problem in the caliper - or if the caliper is doing as it is told, and you have a hydraulic problem upstream - a faulty inner flexi - for example.

Number_Cruncher
New brakes overheating - Citroen ZX - DHJ
The offside front is still getting a fair bit hotter than the nearside every journey; the garage's clean & lube doesn't appear to have changed anything. Good news is that it doesn't get a lot hotter on a long trip than a short one. I took another look yesterday:

Offside: band of discolouration previously noticed on the disc had gone. Disc a bit stiff to turn by hand, freer over about 1/4 of a turn, as before. Could hear pad rubbing against disc as I turned it. Could see daylight between the inner pad and the disc - therefore not a hydraulic problem, I take it. Outer pad was in contact with the disc surface. These are Bendix single-piston calipers, presumably the inner pad is the one attached to the piston. So I'm guessing the piston is retracting OK, but the caliper isn't sliding as freely as it should - does that sound right, or have I misunderstood how these calipers operate?

Nearside: disc freer to turn than than offside. Could see a tiny bit of daylight between each pad and disc. Noticed that on turning disc, gap between disc and pad varied slightly, by a hair's breadth or two. Haynes gives max run-out as 0.2mm, I'd guess it was in that sort of range.

I'm not sure what to do now, the garage have already pronounced that the calipers are operating correctly.
New brakes overheating - Citroen ZX - Simon
Have the garage had it on some brake testing rollers, like the ones used for MOT's? That will show you whether the brakes are binding or not.
New brakes overheating - Citroen ZX - Civic8
>>but the caliper isn't sliding as freely as it should - does that sound right,

It does, in that if the sliders are only cleaned and not lubricated as I have seen before,they wont work properly and drag/stick.Once lubricated they should be fine for several years assuming dust covers are not split in any way
--
Steve
New brakes overheating - Citroen ZX - 659FBE
I tend to agree that the sliders are the most likely cause of problems here. The Bendix sliders have rubber bellows type boots (complete with little tin heat shields) and it is essential that the boots are intact, that there is the correct grease underneath the boots and that everything is free. At each service, I remove the pads and exercise the sliders throughout their travel - this also helps to spread the grease.

I did have one other case of sticking Bendix brakes not caused by the sliders. The pad backplates on these calipers fit like a jigsaw with dovetailed ends into the brake carrier, retained at one end by a wedge to facilitate pad removal. I found that a set of well known branded pattern pads were not a sufficiently free fit in the carrier and were binding at the dovetail ends, giving sticking brakes. The remedy was a light dressing of the dovetail ends of the pad backplates with a fine file (I suspect they were burred when the backplates were stamped out) and the application of a little copper loaded anti-seize compound where the backplate ends slot into the carrier.

659.

New brakes overheating - Citroen ZX - Mike-H
There has been lots of sound advice given here, but here,s my six penneth. What retracts a brake piston a few microns after the brake has been let off, and allows the disc to spin freely, is the piston seal. When hydraulic pressure is applied, the seal 'drags' on the smooth caliper bore, and distorts slightly. It's a bit like stretching a rubber band sideways. Once the hydraulic pressure is released, the rubber retutrns to its natural shape pulling the piston back a tad as it does so. I have come across this fault a few times, and it can only be rectified by removing the pistons and seals, cleaning all the gunge out which can make the piston stick, (and there will be plenty) and rebuilding, preferably with new seals. Or a new caliper1The piston only needs to move back slightly to release the brake. The odd thing here is that the piston will feel perfectly free when pushing it back by hand, but stiff enough to prevent the seal doing the job. This is easier said than done with some calipers, as the dust seals can be impossible to remove to get the pistons out. I reckon everything else has been done, so it stands agood chance of curing it, I hope so. Mike
New brakes overheating - Citroen ZX - robcars
What does the garage say to 1 side getting hotter than the other?

Are they considering replacing caliper under warranty? or have they better ideas yet?
New brakes overheating - Citroen ZX - DHJ
Have the garage had it on some brake testing rollers, like the ones used for MOT's? That will show you whether the brakes are binding or not.

Yes, and they say they didn't find anything wrong. But is it it possible, if a pad is rubbing on one side of a disc as seems to be the case here, for there to be enough friction to cause noticeable heating without this showing up on the rolling road?

I did have one other case of sticking Bendix brakes not caused by the sliders. The pad backplates on these calipers fit like a jigsaw with dovetailed ends into the brake carrier, retained at one end by a wedge to facilitate pad removal. I found that a set of well known branded pattern pads were not a sufficiently free fit in the carrier and were binding at the dovetail ends, giving sticking brakes

Could this problem affect either pad on a single-piston caliper, or only the one on the inner (piston) side?

What retracts a brake piston a few microns after the brake has been let off, and allows the disc to spin freely, is the piston seal...

I was thinking that since it's just the pad on the outer side that's rubbing, which I believe is the pad that isn't attached to the piston, then I can rule out causes related to piston movement & hydraulics. If I've got this wrong I'll be happy to be put right!

The car's going back to the garage tomorrow for another look.
New brakes overheating - Citroen ZX - Civic8
I think I would look at other poss reasons for this,As no fault found on caliper,would look at possible brake pipe flexi fault,ie nothing to say pipe has not collapsed internally holding the pads on/apart from that I can only think faulty wheel bearing transfering heat through hub and nothing wrong with calliper
--
Steve
New brakes overheating - Citroen ZX - Mike-H
I was thinking that since it's just the pad on the outer side that's rubbing, which I believe is the pad that isn't attached to the piston, then I can rule out causes related to piston movement & hydraulics. If I've got this wrong I'll be happy to be put right!

It's only the piston retracting that gives any free play at all, at either side. The free play should then be equalised by the sliding pins, so both sides have enough and the same. If the pins are stiff, then the free play will be mostly on the piston side, quite rightly stated, but if there is insufficient retraction of the piston for both sides to have enough free play, the piston side will be the first to get it, is because of frictional losses in the sliders, so the floating side will rub. It's difficult to explain here, I hope it makes sense! Mike


New brakes overheating - Citroen ZX - 659FBE
It was indeed the outboard pad which was sticking due to a lack of freedom at the pad backplate dovetailed ends. It's easy to see how Newton's Third Law applies to the sliders in terms of actuating the outboard pad, but if you study the whole caliper and carrier assembly carefully, you can see that the pads have to move in the carrier when the brakes are applied, and also have to move back again.

I would put my money on a lack of freedom at the pad backplate ends where they dovetail into the carrier.

659.
New brakes overheating - Citroen ZX - Civic8
>>I would put my money on a lack of freedom at the pad backplate ends where they dovetail into the carrier.

Highly poss 659,but that would wear pad at hub side assuming rest of pad is free
--
Steve
New brakes overheating - Citroen ZX - Civic8
>>but if there is insufficient retraction of the piston for both sides to have enough free play, the piston side will be the first to get it,

No if piston is retracting as it should then the drag factor will be on float side ie sliders if they dont work as should/causing the other pad to stick in place.

as long as the piston is working correctly,pad on that piston will retract.the calliper on piston side is fixed to rear of hub/float side is only connected via the sliders so if they fail then pad drag will occur...If they are found to be working properly and both pads are free of disc(excluding disc runout ) this often occurs without any problems,

Need to look at other problems as mentioned
--
Steve
New brakes overheating - Citroen ZX - 659FBE
I can't quite understand your comments.

A simple but revealing experiment: Assuming pads are partly worn, retract piston and fully assemble caliper with both pads as far away from the disk as is possible. Arrange for the pad to disk gaps to be about equal.

Now get someone to slowly press the brake pedal whilst you watch all the free movement being taken up. The movement of the pad backplate ends relative to the carrier will be very obvious.

659.
New brakes overheating - Citroen ZX - DHJ
Quick update: the car's currently at the garage. When I took it in, the head man said they get a lot of problems with ZX front brakes, with the single-piston caliper design not working so well as the car gets older. He said the only thing that causes the outer pad to rub is the caliper not sliding correctly, and that since the operation of the caliper itself has already been checked, the next thing to look at is where the caliper is mounted to the hub. He said these are sometimes not aligned correctly and that this can cause the caliper not to slide freely. Make any sense? I await their call.
New brakes overheating - Citroen ZX - DHJ
The garage have phoned to say they still can't find anything wrong. Their next suggestion is to try a new master cylinder, in case a faulty valve is causing the problem. That doesn't seem to fit with my observation that only the outer pad seemed to be rubbing. They say I was mistaken if I thought I could see daylight between the inner pad and the disc, as the gap is never big enough for this to be the case. Comments on that are welcome!
New brakes overheating - Citroen ZX - 659FBE
Fitting a new master cylinder to overcome stiction in one service brake (only) is ridiculous. The daylight obsevation is quite valid - I've seen it too with disks and pads in good running condition.

I reiterate my earlier comments - try my experiment and you will see why free movement between the ends of the pad backplates and the carrier is so vital for the proper functioning of this design of caliper.

659.
New brakes overheating - Citroen ZX - DP
Fitting a new master cylinder to overcome stiction in one service
brake (only) is ridiculous. The daylight obsevation is quite valid -
I've seen it too with disks and pads in good running
condition.


I agree with 659.

Cheers
DP
New brakes overheating - Citroen ZX - bell boy
ive just read the 11.17 post and yes the caliper holding brackets do bend with zealus use of screwdrivers to push pistons back and this will indeed cause the sticking pad,if i was the garage i would be changing this £10 part before a £150+ master watsname........
New brakes overheating - Citroen ZX - Mike-H
I agrre too with 659. It's rubbish. Ask then to name the valve in the master cylinder which could cause one pad or piston to stick. This will allow you to judge whether or not there is any theory or reason behind this suggestion, other than their bonus and your cash. I have come across the actuator rod which connects the pedal to the master cylinder to have no free play, so that the master cylinder piston will not fully retract , and not uncovering the ports, so as the fluid heats up and expands naturally with breaking, the brakes apply as the fluid cannot get back to the cylinder. With a diagonal split I suppose one front and the other back may come on first., but doubt this is the problem here. ask them!
New brakes overheating - Citroen ZX - DHJ
Sorry to post again, another call from the garage. They took the car out for a test drive for 10 mins then checked the temperature of both front wheels with a digital thermometer and they say they were the same. Which doesn't seem to fit with my own observations based on feeling the wheel nuts after numerous journeys. The mechanic I spoke to had owned a few ZXs and said they're known for the brakes getting hot and occasional fade. (I've read elsewhere of people fitting Berlingo ventilated discs & calipers to ZXs to improve braking.)

Basically they're saying they haven't been able to reproduce the fault or find any mechanical problem. They're not ruling out that there is a problem that intermittently causes binding and consequent overheating during use. They believe they've ruled out the caliper as the cause. I want to re-check my observation of clearance between inner pad & disc before spending money on hydraulics.
Fitting a new master cylinder to overcome stiction in one service brake (only) is ridiculous.


Their explanation was that the master cylinder has a valve that can produce a fault affecting only one braking circuit. I don't know enough to evaluate this.
The daylight obsevation is quite valid - I've seen it too with disks and pads in good running condition


Thanks for the information and for your vote of confidence in my powers of observation! I was beginning to doubt what I thought I'd seen.
I reiterate my earlier comments - try my experiment and you will see why free movement
between the ends of the pad backplates and the carrier is so vital for the proper functioning
of this design of caliper.


I have resisted fiddling so far because I don't want someone who doesn't know what they're doing (i.e. me) fiddling with my brakes, and because the work is supposed to be under guarantee. But I'm inclined to believe you. I don't think the garage are going to do any more, so I suppose I've nothing to lose by trying filing the pad backplates. I've never fiddled with brakes but I have the Haynes manual, are there any pitfalls I should know about?

Thanks everyone for your helpful and informative comments, much appreciated.
New brakes overheating - Citroen ZX - 659FBE
Thanks for your kind words.

If you file the pad backplates, bear in mind that you will be removing an absolutely minute amount of metal - little more than the thickness of the paint. It's really the burr on one side which is caused by the stamping process which needs to come off. Don't under any circumstances remove a significant amount of metal and make sure you use high temeperature copper loaded anti-seize compound (never ordinary grease) at the very ends of the pad backplates. Keep this compound well away from the friction surfaces.

My feelings are that the garage have themselves temporarily "cured" this problem simply by removing and refitting the pads, but unless you take action, the fault will come back.

One final point. Before you start, make sure you know exactly how the pads, wedge and anti-rattle springs are fitted. Make a diagram or use a camera. The pads are handed, although they look very similar and it's easy to get it wrong.

659.
New brakes overheating - Citroen ZX - Mike-H
Yes, to avoid the trauma that 'deep diver' has had over the weekend (read the threads) if you need to push the caliper piston back to get the pads out, undo the bleed nipple to let the the fluid escape, don't force it back though the hydraulics into the master cylinder. Good luck.
New brakes overheating - Citroen ZX - autumnboy

>I don't think the garage
are going to do any more, so I suppose I've nothing
to lose by trying filing the pad backplates. I've never fiddled
with brakes but I have the Haynes manual, are there any
pitfalls I should know about?

.


If you try and file the Pad backplates, you'll remove as most pads have is an Anti-squeal material bonded to the plates, this contacts the piston and caliper.

If you follow the manual you should have no problem.



New brakes overheating - Citroen ZX - Civic8
>>If you try and file the Pad backplates, you'll remove as most pads have is an Anti-squeal material bonded to the plates, this contacts the piston and caliper.

Shouldnt need to unless pads are wrong thickness/not correct pads for car!

--
Steve
New brakes overheating - Citroen ZX - autumnboy
>>If you try and file the Pad backplates, you'll remove as
most pads have is an Anti-squeal material bonded to the plates,
this contacts the piston and caliper.



Shouldnt need to unless pads are wrong thickness/not correct pads for
car!
--
Steve


Steve,

Read my replies again, they are in reply to the above threads.

I am not suggesting the pads be filed, as you say they should not be touched.


New brakes overheating - Citroen ZX - Civic8
autumnboy,Fair comment,But would think any garage worth there name should have sorted this problem out much quicker than they have.

also tend to agree with comment about the wheel bearing CV joint,I also suggested wheel bearing some posts ago
--
Steve
New brakes overheating - Citroen ZX - Civic8
>>next thing to look at is where the caliper is mounted to the hub. He said these are sometimes not aligned correctly and that this can cause the caliper not to slide freely. Make any sense?

No,its secured ,no way of adjusting its mounting..its a precise fit with bolts,ie once fitted its secure/unless they did not tighten the bolts correctly,I dont think oldmans comments were totally correct but severe force on calliper could missalign it but it would have to be severe force
--
Steve
New brakes overheating - Citroen ZX - bell boy
seen it done but to be fair it was a 106 not a zx......(with 2 different people and two different cars i might add) a tool was placed to push the piston back but because the piston was semi seized the holding bracket twisted,everything bolts back but the non piston loaded pad sits at a slight angle and jams within days/weeks

its only an observation mind........
New brakes overheating - Citroen ZX - autumnboy
Quick update: the car's currently at the garage. When I took
it in, the head man said they get a lot of
problems with ZX front brakes, with the single-piston caliper design not
working so well as the car gets older. He said the
only thing that causes the outer pad to rub is the
caliper not sliding correctly, and that since the operation of the
caliper itself has already been checked, the next thing to look
at is where the caliper is mounted to the hub. He
said these are sometimes not aligned correctly and that this can
cause the caliper not to slide freely. Make any sense? I
await their call.


Mine has done 172k with no problems in ten years although mine are vented disc's.

If there was a problem with the Master Cyl. you would have more than one brake getting hot, also they a dual system.

If you say its the wheel nuts that feel hotter than the other side, then this suggests the hub bearing or CV joint is the cause rather than the brakes.


 

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