Faulty front brake hoses ?

Mandrake · Unread post by **Mandrake** » 13 Jun 2006, 22:21

Hi All,

Ever since I've had my Xantia I've never been entirely happy with the performance of the front brakes. (compared to two other Xantia's I have access to which have pin sharp brakes, let alone the GS's and CX's etc that I've driven or owned in the past)

I've done all the usual things to them - new good quality pads, lubricated the calipers, bled them, etc, and everything checks out fine, but they just aren't as sensitive as they should be.

To be clear - hard emergency braking is fine, I can easily trigger the ABS and do a respectable crash stop. What isn't fine is light to medium braking.

I've noticed two related symptoms - one is that after a few days of lack of use the sensitivity to light braking gets even worse to the point where you have to press moderately hard to stop the car against the automatic transmition at traffic lights.

If I go for a brisk drive and apply the brakes hard a few times suddenly the sensitivity for light braking returns to about 80-90% of what I would consider normal but the effect always wears off after a few hours. The new pads have been in over 6 months now so I doubt there are still any bedding in issues.

The other thing I notice is that when first driving the car after a couple of days at the same time that the brake sensitivity is poorer, the pedal seems a bit softer than normal, but if I pump the pedal hard a few times it seems to get stiffer and feel more like a normal stiff Citroen brake pedal.

(Yes, it long ago had the "silly spring" removed so the pedal SHOULD feel stiff)

Until recently I was leaning towards it being due to the front discs being slightly curved, (causing incomplete pad contact for light brake pressures) but now another possibility has occured to me - what if one or both of the front brake hoses have perished and are starting to internally collapse ?

This is not an uncommon problem on some cars, although I havn't heard of it on the Xantia before. Could the inside of the hose be partially collapsing at the bends in the hose when the car is resting, causing the hose to have to expand again when pressure is applied ?

(Thus slowing the brake response and losing the sharp edge the brakes should normally have)

Another clue is that when I got the car the hydraulic system had RED oil in it, so without knowing what that oil was, it could potentially be something that could damge the hoses......

Any ideas ? I'm assuming the hoses are relatively easy to replace ? Are they expensive ? If they're not I might just replace them and see what happens as I've basically done every other thing possible to the front brakes short of replacing the discs...

Regards,
Simon

AndersDK · Unread post by **AndersDK** » 13 Jun 2006, 22:50

bet the red oil was ATF -

Never heard that the front brake hoses could do this. They will rot externally long before they start doing funny things internally - if ever.

Note that you cannot pump the brakes on a hydroCit. It just feels like it.
Its fairly easy to understand as you know yourself that the master valve is not a brake valve - but a regulated "tap" to dose the pressure fed to the brakes. Hence the name doseur valve.

What happens when you pump the pedal is that you in fact adjust the handbrake mechanism - which brings the piston and pads as far out as possible.
Wether you believe it or not I'm convinced you have air in the brakes.

This does not give spongy pedal as in normal cars - but an effective delay in brakes from you press the pedal. As you dont get a satisfactory feedback on your pedal foot - you promptly and pr backbone press harder. This gives you the impression that your Xantia brakes are getting harder and less sensitive.

You should bleed both front calipers for long time using a PVC hose to bleed back directly to the reservoir. This way you rather flush the brakes than bleeding them.

If you still have a problem then try overhauling the doseur valve.
- and yes I know its located insanely on a RHD vehicle

As someone here said before : hours of entertainment

Amazon Activa · Unread post by **Amazon Activa** » 13 Jun 2006, 23:01

Is the red stuff the cleaning fluid?

bxbodger · Unread post by **bxbodger** » 14 Jun 2006, 00:04

It's most unlikely to be a problem with the doseur- it is, after all, only a valve with a limited range of movement.

You mention a pad change but not discs- when I had similar vagueness in the front brakes with a very short and disconcerting delay, it was cured by changing pads and discs together.

There was a small wear ridge on the discs, which I think got in the way of the pads hitting the discs square on and quickly.

It wasn't a lot of wear, on a normally braked car I'd have left it longer, but the BX most definately didn't like it!!

And, yes, I needlessly changed the doseur in an effort to sort the problem

- the wear ridge on the discs just didn't seem big enough to cause any problems........

Mandrake · Unread post by **Mandrake** » 14 Jun 2006, 01:05

AndersDK wrote:bet the red oil was ATF -

Yes I bet so too... but I wonder what kind... (Dex II, Dex III etc)

Never heard that the front brake hoses could do this. They will rot externally long before they start doing funny things internally - if ever.

Internal collapse of brake hoses is a known problem, although not very common - a friend of mine recently had it happen on a Honda, although the usual symptom is of brakes that wont release properly.

A brake hose has two layers with a reinforcing webbing between them to prevent the hose from collapsing the hole inside when the hose bends, but sometimes the inner layer delaminates from the webbing and outer layer.

This can cause the hole to get blocked even though the hose looks fine from the outside. When you apply the brakes the pressure stretches the hole open but when you release them the hole can close again.

Note that you cannot pump the brakes on a hydroCit. It just feels like it.
Its fairly easy to understand as you know yourself that the master valve is not a brake valve - but a regulated "tap" to dose the pressure fed to the brakes. Hence the name doseur valve.

Yep, aware of all that

By pumping the brakes I'm simply saying that I'm fully depressing the pedal a few times...

What happens when you pump the pedal is that you in fact adjust the handbrake mechanism - which brings the piston and pads as far out as possible.

I don't think this is whats happening, because the handbrake self adjuster will only need to advance one click every few months as the pads wear, the phenomina I'm talking about happens every day.

Almost every day the brakes start off being insensitive for light applications, and after a few hard brake operations it becomes sensitive again.

Wether you believe it or not I'm convinced you have air in the brakes.

I'd like to believe it

But unfortunately I've bled the brakes on several occasions now with no improvement, although not recently, so I might try it one more time.

This does not give spongy pedal as in normal cars - but an effective delay in brakes from you press the pedal. As you dont get a satisfactory feedback on your pedal foot - you promptly and pr backbone press harder. This gives you the impression that your Xantia brakes are getting harder and less sensitive.

But you see that is opposite to what I'm getting - I *do* get a softer pedal, but I *dont* get any delay in brake operation, only a lack of sharpness and sensitivity.

You should bleed both front calipers for long time using a PVC hose to bleed back directly to the reservoir. This way you rather flush the brakes than bleeding them.

I will give it a try but I don't hold out much hope, as I said I've been pretty thorough in the work I've done on the brakes and bleeding was one of the very first things I did...

If you still have a problem then try overhauling the doseur valve.
- and yes I know its located insanely on a RHD vehicle
As someone here said before : hours of entertainment

Yeah, isn't it in a stupid place...

I highly doubt there is a problem with the doseur valve though, so I won't be touching that...

Regards,
Simon

Mandrake · Unread post by **Mandrake** » 14 Jun 2006, 01:08

bxbodger wrote:It's most unlikely to be a problem with the doseur- it is, after all, only a valve with a limited range of movement.

You mention a pad change but not discs- when I had similar vagueness in the front brakes with a very short and disconcerting delay, it was cured by changing pads and discs together.

Yeah discs is my other suspected possibility, if the surface of the disc is not perfectly flat the pad will only touch over a small surface area with light brake pressure, and its not until you press hard that it will "squeeze" the surface of the pad into the shape of the disc and give full contact.

There was a small wear ridge on the discs, which I think got in the way of the pads hitting the discs square on and quickly.

Where was the ridge ? At the edges or in the middle of the swept area ?

It's normal for a ridge to form at the edge of the disc where the pad isn't wearing the disc, but you can just chamfer the pads slightly to get around that. If the ridge is in the middle of the swept area its more troublesome though.

Regards,
Simon

Allanxantia · Unread post by **Allanxantia** » 14 Jun 2006, 09:28

this sounds very like glazed pads to me. I have had this problem a number of times on my Impreza. If you drive enthusiastically and overheat the brakes the pads can glaze over and give very poor performance, until they get hot that is. Best solution is to remove the pads and give the friction surface a good going over with a wire brush. If you are going to be hard on the brakes then swap them for EBC red stuff ceramic pads. It's got to be worth a try

Mandrake · Unread post by **Mandrake** » 14 Jun 2006, 10:08

Allanxantia wrote:this sounds very like glazed pads to me. I have had this problem a number of times on my Impreza. If you drive enthusiastically and overheat the brakes the pads can glaze over and give very poor performance, until they get hot that is. Best solution is to remove the pads and give the friction surface a good going over with a wire brush. If you are going to be hard on the brakes then swap them for EBC red stuff ceramic pads. It's got to be worth a try

Hi,

Yes it does behave a lot like glazed pads, but I don't think thats it either.

The whole reason for replacing the pads in the first place was the problem I describe, (they had plenty of thickness left, although they were an el-cheapo brand) and although the overall braking improved quite a bit with the new pads the basic problem of light braking sensitivity (especially after lack of use) remained.

I was also very careful to bed them in properly without overheating them, and I've checked them since a couple of times for signs of glazing and there isn't any...(I'm seldom heavy on the brakes - after all its a 2 litre automatic

)

Of all the cars I've had over the years and all the Citroen's I've driven/dealt with for that matter, I've never encountered a problem quite like this that stubbonly refuses to go away despite going over nearly every possibility....

Regards,
Simon

Unread post by **RichardW** » 14 Jun 2006, 10:30

"I was also very careful to bed them in properly without overheating them"

I once read a description of bedding in brake pads that suggested this was completely the wrong way to do it, and in fact you should work them hard from the off - right up to and beyond the point where they smoke

I'll try and find it later....

"I'm seldom heavy on the brakes "

This could be part of your problem - you need to work Xantia brakes quite hard to keep them in top order I find. If you do a few hard braking runs you should find the brakes work much better - my Dad always used to have to do this to hydraulic cits when Mum had been driving them - gently!

Your symptoms do suggest that you are needing to get the brakes warmed up to make them work - perhaps the callipers are a bit sticky. What pads are you using? It's possible that a change of discs is in order to get smooth surface vs the pads - sometimes new pads do not settle on old scored discs (especially now they're so hard).

Mandrake · Unread post by **Mandrake** » 14 Jun 2006, 10:56

RichardW wrote:"I was also very careful to bed them in properly without overheating them"

I once read a description of bedding in brake pads that suggested this was completely the wrong way to do it, and in fact you should work them hard from the off - right up to and beyond the point where they smoke I'll try and find it later....

Yeah, I think I've read that article.... unfortunately any time that I've bed in new brake pads a bit to "enthusiatically" in the past it inevitably ends up with glazed pads which need resurfacing and bedding in a second time....too light or too hard during bedding in can cause problems...

I think the answer to good bedding in is to apply the brakes fairly hard but not too many times in a row so they don't get too hot...

"I'm seldom heavy on the brakes "

This could be part of your problem - you need to work Xantia brakes quite hard to keep them in top order I find. If you do a few hard braking runs you should find the brakes work much better - my Dad always used to have to do this to hydraulic cits when Mum had been driving them - gently!

When I say I'm not heavy on the brakes I mean not compared to someone who drives an Impreza

Also bear in mind that I've already pointed out that the brakes DO improve in sensitivity a lot if I give them a few good hard bites, but the problem is that they very quickly return to being insensitive again - usually by the next day. THAT is the part that is not normal.

Your symptoms do suggest that you are needing to get the brakes warmed up to make them work - perhaps the callipers are a bit sticky. What pads are you using?

Umm... its about 9 months ago that I bought them so I'm not 100% sure without checking receipts but I think they're Mintex.

It's possible that a change of discs is in order to get smooth surface vs the pads - sometimes new pads do not settle on old scored discs (especially now they're so hard).

Yeah, I'm sure that the discs could be better...they have typical signs of wear on them, nothing excessive, but then again so do the discs on the other two Xantia's which have nice sensitive brakes.

I'm kind of shocked at how quickly the discs seem to wear out on the Xantia (going by other forum correspondants experiences) as back in the days of GS's etc, replacing the discs was unheard of... my GS was 20 when I sold it and it still had the original discs in good condition and the brakes were terrific....

Regards,
Simon

bxbodger · Unread post by **bxbodger** » 14 Jun 2006, 11:39

Discs wear out quickly now because the pad material has changed to get rid of the asbestos- discs did indeed last the lifetime of a car, and it was very unusual to need to change them up until the late 80's. It's now the discs as well as the pads that are sacrificial, and they should really be seen as disposable service parts......

My wear ridge was at the outer edge of the discs, but they were a bit groovy all over as well, and changing pads and discs as a set did cure the brake dalay problem- it's very unnerving, even though it's only for a split second!!

Modern pad materials are pretty good straight out of the box, and I don't think you need to do much, if anything, in the way of bedding them in now.

I reckon a pad'n'disc change will fix it- but of course I'm speaking from a UK perspective. Here in the UK they're cheap bits- the equivelant of a good night out in the pub but where you are it may be a different story!!

jeremy · Unread post by **jeremy** » 14 Jun 2006, 14:21

I did have considerable problems with our ZX when I changed the pads. Discs didn't look brilliant but no-where bad enough to change so I just put in new pads. Brakes were poor but I wasn't really sure why - and also had never driven another ZX which means I didn't know what to expect. When trying to bed them in i got some wonderful smells but no real improvement.

When I eventually replaced both discs and pads I found the reason - the new pads I'd fitted covered quite a large additional area of the disc at the centre (1/4 inch). This part of the disc had been rough and although after 10,000 miles or more the rust had been smooth off if was still clearly visible as a raised strip of rusty metal.

I know I could have cut the pad back or polished the raised bit off (probably have taken a grinder) I replaced both discs and pads as I had them there. Brakes were immediately much better.

So I wonder - do you have something similar? I think a lip on the outside edge may not be such a problem but for some reason the centre bit just wouldn't wear.

Incidentally this ZX has Bendix brakes - just like a BX (and Xantia?) but without the handbrake.