How bad is bad... Brakes.

[RugbyPete]

I replaced the pads on my xantia td yesterday in the hope it would combat my bad braking distances, but found when i took the old ones off they were only half worn.

They were very smooth though and so were the discs. The discs were worn compared to the outer edge showing what they were like new.

Now, should i be looking at hydraulic causes or do I need to replaced the discs ( i will anyway soon, but is this the cause?)

The brake pedal barely moved when pressed and doesnt affect braking much at hugh speed. At 10mph it will stop the car ok, but from 40mph+ I need to anticipate and engine brake to take the strain off my brakes lack of ability.

How can i trouleshoot further - if hydraulic what else would i look for (power steering is ok for example), i didnt think worn discs with new pads would mak braking thi useless.

Thanks

[slim123]

Hi Pete.

I guess that you have looked at the front brakes??

Do the lot, front and rear.

Fronts, don't stop at replacing the pads, take the pads out again and this time check that the sliding part of the caliper is free, you should be able to slide tha caliper back and forth with ease, if not a quick clean should sort it.
Also check that when you fit the pads, they go in easy, if not get a small file and wire brush, then clean all the crud out of the groves where the pads sit.

Rears, Take out the pads and give the calipers a real good clean up, untill the pads go back in again without having to force them in, any more than a gentle push with one finger and it aint clean enough.
Then put the pin bolt back through the caliper wthout the pads in and do it up snug, now you can remove the two 17mm bolts holding the caliper to the car and remove the caliper without loosing any fluid or introducing any air. Next gently move the caliper to one side, still connected to the brake pipe and scrape all of the flakey corrosion fron the face of the arm and the back of the caliper, give it all a good wire brushing for a final clean. Now you need to wipe a smear of grease up the facing part of the suspension arm, where the caliper sits, put the caliper back on and remove the pin bolt, now put the pads back in and the job is sorted.

If I was a gambler, I would bet that this woud increase the braking efficiency of your Xantia a lot.

Regards
Slim.

[citronut]

dose it lock the brakes up when you press the pedel hard, if so it might be the (light ) first presure on the pedel is not working due to air in the system, if this is so bleed the brakes all round
regards malcolm

[wrinklet1]

When you replaced the brake pads on the front, did you also re adjust the handbrake cable and check it for locking on when turning a bend? If the brakes are contacting you may find them too hot to do any braking??
Also, Slim123 is correct you do need to do a bit of maintainence work on the caliper pistons, namely, wind them back and spray brake cleaner to clean and lubricate.
Doubtful about it being air in the system, BUT give it a go anyway, nothing lost and it clears any crud from the pipes.

Paul

[RugbyPete]

Picking up some discs on friday from german and swedish, they'r eonly 20 quid. A sthe handbrake stops the car int he same fashion
Im guessing its got to be a lack of friction thing. I doubt its cos they are hot because the braking is bad on the coldest day right from startup

The piston moved ok and the caliper slides freely back and forth.
the handbrake also moved, although i couldnt remove the offside as the plastic lug had wedged into the small arm on the caliper making impossible to shift.

I'll get the discs first and go from there

[Monkeyfeet]

A xantia with brakes duff brakes....?
I've changed fr discs/pads before simply because the discs were worn, never bothered too hard to clean the callipers. I had always been able to lock up the wheels without much pedal pressure at all.
Also removed the spring inside the pedal to 'button' linkage - that helped with brake feel a lot.
It just that's there's so much pressure to work the brakes, could it be more than calliper corrosion?

[rowanmoor]

Could it be a stuck/jammed doser valve or similar? Taking the silly spring (that is the spring Monkeyfeet just mentioned - there are a few threads here about it) out may show that up - if it is stuck you would get even less movement of the peddle than normal for a non-sprung peddle.

In case you don't know, the doser valve is the bit the brake peddle is connected to. The peddle pushes on that and it allows the pressure into the brake lines.

[citronut]

how did you get the pistons back when you replaced the pad, i hope you wound them back, otherwise you will stip the conical thread inside the piston, then they wont adjust back up
regards macolm

[RugbyPete]

I wound it back as per reocmmended advice. They went in a lot easier than i was expecting, its quite dry dusty and orrible down there by the brakes.

braking has improved since putting pads on but its still like 1950's car with drum brakes on

I'm hoping the discs are just all too smooth and worn

[RugbyPete]

Sounds exactly like the problem i have with my Xantia (95N TD SX). Braking is a pain in the proverbial. The car's had new front / rear disk/ all round and still the braking distances are really poor, the brakes have absolutely no feel to them. So bad that, as you say i need to 'plan' any stops, hardly ideal. I've convinced myself that i need a fluid change and that's the next job. Brakes on my BX TD were absolutely spot-on, i've had this car a while now and it's been getting gradually worse. Keeping an eye on this thread closely ... hope you can get it sorted eh!

Could do with comparing portfolios! (OR carfolios!)

Have you had any other work done? ie. caliper overhauls or spheres replaced, history of fluid leaks or really worn discs+pads?

[citronut]

another idea it could be the front brake flexi hoses are colapsing, this would severly impare the braking efort,

i very much doubt new discs will fix this problem as hydraulic citroens have far more power on there brakes than conventional braking systems

regards malcolm

[Stempy]

I'll be keeping an eye on this thread too as my brakes have a decidedly wooden feel If I find a solution I'll post it up. Would the doseur valve be a suspect?

[Mandrake]

Count me in on this thread - the brakes on my Xantia have never been up to snuff compared to our two other Xantia's. (Or any other Citroen for that matter)

When I first test drove the car I wondered if they would even stop the car at a stop light!

The things that I have done to improve the brakes in the two years I've had it:

* Removed "silly spring" in the pedal unit - big improvement
* New pads all around, and free up rear calipers - quite significant improvement
* New front discs - some improvement, but not a lot - the originals were badly worn though, slightly warped, and had high lips so were due to be replaced. Rear discs need replacing too.
* 3 LHM changes to flush out "incorrect" oil that was in the system. (red - ATF ?)

After that I would call the brakes "OK", but they are not sharp and sensitive like the other two Xantia's. Emergency braking when pressing the pedal hard is fairly good, the problem is that the pedal effort to get a certain level of braking is much higher than it should be, leading to light to medium braking feeling "dull" and insensitive.

Other things I notice are that a bit of hard braking will temporarily improve the sensitivity and sharpness quite dramatically - almost to normal levels, but the effect fades away in a few hours.

I also notice that the handbrake in my car is excellent - and in fact much better than either of the other two Xantia's which have worse hand brakes but better footbrake action - mine is the only one of the three which has had new front pads.

Since the handbrake operates on the front pads and works so well, it leads me to believe that *mechanically* the front calipers/pads/discs are in good order, (or the handbrake would be poor too) and that there is a hydraulic fault.

After the things that I have already done to the hydraulics, that leaves only two things I can think of:

* Faulty brake doseur valve, or
* Faulty/collapsed front brake hoses to the calipers.

I'm leaning towards the latter, and wondering if the "ATF" that was in the system before I got it could have damaged the hoses internally ?

Has anyone chased insensitive Xantia brakes and managed to fix it by replacing either the doseur valve (expensive) or the caliper brake hoses ? (relatively cheap)

Also, both the cars with good brakes are early models - 1993 and 1994, mine is a 1997 - were any changes made to the sensitivity of the brake doseur valves in later years ? If there were, I havn't seen any information about it.

After 2 years of mediocre brakes on a car that should have excellent brakes, I'd quite like to get to the bottom of it.

PS - when stopping at traffic lights the rear suspension tends to be compressed quite a lot by the braking action - which suggests that the rear brakes are doing more than their usual percentage of work under light braking, and that the problem is most likely only with the front brakes.

PPS - the front caliper slides have been lubricated - no noticable change.

Regards,
Simon

[CitroJim]

Count me in on this thread - the brakes on my Xantia have never been up to snuff compared to our two other Xantia's.

Same here Simon, having three of them, a comparison is just too easy.

My early (sinking) Mk1 1.9 TD has very satisfactory brakes without the spring, my Mk 1 2.1TD has excellent brakes even with the spring still fitted and my Activa (MK2) lives in a world of it's very own as far as the brakes go. They're far from the standard reached by my other two Xantias. They exhibit all the same symptoms as yours and I've done most of what you've done to try and improve matters significantly.

My other symptom, and this is disturbing, is a small delay on first application after the car has been standing for a week or so. The only sphere I've not replaced on this car is the anti-sink and I'm wondering if it's leaking a bit of nitrogen although every time I've bled the brakes no significant air comes out.

I'd say they were OK but not outstanding as they should be.

The only thing I've not done is replace the flexis but it is so cheap and easy to do, it's worth it just to see.

My Activa once had a very leaky dosuer valve as when I first had it, the drivers footwell was full of very elderly LHM that had eaten into the sound deadening stuck to the floor. It was an old wound and has never returned in my ownership but a nagging suspicion still hangs over the dosuer...

In all other hydraulic departments, my Activa is almost perfect, with a tick rate measured in decades...

Is this a perculiarity of Hydractive cars perhaps?

[Mandrake]

Count me in on this thread - the brakes on my Xantia have never been up to snuff compared to our two other Xantia's.

Same here Simon, having three of them, a comparison is just too easy.

My early (sinking) Mk1 1.9 TD has very satisfactory brakes without the spring, my Mk 1 2.1TD has excellent brakes even with the spring still fitted and my Activa (MK2) lives in a world of it's very own as far as the brakes go. They're far from the standard reached by my other two Xantias. They exhibit all the same symptoms as yours and I've done most of what you've done to try and improve matters significantly.

Hi Jim

Sorry to hear that - maybe if a few of us on the forum put our heads together we can get to the bottom of it!

My other symptom, and this is disturbing, is a small delay on first application after the car has been standing for a week or so.

Yes, I have had this too, although it hasn't been so obvious in recent times, except in my case even standing for a day or so is enough.

The first time I try to apply the brakes moderately hard after the car has been standing a day or two, they just feel dead, and I have to press quite hard to stop at a stop sign.

(This is not helped by the fact that its an automatic and occasionally the engine tries to idle too fast, which means the brakes have to fight the automatic)

Now heres the thing - if, before I drive off, I fully depress the brake pedal a couple of times while stationary, when I go to stop the first time at a stop sign, the brakes are a lot more sensitive than they would have otherwise been.

The only sphere I've not replaced on this car is the anti-sink and I'm wondering if it's leaking a bit of nitrogen although every time I've bled the brakes no significant air comes out.

When they leak nitrogen (just before failing completely) you'll find significant amounts of "air" in the rear brakes each time you bleed them - this happened on Dad's car, where I bled them several times over 4-5 months and every time there was quite significant amounts of air, especially on the right hand side.

If the sphere is totally punctured (as mine was) you won't get any air. I replaced my anti-sink sphere about a year ago, going from punctured to new, and it made a tiny improvement to the brakes (the rear brakes obviously) but didn't fix the problem.

I'd say they were OK but not outstanding as they should be.

The only thing I've not done is replace the flexis but it is so cheap and easy to do, it's worth it just to see.

I don't suppose you'd be willing to do so and report back to us then ?

I have seriously considered changing mine, but here in NZ that means ordering them overseas from GSF if I wan't to get any kind of half decent price - but if I thought there was a reasonable chance it would fix it, I would do so.

My Activa once had a very leaky dosuer valve as when I first had it, the drivers footwell was full of very elderly LHM that had eaten into the sound deadening stuck to the floor. It was an old wound and has never returned in my ownership but a nagging suspicion still hangs over the dosuer...

In all other hydraulic departments, my Activa is almost perfect, with a tick rate measured in decades...

Is this a perculiarity of Hydractive cars perhaps?

Can't see how - although my car is Hydractive and the other two aren't.

Mine has ABS - one of the other two has ABS and the other one doesn't, so there doesn't seem to be any correlation with ABS.

Heres my theory - the front flexible brake hoses have delaminated and collapsed inside, partly or largely blocking the flow, and when they sit for a while unused they collapse, and then when you apply the brakes hard the pressure effectively "blows them up" inside like a balloon, temporarily restoring the internal hole diameter.

If you think about it, to get "sharp" braking response, its imperative that the brake lines that are carrying the pressure to the brakes are fairly "rigid" and don't change in internal volume with pressure so that pressure change is transmited instantly - if the hoses are internally collapsing and blowing up like a balloon every time you apply the brakes, this would cause delay much like having air in the lines - except instead of having no brakes at all for a moment then full braking as you would with air, it would cause the braking to apply immediately, but only gradually reaching full strength as the hose swells - giving a lack of sharp response.

As I mentioned, 2-3 emergency stops and the brakes suddenly become rather sharp and responsive to light braking again, for a while, which could be attributed to pad/disc surfaces or sticky calipers EXCEPT I get much the same effect from pumping the pedal hard just before setting off, when the car is stationary and the brakes are cold - which would rule out pad surfaces etc.

And the handbrake is always good - I can stop the car from 50Km/hr going down a 1/3 incline in about 10 seconds - slow compared to a foot brake, but quite impressive for a hand brake - so surely it is a hydraulic problem...

Regards,
Simon