1998 Citroen Xantia 1.9td spongy braking!

[avamotor]

right then FCF, thank you for the updates, I have been out and swapped the rear dics and pads this afternoon and rebled the rear calipers again (how was i to know that the caliper falls in half! )

DickieG you were correct, I had to carefully remove the corrosion off the rear of the calipers and with the exception of shearing off the disc retaining peg, the first side took an hour and half to put on correctly and the other side took 35 minutes (experienced now!!!! ).

I then bled rear calipers free from air and on bleeding, the clicks were every second or so, on tightening up the clicks then ran to approximatley 20-30 seconds.

I refitted the road wheels lowered it off the axle stands, set the height to normal and checked the level, all appears well with no leaks. I took it for a run but do understand that I have to allow the rear brakes to bed in before i can expect any kind of effecientcy so its still early days yet but again when I tried the brakes, it was still no different, I suppose it may be a case of waiting to get used this car (but my other Citroen Xantia Exclusive 1998 1.9td, when the automatic gearbox was working, had perfect working brakes although the exclusive also has abs).

so having tried all this, with no air trapped in the system, is it time to try the pedal adaption mod to see if this improves the situation for me, also what length of rigid 15mm pipe do i need to cut to do a job for test purposes?

Thank you so far for the advice, still learning by the minute!

look forward to any more advice your willing to give. Garry

[Xaccers]

Regulator tick rate of 20-30 seconds is indicative of a flat accumulator sphere, and I would suggest that the rear accumulator (known as the anti-sink sphere) is also likely to be flat.
I'd get them changed.
I cannot see how the spring can give spongy braking despite what Richard says. The spring is too chunky and stiff to be like that.
The flexible brake pipes on the front callipers do tend to need changing at 10-15 years, so it may be worth getting them checked.

[avamotor]

okay thank you for clarifying that, so if i pick up a new accumulator sphere today, this replaces the the sphere at the front of the engine near the gearbox/engine. what is the safe and correct method for changing it?

do I set it the level between high and low a few times and finally leave on high as suggested by Haynes for brake bleeding? axle stands under the car and with the engine running undo the pressure release bolt 1 turn and then remove my green paperweight?

installation reversal of above? will i need to bleed all the brakes again?

[xantia_v6]

Just a thought... I had a Xantia to which someone had fitted pads with very hard friction material, and it made the brakes feel quite ineffective and the pedal quite spongy compared to normal Xantia brakes.

[jgra1]

Me doing my rear discs and pads tomorrow.. Must admit I have never done them on a xant.. thanks for the caliper tip Gaz..

Re acc sphere.. I think.. get car on low, but with axle stands under the front. Then undo the 12mm headed bolt - 1/2 a turn only (bolt is the only 12mm, sits on the front of the pressure unit, that the sphere also screws into) This will release pressure back into the system. Then away you go unspinning the sphere with whatever means at your disposal.

Take note of the small seal when putting new sphere on (make sure old seal is out as well) - hand tight, job done

John

[Xaccers]

okay thank you for clarifying that, so if i pick up a new accumulator sphere today, this replaces the the sphere at the front of the engine near the gearbox/engine. what is the safe and correct method for changing it?

do I set it the level between high and low a few times and finally leave on high as suggested by Haynes for brake bleeding? axle stands under the car and with the engine running undo the pressure release bolt 1 turn and then remove my green paperweight?

installation reversal of above? will i need to bleed all the brakes again?

For the front accumulator, as jgra says, car on high, axle stands under the front jacking points (jack on the subframe if you need to raise the car a little bit more to get the stands under, I aim for the large nut behind the wheel arch), height on low, the back will drop raising the front and giving you plenty of space to work under safely.
Let the car settle, undo the bleed screw no more than 1/2 a turn (do not take it out!) to de-pressurise the system, then turn the engine off, nip up the bleed screw, and unscrew the accumulator sphere. You may get lucky and be able to use a large chain/strap wrench, otherwise you'll need a sphere tool, either home made (see the link in my signature) or one from ebay, or the best one from Pleiades.
The new sphere will come with a new O-ring, coat it in fresh LHM and fit it into the recess in the sphere socket, then screw the sphere finger tight.
Start the car up, get it on high, move the axle stands to the back jacking points, set the car on low, de-pressurise, stop the engine.
In front of the spare wheel, screwed into a cross beam is the anti-sink sphere. Unlike the other spheres you have, the hydraulic pipe screws straight into the sphere.
Use a 9mm flare spanner to get the pipe nut going, then hang the spanner on the nut and screw the sphere out.
You'll also need a 4.5mm pipe seal, which GSF sell, although you may be able to re-use the seal which is probably still inside the removed sphere, be careful extracting it if you're going to re-use it.
To fit the new anti-sink sphere, even though there is no recess for it, still use the new O-ring as it will help stop the sphere rusting in place. Fit the pipe seal to the end of the pipe, don't go over the flare, and fit the pipe in the sphere, turn the nut once to get it started, then fit the sphere to it's socket again turning just enough to get it started.
Hang the 9mm flare spanner on the pipe nut again and screw the sphere home. Nip up the nut and the job's done.

[avamotor]

Hello Jgra1, Xac and other members of FCF,

Changing the rear brakes on my car 1998 1.9td sensation was fairly straighforward now i look back, the stud that sheared off the rear hub was a small imperial hex headed size but rather than be stuck waiting to track down a new/replacement unit I simply used an old cross headed treaded screw, so no locating peg for wheel but if the 4 roads cant hold the wheel on I really shouldnt be driving!!

8mm spanner at the back end of the caliper to hold the nut and 8mm ratchet to undo the bolt then allows the "tin plate" to be removed from the front of the caliper revealing the smallest brake pads in the world. I the pushed back both sides of the caliper piston using a G clamp and large screwdriver as required with the bleed screw open to allow for any pressure to be dissipated up the tube but nothing doing!

2 number 17mm bolt heads held the caliper to the back plate but 1 of the 2 was solid, so friendly pursuation using a breaker bar and WD40 helped, and because the pipe to the caliper is rigid by the time half the caliper fell apart in my hand I panicked and shouted "i didnt do it, it was already broken!" but then unpon closer inspection the rubber o ring was in good condition and I knew my caliper was'nt sat "true" against the back plate following advice in this post from DickieG, so I carefully bent the caliper roughly 90 degrees ad belted it for fun until the alloy crud fell off, followed by wire brusing the back of the caliper and then filed it true.

Cut my hands for fun!!

I then put a little copper grease on the rear of the caliper, cleaned it down and began the reversal of the above making sure the new disc went in prior to plumbing the outer section of the caliper back on (and making sure everything was perfectly clean), I was also fortunate that the old pads still had good shims so cleaned it all down, filed off the paint from the top and bottom of the new brake pads, bit of copper grease and reainstall.

Bled it all and still not fantastic brakes yet, hence the need to now swap the accumulator sphere. Collected sphere today complete with new seal and another 5 litres of LHM, so now just trying to metally build up a picture in my mind how to change the sphere.

Xac thank you for the advice, I feel that maybe I may need to call to machine mart for a chain wrench prior to getting brave!

Sorry if it sounds like a stupid question but do i have to bleed the brakes after swapping the accumulator sphere? also do i need to replace the anti sink sphere too then, i only thought i needed to replace the accumulator sphere on the front????

[Xaccers]

If you're having to buy a chain wrench I'd not do that and instead get a proper sphere tool.
The ones on ebay are ok, the best though is the tool Plaeides do.
If you've got access to an electric drill and a round lamppost then making your own tool is easy.

Whichever one you go for you tighten the loop around the sphere, use the arm of the tool to free the sphere up then remove the tool and unscrew the sphere.
There is a metal pipe that can get in the way of using the tool which is where the Plaeides and diy tools win as the the loop is off at an angle.

There is no easy test for the state of the antisink sphere while on the car, so it is best to replace it at the same time as the front accumulator.
It enables braking at the rear if the system pressure is down and the anti sink valves kick in.

No need to bleed brakes just lots of citrobics

[DickieG]

so having tried all this, with no air trapped in the system, is it time to try the pedal adaption mod to see if this improves the situation for me, also what length of rigid 15mm pipe do i need to cut to do a job for test purposes?

If you try the pedal mod it's instantly reversible and as you only need about 1 1/2" of 15mm domestic plumbing pipe so its as cheap as chips to try.

Think about the practical situation of the brake spring, the brake valve itself is spring loaded and is connected to the brake pedal via a second spring of a different rate to operate an opening valve, how on earth can pedal movement be accurately matched by the operation/opening of the brake valve? If you've ever held two springs in your hand and pressed one against the other you'll realise that expecing this arrangement to do anything other than cause random movement of the brake valve is wishful thinking in the extreme.

[avamotor]

right okay, following a break in the weather this afternoon, I legged it outdoors and swapped the front accumulation sphere care of advice from FCF and its members so thank you all and your contributions, it all went well and now all i have to do is the anti sink sphere when I get one!

I am still being very careful with brakes as a) still waiting for the rear brakes to bed in and b) still waiting to "mod the silly spring" and see if there is any improvement.

Thanks again everyone

Garry

[Xaccers]

Think about the practical situation of the brake spring, the brake valve itself is spring loaded and is connected to the brake pedal via a second spring of a different rate to operate an opening valve, how on earth can pedal movement be accurately matched by the operation/opening of the brake valve? If you've ever held two springs in your hand and pressed one against the other you'll realise that expecing this arrangement to do anything other than cause random movement of the brake valve is wishful thinking in the extreme.

When I get home tomorrow Richard I'll give you a refresher in the basic physics of non-linear springs

[jgra1]

good stuff Gaz..

I did mine today as planned.. a few details in the blog section.. think my discs may have been 160K originals