Brakes Worry !!

[tim456]

Hi all,

I bought a xantia estate a few weeks ago which I love but I have noticed a few times if I go to drive away pretty much straight after I have started the car I dont seem to have any brakes?
After 10 seconds or so its fine but as I dont know the workings of the fancy hydraulic goings on of the xantia and being the brakes is concerning, Do I have problems or is there anything I can do to rectify this please.
Many thanks...Tim

[myglaren]

Do you wait for the red STOP light on the instrument panel to extinguish before driving?

It really does mean STOP. You have to give the hydraulics time to pressurise and the Stop lamp is telling you that it is not up to pressure.
The brakes are operated from the hydraulic circuit so low pressure = no brakes.

Wait a little longer before driving off and all will be fine.

[Xaccers]

Sounds like your accumulator sphere is flat.
The fancy hydraulic goings on are thankfully very very simple
At the front of the engine there's a sphere, you should be able to see it if you look down from above.
Get the engine running and let it settle.
Listen at the front for a tick/click sound from the accumulator sphere. If it is good then there should be at least 30 seconds between ticks/clicks
A replacement one is approx £25 from GSF car parts, and chances are you'll need to replace the one at the rear of the car (up behind the spare wheel in the middle of the cross member - often refered to as the anti-sink sphere as it's fitted to cars with anti-sink valves).
They're easy to swap (damn sight easier to deal with than complicated master cylinders and newfangled metal springs).
For the accumulator, get the car up on high, put axle stands under the front jacking points (if you need to jack the car a bit more to get them in, put the jack against the subframe just behind the front wheels, i try and get the cup over the large nut), set the car on low and let the back sink right down and the front will lift up giving plenty of room to work under it. Using a 12mm spanner, open the 12mm bleed screw by the accumulator, it's the only 12mm on there and looks like a chef's hat, turn it 1/4 or 1/2 a turn and you should hear a whistle/whoosh of lhm returning to the resevoir. DO NOT REMOVE THE SCREW! It has a ball bearing behind it that works as a valve, lose the ball and you can't build up hydraulic pressure. Turn the engine off. Nip up the bleed screw.
Now, if you're lucky you should be able to unscrew the accumulator sphere by hand, but if it's rusted or has been put on by a gorilla, you'll need a tool. These are available from ebay, or Pliaedies, or make your own by following the link in my signature. A large chain/strap wrench should do the trick on the accumulator but may not be up to the task for the suspension spheres should you need to change them in the future.
So, you've loosened the sphere enough to spin it off by hand, be prepared for a douche verte. You see, in the sphere is a nitrigen filled balloon (does the work of springs on complicated other cars) and when you depressurise by putting the car on low the balloon should expand forcing all the lhm in the sphere back into the pipes.
Thing is, if the balloon has ruptured there's nothing to push the lhm out so it will be full and the lhm will run out if you hold it hole end down. Now, if the balloon is intact but very low pressure, it doesn't have enough pressure to push the lhm in it out, that is until you remove the sphere and it sprays everywhere! Thankfully it's a good hair conditioner but you wouldn't want to drink it. So just be prepared for a bit of spray.
Coat the o-ring that comes with the new sphere in fresh lhm and fit it into the recess of the sphere socket (remove the old o-ring if it's still in there).
Screw the new sphere in one hand tight.
Start the engine, wait for the red STOP light to go out, set her on high and check the lhm level. Top up if required.
Move the axle stands to the rear, set her on low, wait for her to settle down, undo the bleed screw, engine off, nip up the bleed screw.
Now for the rear, it's slightly different to the other spheres in that the feed pipe screws into the back of the sphere rather than into a socket (I know, the French are cheapskates).
So you'll need a 9mm flare spanner, and a replacement seal which I believe is 4.5mm and GSF do them too.
Slide under the car and look behind the crossmember the sphere screws into.
There's the pipe that goes to it, surrounded helpfully (not) by a box frame which stops you getting a good turn on the pipe nut.
Fit the flare spanner to the nut and get it going a bit.
Then with the spanner hanging on the nut, unscrew the sphere.
This will screw the sphere out and also off the nut (aha! thwarted those dasterly French designers!)
Again you may get a douche verte.
Even though there is no recess for the o-ring, still fit it to the sphere to stop the sphere rusting to the cross member.
Put the new seal on the end of the pipe, don't push it over the knuckle.
Screw the sphere into the socket just enough to hold it in place, and push the pipe into the sphere, turning the nut a few times (it can be tricky to get it started), then hang the spanner on the nut, spin the sphere home, nip up the nut.
Start her up, wait for the stop light to go out, get her on high and top up the lhm if required.
Let her idle on high for a few more minutes, then set her on low, let her idle down there for a few minutes and repeat (this is citrobics which gets any air/nitrogen bubbles out of the suspension system) until the kettle boils and make yourself a cup of tea.
Check the brakes.

It might be worth bleeding the brakes too (there's a thread that covers all of that), and if you're doing that anyway, as you don't know the real history of the car it could probably do with the lhm being replaced with hydroflush (total hydrorincage) for 1000 miles, then fresh lhm.

[rory_perrett]

The brakes work off the same hydraulic system as the steering and suspension. Unlike a conventional car pressing the brake pedal does not act directly on a master cylinder to provide hydraulic pressure to the brake pistons/cylinders at the wheel. On a xantia pressing the brake pedal opens a valve that lets hydraulic fluid at pressure through to the brakes. This pressure is created by the hydraulic pump (not you pressing the pedal). When you first start the car it can take some time to build up hydraulic pressure in the system. How long does your red stop light take to go out when you first start up. The front accumulator and rear anti sink spheres are there to maintain pressure in the system so this could be due to a failing, or failed, accumulator sphere. Can you hear the requlator at the front "ticking/ clicking", a rapid "tick/click" rate is another sign of a failed accumulator sphere. As cars get older, internal leaks in the system can allow pressure to leak away while the car in is standing. This is not necessarily a major problem if you don't mind waiting a few 10's of seconds before you drive off first thing as you can spend a lot of cash replacing everything to get it back up to as new performance.

Just remember if you are going to use your vehicle as a get away car,leave the engine running to maintain hydraulic pressure while you are robbing the bank.

Rory

[tim456]

Thanks for such quick detailed replies , the stop light goes out straight away as soon as the car starts every time . I could not hear the clicking at all from the accumulator I'm afraid . I've decided to replace all the spheres including accumulator and anti sink as its also a bit bouncy . I set the car on high and it seems low on the green fluid so will do that at the same time too and hopefully that will do it , I will let you know how I get on , thanks again...Tim

[myglaren]

If you are going to do that, check the colour of the LHM.
If it isn't bright green then it may be advisable to clean the reservoir & filters and treat it to some Hydroflush.

Does sound like at least the accumulator sphere is shot.