more suspension weirdness

[deian]

Hi, me again

Today the hydraulics on my car is weird.... again, the delay in braking has come back, which was fixed untill it happened again this time, and on top of this the rear suspension is bouncing up when i the brakes hold, even when lightly, harder you brake higher it goes, now 'what' on earth is going on?

This seems weird behaviour to me, ok you will slate me for not bleeding brakes or changing lhm like i said i would but i will get round to it, can they be related at all,

(on a another post 'V6 Xantia #2' AndersDK locked it cos of my careless words, i want to apologise to 'all' for my breaking of the rules there and spoiling it, i will behave in future , just goes to show that AndersDK is indeed good at his job as admin guy)

Thanks guys

[Peter.N.]

The rear section of the brake valve is fed from the rear suspension so that as the load increases the fluid pressure rises and increases the braking effort on the rear wheels. It sounds as though the problem might be something to do with the brake valve. If it is allowing an excessive ammount of fluid to leave the rear suspension, the height corrector will compensate by allowing more fluid in, which would cause the suspension to rise. Thats the theory! whether the valve could leak enough to cause this effect, I'm not sure, but I'm sure someone will tell you.

[jgra1]

I have the same problem, Deian

It seems a brake bleed could be needed from responses I have read..

J

I will follow up the mysterisou SE thing and let you know

[Mandrake]

Hi, me again

Today the hydraulics on my car is weird.... again, the delay in braking has come back, which was fixed untill it happened again this time, and on top of this the rear suspension is bouncing up when i the brakes hold, even when lightly, harder you brake higher it goes, now 'what' on earth is going on?

This seems weird behaviour to me, ok you will slate me for not bleeding brakes or changing lhm like i said i would but i will get round to it, can they be related at all,

So you havn't bled the rear brakes at all yet ? If not thats almost certainly the cause. Air in the rear brakes will cause both a delay in the braking response, and the back to lift violently when braking hard.

Get cracking and bleed those rear brakes, its an easy job.

If you have bled the rear brakes before, and it fixed the problem, and now it has returned, it means that "air" is getting into the system somehow. This is either nitrogen bubbling from a faulty or about to fail sphere, or the dreaded suction leak issues with the pump / pump hose.

I think my Dad's car has a failed anti-sink sphere which is bubbling nitrogen into the rear suspension/brakes, as the brakes were bled thoroughly 3 months ago, then a few weeks ago I noticed it was lifting at the back and had brake delay, so I bled them again and got LOADS of air out of them, and the brakes behaved again (MUCH better braking, with hardly any lift at the back) but then only 3 weeks later the same problem has returned.

My guess is the anti-sink sphere is the original (11 years old) and has gone kaput, bubbling its remaining nitrogen into the system...(it could also be the accumulator, but that would also tend to affect the front brakes, which don't seem to have any problem, and the rear suspension spheres are 6 months old so I doubt its them)

Regards,
Simon

[jeremy]

Simon - can't you clear gas from a leaky sphere by 'Citroebics?' - Its only necessary to bleed from the brakes if the gas has got into the limbs going to the brakes themselves - and as the movement in this part of the circuit should be minimal and it returns when the brakes are released, circulating the fluid by 'Citroebics' should clear the gas.

One of the advantages of a BX or Xantia without anti-sink! - I suppose your father could drop the car when he's finished with it and see if the problem goes away! - much more 'Citroen - like.'

[Mandrake]

Simon - can't you clear gas from a leaky sphere by 'Citroebics?' - Its only necessary to bleed from the brakes if the gas has got into the limbs going to the brakes themselves - and as the movement in this part of the circuit should be minimal and it returns when the brakes are released, circulating the fluid by 'Citroebics' should clear the gas.

Hi Jeremy,

One would think so, and yet here it is again with lots of air in the brake lines, again. I suppose once any air bubbles in the rear suspension traveled past the junction where it splits off to head towards the brake doseur valve its a one way journey and it will stay in the brakes regardless of Citroerobics.

Whatever the reason is, it's happening...

What puzzled me is that both times when I bled it there was LOTS of air right at the very end of the lines - eg, most of the bubbles came out before any significant amount of oil. I have no idea how the air could get so far down the line....

Regards,
Simon

[deian]

simon.... and all...

i did some priming today.... lowered the car, open the bleed valve, looked into the lhm resevoir.... and i've seen some bubbles before but this was like a can of beer being opened after been shaken, it was bubbles like there was no tomorrow, didn't stop for a long time, brakes are still delayed, not much difference, but so much air?? i tend to think one of the rear spheres has leaked big time? any pointers?

thanks

[AndersDK]

Get those rear brakes bled now

You are chasing shadows mate !

[Mandrake]

simon.... and all...

i did some priming today.... lowered the car, open the bleed valve, looked into the lhm resevoir.... and i've seen some bubbles before but this was like a can of beer being opened after been shaken, it was bubbles like there was no tomorrow, didn't stop for a long time, brakes are still delayed, not much difference, but so much air?? i tend to think one of the rear spheres has leaked big time? any pointers?

thanks

Hmmmmm.......

Did you notice the bubbling in the tank after just lowering the suspension, or was it not until you opened the regulator bleed screw that you saw it ?

To actually see frothing in the surface of the oil in the tank requires a LOT of emulsified air bubbles, due to the way the returning oil arrives inside one of the filters and can only gradually difuse out into the main tank.

The smaller amount of air bubbles/leak that I'm chasing on my car is not enough to cause visible frothing in the tank surface...

I agree with Anders too - stop ducking and dodging and bleed those rear brakes If nothing else it will give us some information as to what might be going on...and anyway, lowering the suspension and/or opening the regulator bleed screw will do nothing to bleed the brake lines...(since they're dead ends)

If you've got frothing going on in the tank then trying the clear section of return hose as I showed in a recent picture may help you find out where it is coming from. (By observing WHEN bubbles go by as you do various things such as lowering the suspension etc)

Edit: Waaaaaait a minute.... when you say you've "done some priming" do you mean you disconnected the hose from the resoviour to the pump ? If the answer to this is yes then you will get frothing in the tank for a few minutes after that because you inevitably get a bunch of air in when disconnecting the hose.

The only time you would ever do this is if the pump wont pump at all because it's lost its prime. Definately not something you would do when trying to bleed the system...(maybe I've misunderstood you)

Regards,
Simon

[deian]

no no, not taken any pipes off, but there was mad frothing, when i lowered and open the bleed valve (i belive this helpt to more fully depressurise the system).

So yes, saturday job is to bleed the rear brakes. A MUST DO JOB, and some pipes to bypass the pipe u talk about, i'll see which one it is when i find the post. Then I'll do some 'tests'.

Thanks guys! If the frothing happens again I will take pics for you.