bleeding brakes xantia

jgra1 · Post by **jgra1** » 06 May 2006, 15:34

hi all i know i should check the forum for this, but just quickly, am I right?

Turn engine on, set car high, get assistant to depress brake, undo each bleed nipple in turn, starting at either back caliper, then do the front ones..

Return the fluid back into resevoir via a long tube

?

thanks
John
(have a rising rear and a pulsing pedal, have changed front central sphere)

Richard Gallagher · Post by **Richard Gallagher** » 06 May 2006, 16:21

jgra1 wrote:Turn engine on, set car high, get assistant to depress brake, undo each bleed nipple in turn, starting at either back caliper, then do the front ones..

Return the fluid back into resevoir via a long tube

Yes to the first part but in the following order, N/S/F, O/S/F, N/S/R, O/S/R, unusual I agree

Personally unless you are bleeding extensively I would discard the LHM and top up with new fluid as the brake lines are basically a 'dead end' for fluid which can be quite dirty.

fastandfurryous · Post by **fastandfurryous** » 06 May 2006, 21:38

Just to add my tuppence worth.

The initial bit of LHM is worth discarding, as it's been sat in the caliper for a while, but after the first 200cc or so, I would then use the long length of hose back to the tank and let it bleed (pump) several litres through. Not so important at the front, but at the back you can be amazed how much LHM you can bleed before a big slug of air comes out.

jgra1 · Post by **jgra1** » 10 May 2006, 22:49

guys.. i put suspension on highest , put stands under, let suspension down, removed wheels to get at bleed nipples

Put suspension back on highest....

no pressure at nipples...

ok ok i realise my mistake, no wheels no car weight no brake pressure!

so i put a jack under each hub and lifted it. On one side there was a dribble of LHM while my friend pressed pedal, on the other it was all very slow, no pressure at all.. the disks look like they havent been stopped by anything in ages ? (although car passed MOT in Feb)

ok I realise I bled for a short time, there is no difference in car (brake pulses, (and hisses) rear rises) I bled the front recently. I am happy to go and try again, but why did one caliper give no pressure and the other was lackluster?

John

AndersDK · Post by **AndersDK** » 10 May 2006, 23:17

Clearly there is a problem with the rear brakes. You can see that on the rusty rotors ...

As you used the highest setting, you then know the HC is working and then there IS in fact a high pressure in the rear suspension. Remember the height correction is overruled by the constantly supplied max system pressure to the rear suspension on high setting ...
... no matter weight load on the suspension arms or not.

I'd say you have a dodgy brake doseur (master) valve - based on all indications informed here. A bit odd as they rarely fails completely like in this instance.
Ahh... hmmm... worse

could be a sticking closed ABS rear brakes valve

In any case - a breakers visit to survive the cost it is

fastandfurryous · Post by **fastandfurryous** » 10 May 2006, 23:51

it would be worth trying this again, WITHOUT dropping to min height when removing the wheels and then back to max height.

Just put the car in max, jack it up a touch more, and then take the wheels off. The rear suspension arms should be jammed solid all the way down... you shouldn't be able to raise them without raising the back of the car.

Now jam the brake pedal down as far as it goes. Do you have pressure at the rear bleed nipples?

Mandrake · Post by **Mandrake** » 10 May 2006, 23:52

I hate to dispute our esteemed Anders here,

but it is possible for there to be no rear brake pressure when both rear wheels are hanging down unsupported, even with the height lever set to maximum - all it takes is for the manual override linkage to be out of adjustment, or the spring mechanisms which operate the height corrector to be a bit seized.

(And it seems to be more common than you would think... I can count 4-5 people on this forum who have found this problem in the last year)

This is why I always advocate keeping one rear wheel on the ground during the bleeding process - it guarentees there is weight being held up by the suspension therefore guarenteeing pressure to be available for the rear brakes.

I set the suspension fully up, then carefully jack one rear corner up just enough to get the wheel off the ground, remove that wheel, leaving the other rear wheel on the ground carrying weight. After bleeding the first side I put the wheel back on and lower the jack and repeat for the other side. Never fails.

If the discs look like the rear brakes havn't been doing any work I'd also give the caliper pistons a good workout - push them right in with a tool, then out again with the brake pedal a few times.... works wonders in freeing them up.

Regards,
Simon

AndersDK · Post by **AndersDK** » 11 May 2006, 00:34

Yeah well ...

No dispute necessary at all - thanks pointing out what I clearly missed

You cheat yourself if you try set the height to max AFTER the wheels have been removed - and the rear arms are hanging down freely. In this situation the HC has ALREADY detected the suspension in "highest position" and has the output closed. Thus the rear suspension will never be pressurised - and the panic slowly spreads all over.
To rectify : hoist the dangling rear arms with a hydraulic jack until the HC opens the pressure and starts pressing the rear arms down. WARNING : be careful - and quickly release the hydraulic jack as soon as the weight of the car shifts to the arms going down - on the jack !

OR simply remember to have the suspension in highest to remove the rear wheels - and let the height setting stay there until bleeding job is finished !

jgra1 · Post by **jgra1** » 11 May 2006, 10:20

guys, thanks, I will try again later on.
I like the idea of one wheel on the ground while working on the other..

The car passed its brake test 2 months ago.. but i never carry any weight in it, so that may partly account for the disk condition, also, as said the calipers could be sticky due to no use..

I got some fluid out, when i put a jack under hubs (to try and imitate the car being on the ground) , with suspension on HIGH.

But hopefully the effect should be much stronger with one wheel on the ground (i.e. doing one side at a time)

All I am trying to do is remove any possible air because of these three reasons?

Car dips, rear rises when braking

There is a pulsing at the pedal and an accompanying hiss / squelch noise -
if you keep your foot on the brake hard. (i have changed the Acc sphere)

and probably because of this, the car is hard to stop smoothly.. (the idiot spring is still there, I havent got time to remove it

) but my v6 is mcuh easier to stop and doenst have any of these symptoms...

Car is non ABS by the way

Johnnnnnnnn

AndersDK · Post by **AndersDK** » 12 May 2006, 15:34

John -

First things first :
Find & correct any problems - THEN you go mod the pedal spring - right ?

jgra1 · Post by **jgra1** » 12 May 2006, 16:20

yes

i am not touching the spring..

the car is due for sale right now and i just want to be sure the brakes are all ok and free of air.. the spring can happily transfer to new owner.. I will point it out to them tho

jgra1 · Post by **jgra1** » 17 May 2006, 12:46

sorry for taking time to reply..

well.. I had another go, perfect this time, clear fluid coming from all wheels.. I reckon i got a couple of litres from each corner.. no bubbles..both back brakes were locked on solid

but the car still feels the same

and now it tends stay down at the back.. if you put it on high and then on normal it lowers to correct height, but doesnt come up from down? - i can live with this..

so, the main symptons, :

the brakes still feel odd, the pedal pulses, the brake control valve hisses as it pressurises and depressurises, the front dives a lot, there is a small chance the hydraulic pump may have a leak but I need to confirm this..

Could it be the pump isnt outputting enough, Shall i take it off and renew seals?

Could it be the brake control valve?

there seems to be no air in system,

the accumulator is new

jeremy · Post by **jeremy** » 17 May 2006, 18:36

I know the accumulator is new - but is it working? - Do the sit-in-the-boot test and then you'll know for certain. (Car at normal height with engine running for a couple of minutes. Turn off engine - sit in boot - car should sink a long way, then after about 30 secs rise to its original position - powered by the accumulator. When you get out it should rise again and then sink to its original position if the rear height corrector is working correctly.)

jgra1 · Post by **jgra1** » 17 May 2006, 19:22

yep does this fine J

Gregg1100 · Post by **Gregg1100** » 17 May 2006, 19:46

Hello All,
Can I ask why one would want to return aerated LHM to the tank. You wouldn`t do that with normal hydraulic systems--you wouldn`t get the system bled properly. When I get to have to do my Xantia brake bleed, the old LHM will be discarded. May cost a bit more, but no air or crud left in the system.
Greg

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