There have been alot of post recently regarding changing suspension spheres and I am now going to do the job on my 1998 Xantia 1.9TD Estate.
One question that has not been asked is:
Do I need to bleed the brakes after replacing the spheres? As they use the same system as the spheres will air not get into the system when the spheres are removed?
Thanks
Richard
Sphere Change
-
Dave Burns
- Posts: 1915
- Joined: 14 May 2001, 05:30
- x 2
Its true that a small amount of air does get in when the rear sphere's are replaced.
This can only find its way into the rear brake circuit if the suspension isn't cycled a few times between maximum and minimum, any air that has got in is then expelled from the suspension cylinder's, through the height corrector and down the operational return pipe to the reservoir, at which point it rejoins the atmosphere with no harm done.
Do not however operate the foot brake during this excercise, this will cause fluid to move along the rear brake pressure feed pipe to the brake valve, possibly taking air with it.
The front suspension has no connection with the front brakes, any air getting in here is of no concern to the front brakes, though any that does get in will again be removed during the Citaerobics.
Air can only get to the front brakes when the accumulator sphere is removed for changeing or the LHM is allowed to drop to an extremely low level, to a point where it is drawn in by the pump.
Dave
This can only find its way into the rear brake circuit if the suspension isn't cycled a few times between maximum and minimum, any air that has got in is then expelled from the suspension cylinder's, through the height corrector and down the operational return pipe to the reservoir, at which point it rejoins the atmosphere with no harm done.
Do not however operate the foot brake during this excercise, this will cause fluid to move along the rear brake pressure feed pipe to the brake valve, possibly taking air with it.
The front suspension has no connection with the front brakes, any air getting in here is of no concern to the front brakes, though any that does get in will again be removed during the Citaerobics.
Air can only get to the front brakes when the accumulator sphere is removed for changeing or the LHM is allowed to drop to an extremely low level, to a point where it is drawn in by the pump.
Dave
-
RichG
- Posts: 173
- Joined: 27 Oct 2002, 01:36
-
Dave Burns
- Posts: 1915
- Joined: 14 May 2001, 05:30
- x 2
No, the front brakes wont require bleeding either if you play your cards right.
Screw on the new accumulator sphere, leave the pressure release screw on the regulator open, one turn is sufficient (don't remove it completely), height lever at minimum, start the engine and let it tickover for a minute, this circulates LHM through the regulator return, taking with it any air that has entered the pipework at the regulator.
With the engine still running, height still at minimum, close the release screw for about five seconds and then open it again, do this three or four times. it will flush out into the return any air that gets trapped in the neck of the sphere when it is screwed on.
By doing this you will have prevented most of the air that gets in from entering the high pressure feed to the rest of the car, but just incase some has got passed these precautions, engine running, height still at minimum, close release screw for the last time and allow the sphere to reach maximum pressure, this is when the regulator cuts out with the characteristic click, not when the pressure warning light goes out on the dash.
Then move the height lever to maximum, this will drain the pressure from the accumulator into the suspension very quickly, blasting any remaining air along with it, as it goes through the security valve it will not be able to enter the feed where the front brakes branch off, because this is allready at pressure, it will simply go straight through into the suspension where it can be expelled during a few suspension cycles, if indeed any has got this far at all.
Do not operate the foot brake during any of these excercises.
The pressure warning light will glow for a few seconds when going form minimum to maximum suspension settings and is normal, when at minimum, pause for a few seconds before raising the car again to allow the sphere's to fully discharge each time.
If you really want to bleed the brakes, this operation should be made to coincide with a complete fluid change, so have a look at the colour of the LHM in the tank, green is good, brown is bad, it should stay in no longer that 36000 miles or three years, which ever comes first.
Dave
Screw on the new accumulator sphere, leave the pressure release screw on the regulator open, one turn is sufficient (don't remove it completely), height lever at minimum, start the engine and let it tickover for a minute, this circulates LHM through the regulator return, taking with it any air that has entered the pipework at the regulator.
With the engine still running, height still at minimum, close the release screw for about five seconds and then open it again, do this three or four times. it will flush out into the return any air that gets trapped in the neck of the sphere when it is screwed on.
By doing this you will have prevented most of the air that gets in from entering the high pressure feed to the rest of the car, but just incase some has got passed these precautions, engine running, height still at minimum, close release screw for the last time and allow the sphere to reach maximum pressure, this is when the regulator cuts out with the characteristic click, not when the pressure warning light goes out on the dash.
Then move the height lever to maximum, this will drain the pressure from the accumulator into the suspension very quickly, blasting any remaining air along with it, as it goes through the security valve it will not be able to enter the feed where the front brakes branch off, because this is allready at pressure, it will simply go straight through into the suspension where it can be expelled during a few suspension cycles, if indeed any has got this far at all.
Do not operate the foot brake during any of these excercises.
The pressure warning light will glow for a few seconds when going form minimum to maximum suspension settings and is normal, when at minimum, pause for a few seconds before raising the car again to allow the sphere's to fully discharge each time.
If you really want to bleed the brakes, this operation should be made to coincide with a complete fluid change, so have a look at the colour of the LHM in the tank, green is good, brown is bad, it should stay in no longer that 36000 miles or three years, which ever comes first.
Dave
-
RichG
- Posts: 173
- Joined: 27 Oct 2002, 01:36