Suspension Problem - Peugeot 405 GRx4

The rear suspension has become very soft on my 1993 405 GR 4x4.

By "soft" it behaves as expected when stationary, but when moving the
rear end bounces far more than normal.

To complicate matters, I have been led to believe that the rear axle may
be a Citroen unit on this model of car.

Is it possible that one of the units is leaking? (I have recently had to
add fluid to the resevoir and the level is now correct) If so, can air
get into the unit and cause this effect?

Are there bleed valves?

All suggestions appreciated. I have also cross posted this to the
Citroen group in case it is a Citroen rear axle.

Cheers

Peter

 

Hi Peter! (Sorry for my bad English)

I believe your problem is the accumulator. This should be a green
"metallball"
mounted under the back of your car. This is a part that is very easy to
replace.
It's like changing a normal light bulb. But it may be hard to get it loose
in some cases.
Now your car is very soft in the back. That's because the green ball is
usually filled whith
some sort of gas and is held in place by a membrane. When the membrane leaks
the gas flows out to the hydraulic fluid and the car gets soft.
After a while the gas will leak out to free air and the car will become
very hard instead as there is nothing to compress.

Those green metallballs are also used in Citroens with hydropneumatic
suspension.

Hope this will help!

Cheers Thomas.

 

case it looks pretty well plumbed into the hydraulic system. Do I
assume I need to remove all the pipes and electrical connections to
replace the "sphere"?

(I assumed from other posts that it just screwed in somewhere, but there
is no sign of it on this car). Have a look at:

www.wsheppard.pwp.blueyonder.co.uk/pug/pug_sphere_1.jpg
www.wsheppard.pwp.blueyonder.co.uk/pug/pug_sphere_2.jpg
www.wsheppard.pwp.blueyonder.co.uk/pug/pug_sphere_3.jpg
www.wsheppard.pwp.blueyonder.co.uk/pug/pug_sphere_4.jpg

I reckon that this is the accumulator. So, do I have to remove all the
connections to do the change? How much fluid will I lose?

Cheers

Peter

 

Hi!

That's the one yes! You don't need to remove anything but the "sphere".
Just screw it out as it has threads(?) just like a light bulb.
I changed my once on my old car (Mi16x4).
It was really hard stuck, so I had to use a very big tool (tongs?).
Just screw the same way as a light bulb.

You will not loose much fluid. I didn't. I think I lowered the car
to minimum level before I started so there would be no preassure
in the system.

If you don't know how to do it I will explain it for you:
On the drivers side of the car in the boot (trunk) you will find
a switch knob and a plug. The knob is to rise the suspension to
the highest level. When you press it again it will wait a few seconds
and go back to normal. The plug has to connections. Just take a
screwdriver or somethind metal and shortcircuit these two connections.
The car will sink down to minimum.

I hope this helped you. It is a very quick way of changing the "springs"
on a car! (If it is not very stuck)

Cheers.

Thomas.

 

I believe your problem is the accumulator. This should be a green
In Citroen parlance, they are spheres, and unscrew like oil filters - if you
do it yourself you will probably need a strap or chain wrench like you use
on a oil filter.

Have a chat with a back-street citroen specialist - they'll tell you 'how to
do it' for sure.

Adam H

 

Hi,

All info in these posts is OK - strap wrench, release pressure
beforehand etc, just like a hydropneumatic Citroen. I'd like to add:

- the release torque on the sphere will be around 40 lbs-ft-f - not very
tight, but enough to call for a 1' lever for comfort;

- Citroen spheres are gas springs, filled with nitrogen at around 70-75 bar
pressure. They lose 5-7 bar per year due to 'porosity' effects (molecular
interstitial losses across the membrane), and need to be recharged every 4
years or so in order to keep the system they're fitted to in proper working
order. If they lose sufficient pressure (due to neglect), the internal
diaphragm gets punctured and the sphere is then a write-off (and would have
to be replaced rather than refilled);

- you should check the level of the (presumably green LHM) suspension fluid
before you start work on the sphere: because if the sphere's diaphragm is
punctured, a certain amount of fluid will have migrated into the space
previously occupied by the inert gas filler and will be lost when you
unscrew the sphere from the axle housing;

- if there are other spheres on the axle (I don't know the GRx4, but there
may be) bear in mind that they'll be in the same state as the accumulator
sphere and will also need to be replaced;

- after seeing your website photos, I'd suggest most strongly that you
consider replacing the hydraulic pipes as well as the sphere, as soon as you
can, using cupro-nickel or Kunifer piping. I've found that this material
works very well on Citroen suspension repairs because it's malleable and
corrosion-resistant;

- if your brake pipes are in a similar state to the hydraulic pipes, I'd get
those changed at the same time (using the same material - cupro-nickel). I
realise that the cost of doing this work might actually be uneconomic,
considering the age of the car - but it might be a lot cheaper than a sudden
and unexpected MOT failure. If you feel inclined to keep your costs down by
trying to do the work yourself, I can say that the only specialised tools
you'll require will be a Sykes-Pickavant Flaring tool (or similar), with a
supplementary die set that's been made especially for flaring the
smaller-bore Citroen hydraulic piping (see below) - and a decent bench vice
to hold it steady;

- if you need to buy replacement spheres, cupro-nickel piping (and the
special pipe-flaring die set), and replacement hydraulic unions and rubber
seals, one company that would probably help you is
http://www.pleiades.uk.com/. I've had good dealings with them on all
occasions in the past, and would deal with them again anytime;

- the hydraulic suspension system on hydro Citroens is self-bleeding: you
simply exercise it a few times to flush any trapped air back into the fluid
reservoir (where it can escape), and that's it. However, the rear brake
hydraulic circuit is usually supplied from the rear suspension hydraulic
circuit (via the brake-pedal demand-valve), in order to make sure that rear
brake power is regulated in direct proportion to rear-axle load. As a
result, air (or gas) introduced to the suspension circuit can find its way
into the rear brakes, and defeat how they should work - so it's necessary
to bleed those items separately in order to make sure that all air has been
eliminated. If *your* rear axle system is set up like this, you need to bear
this in mind as well. Personally, I'd get the manual and see what's in store
before making any decisions.

Good luck.

Regards,

Philip Andrews