Self-levelling Suspension A100 T44

ovalking · 19-06-09, 01:13 PM

My self-levelling rear suspension on 1988 100 Avant has become rather bouncy lately. Even my sister driving behind noticed it.
It seems to have got worse since I changed the hydraulic pump, but that may be coincidence.
Ride height isn't far out, although it does sag when parked.
There are no major leaks from anywhere.
I've not found much information about the system, particularly what faulty parts gives what symptoms.
Does anyone understand how this system is supposed to work? (I understand the basics).

The following thread about a Merc system makes it sound very similar to the Audi one and points to the spheres...
http://www.mbclub.co.uk/forums/wheel...4-spheres.html

I guess the spheres are like the brake bomb, and they lose pressure with age.

Thanks, G.

5potnoodle · 21-06-09, 02:09 AM

BTDT. Presuming that you have used the correct Audi hydraulic fluid (important) and bled the system correctly (also important) after changing the pump then I would think you need your spheres replacing I'm afraid. The suspension will sag when parked for any length of time as the pressure in the system drops so that's quite normal. The spheres contain nitrogen seperated from the hydraulic fluid by a membrane, this acts as the damper in your system. When the membrane leaks the nitrogen, you have no damping and your suspension is bouncing up and down on the springs, just like when a normal shock absorber stops damping. The suspension will still rise and fall because of the hydraulic fluid being pumped into the system.

In theory, it should be possible to recharge the nitrogen spheres with some modification to the sphere itself. I've seen on the web a mod for the brake sphere which involved fitting a car tyre type valve to it so it should be possible for the suspension spheres too I'd have thought. Might be best to go see a friendly Citroen expert to see what they can suggest.

ovalking · 22-06-09, 09:23 PM

Thanks for your notes 5Pot, it's good to have that confirmation.
Correct G002 000 fluid, and bled by steering lock-to-lock method. Everything else seems to be working well, and no leaks from the pump, yippee!
I guess conversion to standard susp. is an option, but the self-levelling system is really good when it works...
So does anyone have any spheres? Good or bad - experimenting with recharging is a possible.
According to Vagcat.com they're 443616203 and 178 Euros each!

Emjay · 22-06-09, 09:31 PM

apologies upfront for going slightly off thread but "sphere replacement" does sound sort of............rude!

then again I am slightly drunk

5potnoodle · 23-06-09, 12:03 AM

Quote:

Originally Posted by ovalking

Thanks for your notes 5Pot, it's good to have that confirmation.
Correct G002 000 fluid, and bled by steering lock-to-lock method. Everything else seems to be working well, and no leaks from the pump, yippee!
I guess conversion to standard susp. is an option, but the self-levelling system is really good when it works...
So does anyone have any spheres? Good or bad - experimenting with recharging is a possible.
According to Vagcat.com they're 443616203 and 178 Euros each!

To be honest, I'm amazed the spheres are still available from VAG. I think new spheres would be cheaper than conversion unless you can do it yourself, especially if you actually like the self-levelling aspect. I know I do

At the very least, you won't need to change them again for another 10 years or so.

The bleed method doesn't sound exactly right to me from what I can remember, though last time I had it done it was about 3 years ago. I know the bleed nipple on the rear suspension hydraulic splitter manifold thingy (where the hydraulic lines all meet up at the rear axle) came into it somewhere.

Incidentally, if you need to you can set the ride height. There's an adjuster on the valve which is connected to the back axle by a rod.

Anyway, let me know how you get on.

ovalking · 20-09-09, 10:10 AM

I finally got round to replacing the suspension accumulators.

Left side was done without issue.

But the right was another story.

Strangely the main connection on this side was a conical seat type rather than the banjo of the left. The nut was too tight for an open-ended spanner and eventually it split into 2.

Then the smaller pipe broke when I undone that.
And then the mounting bolt sheared off, so cut off the welded nut.
Pipes no longer available, so got some made at Pirtek.

Expensive job in the end (accumulators £210 each. Pipes £44. Hydraulic fluid £20) but at least it cured the problem and no more bouncing around!

G.

21-06-09, 02:09 AM	#2
5potnoodle OCD member Classic Audi Club Member Join Date: Apr 2008 Location: Lincolnshire, England. Posts: 196	BTDT. Presuming that you have used the correct Audi hydraulic fluid (important) and bled the system correctly (also important) after changing the pump then I would think you need your spheres replacing I'm afraid. The suspension will sag when parked for any length of time as the pressure in the system drops so that's quite normal. The spheres contain nitrogen seperated from the hydraulic fluid by a membrane, this acts as the damper in your system. When the membrane leaks the nitrogen, you have no damping and your suspension is bouncing up and down on the springs, just like when a normal shock absorber stops damping. The suspension will still rise and fall because of the hydraulic fluid being pumped into the system. In theory, it should be possible to recharge the nitrogen spheres with some modification to the sphere itself. I've seen on the web a mod for the brake sphere which involved fitting a car tyre type valve to it so it should be possible for the suspension spheres too I'd have thought. Might be best to go see a friendly Citroen expert to see what they can suggest. __________________ Current: 99 Subaru Forester S-Turbo Auto - interesting... but it's not a quattro 91 Reliant Scimitar SST 1400 - no.39 of 42... something for the weekend Previous: Two consecutive 1989 Audi 200 Quattro Turbo Avant, 1B 1990 Audi 100 SE Avant, NF 1986 Audi 100 CD Avant, KU 1987 VW Passat GL5E Estate, JS "Honorary" triple member of the 200,000+ Club Audi 200 in the UK (legacy website) Classic Audi member no: 258

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22-06-09, 09:23 PM	#3
ovalking Grown up member Classic Audi Club Member Join Date: May 2009 Location: Ipswich Posts: 270	Thanks for your notes 5Pot, it's good to have that confirmation. Correct G002 000 fluid, and bled by steering lock-to-lock method. Everything else seems to be working well, and no leaks from the pump, yippee! I guess conversion to standard susp. is an option, but the self-levelling system is really good when it works... So does anyone have any spheres? Good or bad - experimenting with recharging is a possible. According to Vagcat.com they're 443616203 and 178 Euros each!

22-06-09, 09:31 PM	#4
Emjay Man Fettler Extraodinaire Classic Audi Club Member Join Date: Jul 2008 Location: Up my own arse blowing smoke Posts: 7,417	apologies upfront for going slightly off thread but "sphere replacement" does sound sort of............rude! then again I am slightly drunk

20-09-09, 10:10 AM	#6
ovalking Grown up member Classic Audi Club Member Join Date: May 2009 Location: Ipswich Posts: 270	I finally got round to replacing the suspension accumulators. Left side was done without issue. But the right was another story. Strangely the main connection on this side was a conical seat type rather than the banjo of the left. The nut was too tight for an open-ended spanner and eventually it split into 2. Then the smaller pipe broke when I undone that. And then the mounting bolt sheared off, so cut off the welded nut. Pipes no longer available, so got some made at Pirtek. Expensive job in the end (accumulators £210 each. Pipes £44. Hydraulic fluid £20) but at least it cured the problem and no more bouncing around! G.