Hi all,
Long story, but read it please and help if you can [:)]
I have struggeled with my 2.0i '90 XM suspension now for a year already and still no result. Problem is that suspension is fine and smooth on the road bumps, but in lower speed (in city traffic) it senses quite hardly most of the pot-holes. Seems like suspension reaction time has longered - not reacting enough fast to road changes. Electrically everything is fine, HC-s are cleared, new spheres all around, brake valve is just changed, LHM is changed and is clear, PR is clicking after every 40 sec approx. But still I'm not happy with suspension. I have started to think that maybe my hissing FDV is somehow involved to suspension hardness, because it can limit lhm flow and is last device I haven't changed [:p]. When car is on idle, there is almost no LHM flow and car is bouncy all around, but I think that while driving in lower speed, there is not enough lhm flow, to open centre spheres...
So the question follows, can FDV ruin suspension comfort? Have anyone get his flying carpet suspension back after FDV change?
One more thing, once I had to open FDV cause some piece of rubber obstructed one orifice what limited steering power. After clearing, putting new filters and sealings on, my car's steering and even suspension and brakes improved a lot. I was surprised. Also car stood up 2-3 days. But it last only a week. Then I took FDV off once again, found actually nothing, put together and the anomaly recured! But not anymore nowadays...
Regards,
Priit
Can FDV ruin suspension comfort?
Moderator: RichardW
Hi Priit -
The FDV has nothing to do whatsoever with the suspension.
All it does is to prioritise the feed pressure from pump to servo and PR.
As your PR emits a tick every 40sec's it is fed with adquate pressure, which would be missing with a failing FDV leaking the pump pressure feed.
It's the 40sec's PR tick interval you should pursue. It's a bit too lowish to be perfect, and indicates you may have a weak main accumulator sphere.
Try it out :
Have engine idle, car parked. Deliberately set the suspension to lowest height, wait untill you reckon the suspension settles on the rubber stops. Now time the tick interval from the PR. It should be at least 1.5 - 2 minutes.
Note that it's pure lotteri to buy s/h or recon spheres for the main accumulator, as this sphere is constantly charged to the max system pressure of approx 170bar, and therefore constantly is exposed to more working stress than the suspension spheres.
The FDV has nothing to do whatsoever with the suspension.
All it does is to prioritise the feed pressure from pump to servo and PR.
As your PR emits a tick every 40sec's it is fed with adquate pressure, which would be missing with a failing FDV leaking the pump pressure feed.
It's the 40sec's PR tick interval you should pursue. It's a bit too lowish to be perfect, and indicates you may have a weak main accumulator sphere.
Try it out :
Have engine idle, car parked. Deliberately set the suspension to lowest height, wait untill you reckon the suspension settles on the rubber stops. Now time the tick interval from the PR. It should be at least 1.5 - 2 minutes.
Note that it's pure lotteri to buy s/h or recon spheres for the main accumulator, as this sphere is constantly charged to the max system pressure of approx 170bar, and therefore constantly is exposed to more working stress than the suspension spheres.
1.5 - 2 minutes! On an XM - you've got to be joking! Anything over 30 seconds is good and on a 1990 car , 40 secs is a miracle. No, I don't think its the accumulator. I'd be more inclined to start looking at the hydractive components - it's a fair bet the car is going straight into sport mode as soon as it starts moving-.
//NiSk
//NiSk
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tomsheppard
- Posts: 1801
- Joined: 19 Dec 2002, 14:46
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More information 
Electrically everything is OK, I can feel difference between AUTO and SPORT, but still AUTO is too hard. Have driven voltmeter connected to el.valve - ECU is not switched/locked itself to hard, it reacts to all 5 sensors as it should. Spheres are bought 5 moth ago from local Citroen dealer and are original so. I also measured those before put them on. Rear arm bearings are changed. I have took off height-correctors and cleaned those. I have even took off stiffness regulators! Nothing. Ahh, front is lazy to rise. It take a lot more time to rise when I sat on the bonnet comparing to rear.
But how the suspension can be soft in high speed and not in lower speed when el.valve is opened? I remember, when bought my XM, I drove almost all the time switch in SPORT mode and car was still soft...AUTO was like too soft for me.
But what if there is still not enough lhm flow (limited by FDV) to suspension, to oped stiffnes regulator? Sometimes I hear also faster, after 5 sec or so PR clicking in city traffic, but mainly not so fast. I know what would help - to measure hydraulic pressure while driving, but unfortunately I can't do that...
Regards,
Priit
Electrically everything is OK, I can feel difference between AUTO and SPORT, but still AUTO is too hard. Have driven voltmeter connected to el.valve - ECU is not switched/locked itself to hard, it reacts to all 5 sensors as it should. Spheres are bought 5 moth ago from local Citroen dealer and are original so. I also measured those before put them on. Rear arm bearings are changed. I have took off height-correctors and cleaned those. I have even took off stiffness regulators! Nothing. Ahh, front is lazy to rise. It take a lot more time to rise when I sat on the bonnet comparing to rear.
But how the suspension can be soft in high speed and not in lower speed when el.valve is opened? I remember, when bought my XM, I drove almost all the time switch in SPORT mode and car was still soft...AUTO was like too soft for me.
But what if there is still not enough lhm flow (limited by FDV) to suspension, to oped stiffnes regulator? Sometimes I hear also faster, after 5 sec or so PR clicking in city traffic, but mainly not so fast. I know what would help - to measure hydraulic pressure while driving, but unfortunately I can't do that...
Regards,
Priit
Just did the test as AndersDK suggested. In normal height PR clicking after 35 sec. In lowest height almost the same, a bit more, 35-40 seconds. And in heighest height only 15 seconds! Very interesting. And during that test I heard 3 times "sssssshhhhh" sound from front HC after what front shaked up and down a bit, and then settled down to normal/set height.
Regards,
Priit
Regards,
Priit