The Occasional Hard Feeling...

[rg]

Folks,

I am getting the occasional "hard" setting on the rear following new
spheres.

I have yet to bleed air via the brake nipples to ensure that the system is
fully bled out.

All four rear spheres were changed, and Citaerobics carried out.

I also have a (maybe irrational) theory that the "mature" accumulator and
middle-aged front centre sphere may have some bearing on the situation - the
4 rears are now brand spanking new, but the front are well due for
replacement.

The problem has only arisen since the sphere change, as far as I can discern
- there was a noticeable difference in ride in turns and on
braking/acceleration with the old spheres.

Plus, it only seems to be affecting the ride at the rear, and only "per
session", i.e., sometimes when I switch on, it's fine, others time not so.

It does not appear to resolve itself in motion.

Any insights welcomed.

Cheers

rg

[jorgy9]

Hi Rob,

I might have a problem similar to yours, in that it occured with sphere changing. From my 2 year-old spheres, I replaced first the 3 front ones with new, and the ride became amazingly good, but then when I replaced the 3 rear ones and accumulator with new, the ride changed again to much worse -different though than when having empty spheres-. In other words, the car was better with the old rear ones!

Noz said he suspects a faulty hydractive electrovalve, but my question is why should this have appear exactly between the car going in to garage for rear spheres change, and going out of it with new rear spheres -only a huge coincidence would explain this-. Plus, the electronics sound as always on the radio.

Because the problem is complex, I thought I'd first establish that my system operates within the right pressure range -145 low to 175 bars high-. The reason is that if the pressures are too low, the hydractive valve(s) can also be caused to close hydraulically -even if the electronics operate correctly-. This is due to the system's design -it's the system's pressure that really keeps the hydractive valve(s) into the position that gives the soft mode.

Anyway, I just thought I'd let you know about those other issues, in case you didn't. In your case however it seems more likely that it's all down to electrics/electronics, only from the fact that, as you say, that the fault goes "per session". It could be also typical of the diode(s) going, or simply a dodgy connection on the way to the rear electrovalve. I also thought that they could have disturbed the electrics at the garage when trying to change the middle sphere, but in my case I can listen on the radio that they operate as always.

regards
George

[rg]

This discovery may have an effect...

http://www.flickr.com/photos/point_and_click/148611729/

How on earth has this happened? I've worked nowhere near it.

I understand that this is the hydractive movement sensor. Would anyone have isolated it for any particular reason?

r

This post has been edited by rg on May 18, 2006 08:53 am

[jorgy9]

Good finding!! Has reconnection cured the situation? How do you explain though your impression of getting the *rear* only in hard mode?
G

[rg]

G.,

Thhe situation has improved slightly, but, yes, it's strange how the rear remains stiff but the front is OK.

It's almost like a valve of some sort is sticking - the times after start-up to the suspension going soft are getting shorter, and there is a definite sensation of the suspension suddenly "softening" as if something has opened which does not relate to any particular movement (braking, steering, accelerating, etc).

Martin at Pleiades suspects that it is not something electrical, but hydraulic.

However, I will get the codes read, and consider refilling with "rinsing agent" fluid.

r

This post has been edited by rg on May 27, 2006 05:43 am

[rg]

An update on this one:-

After 1500 miles on hydraflush, during which time the "hardness" seemed to diminish, I've refilled with LHM, and the problem is back.

The hardness seems particularly noricable after a load has been put in.

There is still the sudden feeling of softtness, akin to a valve opening, after a while.

I'm now suspecting the anti-sink valve.

Can anyone point me in the direction of it, and give any tips on removal and cleaning?

r

[jorgy9]

Hi Rob,

I can help in pointing out how to test that your rear hydractive electrovalve is working properly. I think this scenario should be scrapped first so then u go on to other fields. If it ever stops raining, I'll make a photo of a set up that provides an easy and definitive test of the function of that valve(s).

In the meanwhile, shouldn't the anti-sink valve block the front also (I don't know much of antisinks!) ?

G

[DerekW]

George, no, you have one each for front and rear.

Rob, not sure how the a/s valve could cause your problem. It's designed to be open during normal operation and as it works purely on pressure difference, as long as the main suspension pressure is greater than rear system pressure it must remain open.

If you really want to torture yourself it's tucked up alongside the large tubular suspension cross member just to the right of centre.

It sounds like an electrical problem to me, why don't you do the radio check? Never had to do it myself but I believe you tune the radio to long wave between stations and the electrovalve then produces a buzzing on the radio when it is engaged. That sounds easy enough, you certainly won't get dirt in your eyes the way you will if you start playing about with the a/s valve.

If ther's no buzzing and all electrical connections look sound then it looks like one of Noz's diodes. (Question, do you have a separate diode for front and rear?)

Derek

[rg]

Derek, Jorgy,

Thanks very much.

I've consistenly failed to hear "Radio XM" on any of the frequencies in the past, but will give it another try. The suspension, however, has certainly been is soft mode.

The system is not randomly going into hard at the back, which would point to a de-engergising of the hydractive valve (assuming default being "hard") and a poor connection.

It seems to free off "per session", opening after a period of time, then behaving normally, which tends to point towards something hydraulic suddenly freeing off, and staying free.

Then switiching off, and switching on again, particularly with added load, it goes hard again, and frees off with a "whoosh" feeling, lowering the back end very slightly, sometimes at standstill, but always, then, giving a softer ride.

Running with Hydraflush certainly gave an improvement. Maybe some debris in a valve? I had a couple of pipes rot through in recent time, although the escaping fluid should have pushed any debris away, not drawn it into the system, I guess.

r

[jorgy9]

It definitely sounds like the rear hydraulic valve is opening/closing for some reason -and the tendency to clse when u load (if ur observation is right) just shows a weakness in the pressure pushing it open. I'm having similar symptoms, and I suspect it's a sticky hydraulic valve, or lack of pressure to keep it open, somewhere. Why, don't ask me, it could be down to

1/ leaky hydractive valve on the return outlet (the electrically controled one)
2/ a blockage on the high pressure pipe
3/ a mechanically worn/sticky hydraulic valve.

By coincidence, on Wednesday I'm booked on a ramp to perform the various pressure measurements that will reveal the cause. Last week I spent at least 1 day per hydractive valve driving around as usual but with a voltmeter plugged in to check for correct electric+electronic function -just not to waist my time with more difficult tests-. The "radio-XM", I can perfectly hear, it but I wouldn't suggest it to somebody that has never heard it as a means of diagnosis in case something is suspected to be wrong.

As said, I'll post a description of what to do and then u see how u continue.

regards
George

[rg]

Jorgy9,

Thanks very much

>or lack of pressure to keep it open, somewhere. Why, don't ask me, it could be down to ...

The pump seems pretty healthy, with the car rising promptly in the morning.

Low to high during "Citaerobics" takes around a minute or so. I have nothing like the probelsm with rising as described by other members.

It does, indeed, sound like a blocked or sticking valve, which would explain why it ran a bit better with Hydraflush, I guess, and that it only seems to affect the rear ride.

What frequency are you using for "Radio XM"?

r

[DerekW]

Rob,

I wondered whether your rear a/s valve might be sticking closed, I've never heard of this happening but it would prevent supply pressure from operating the hydraulic selector valve. I'm sure you've already thought of this and that's why you were querying its location.

Fortunately there is an easy check. After you've finished driving for the day select "low" on your suspension and wait for it to settle completely before you switch off the engine.
Leave it overnight for the accumulator to empty (alternatively depressurise it). Immediately before you start the car again, select the normal ride height. At this stage the rear suspension will be empty of pressure and there will be no supply pressure so the a/s valve will be in equilibrium but closed by its return spring. Now start the engine. Both a/s valves should open almost immediately as the supply pressure builds up and the back end should rise first because of its lighter loading. If it doesn't, your rear a/s valve is stuck closed.

Derek

[rg]

DerekW,

Thanks for your concern and response.

Yes, it feels like a valve opening and allowing LHM to pass. Don't ask me why, just a (literally) "seat of the pants" thing! Iy only started after I renewed all my spheres, including the anti-sink.

I'll try it if I ever get the car back off my wife...

Thanks again.

rg

[DerekW]

These cars of ours are always finding new ways to bite our backsides. Please keep us posted on your progress.

Derek

[rg]

I took plenty of photos when I changed the anti-sink sphere (and others)

Is this the valve here? Run your cursor over the image to read the note.

http://www.flickr.com/photos/point_and_click/303497019/

Cheers

rg

This post has been edited by rg on November 22, 2006 04:19 pm