Unexpected results from changing front spheres.

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isisalar
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Unexpected results from changing front spheres.

Post by isisalar »

I'm working my way through the hydraulics on the HDI exclusive I bought back in December, the rear spheres having been recently replaced, according to the service history.
I've had hydraflush in for about 600 miles now and have replaced all the front 4 spheres, only the rear accumulator and anti sink to go. Need to get the brakes bled PDQ to get some hydraflush through but my local garage is a bit frightened of it I think and I don't have the necessary stands etc.
Changed the original? Citroen 3 dot front spheres last week, in record time, for 2 new GSF sphere's. Filling date 2010 IIRC.
Has improved the ride as expected.However, when performing citrobics the front end now rises and falls in a series of 'pulses'. It most definitely did not do this previously and it's noticeable when the height adjusts itself in normal driving, whilst parking, at lights etc.
Thinking back, my previous VSX did this too and that also had GSF spheres fitted although it wasn't as obvious when driving.
I'm kicking myself now for throwing the originals away, I could probably have got them re gassed.
The car seems to be sinking more overnight the longer the hydraflush is in.
What's puzzling me is what's the problem? Could the wrong spec sphere cause this or now the pressures correct is it indicating another problem?
Another unexpected result of fitting them has been the unwelcome appearance of some really annoying noises from the front suspension, but I guess that's the drop links, now there's some pressure in the spheres it's showing up?
A local indy did a simple test for a faulty drop link for me once I think involving bouncing the front end whilst manhandling a wheel but I can't remember now. Can anyone oblige please?
Very close now to experiencing Hydractive with all good spheres at last, now just need to get the injectors and the whistling sorted out, but that's another thread, and the droplinks, and the p bushes, it never stops does it?
Kind regards
Paul

addo
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Post by addo »

Easiest test for the droplinks is with both front wheels clear of the ground - twist/wiggle each end of each link - there should still be a firm tightness to each ball/socket.

I'd say the pulsing movement is more likely issues with the height correction linkage; a coincidence or possibly affected by a different rate of fluid flow (if the originals were ruptured the flow would have been less).

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Xaccers
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Re: Unexpected results from changing front spheres.

Post by Xaccers »

Jerky rising and lowering at the front?
Pull down the gators and lube the struts.

isisalar
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Re: Unexpected results from changing front spheres.

Post by isisalar »

The front and rear heights were recently set by BL auto's so I don't think it could be the correctors and the pulsing is too regular and occured so suddenly after changing the spheres to be friction induced.
I'll check but I think it's 7 stages up and down regular as clockwork and smooth as silk, no jerks.
Could this possibly be a wrong spec. sphere setting up some sort of 'wave' effect? IIRC the GSF accumulator spheres ,which have been fitted are slightly higher pressure and capacity than spec. could this be a factor?
Off now to get some cleaner through my injectors.
Thanks Xac and Addo
Cheers
Paul

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xantia_v6
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Re: Unexpected results from changing front spheres.

Post by xantia_v6 »

The dropping in steps is due to friction, probably in the front struts, and is quite common. You new spheres may (should) have a lower spring-rate, compared to the friction, causing the oscillation. I would not worry about it, but if you are worried, try lubricating the struts.

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Mandrake
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Re: Unexpected results from changing front spheres.

Post by Mandrake »

isisalar wrote: I've had hydraflush in for about 600 miles now and have replaced all the front 4 spheres, only the rear accumulator and anti sink to go. Need to get the brakes bled PDQ to get some hydraflush through but my local garage is a bit frightened of it I think and I don't have the necessary stands etc.
You don't need stands to bleed the brakes, in fact they just make the job more difficult as the car is too high off the ground then for a jack.

All you need is a jack that will let you remove one wheel at a time. The wheel change jack at a pinch, but I prefer to use a trolley jack. See my bleeding method near the bottom of the following page:

http://www.frenchcarforum.co.uk/forum/v ... 8&start=15" onclick="window.open(this.href);return false;

This is for the rear suspension but its much the same for the front, just skip step 5 for the front.

isisalar
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Re: Unexpected results from changing front spheres.

Post by isisalar »

Got a local tyre place to bleed the brakes under my instruction last weekend(for £20), as described in mandrakes post, thanks Simon,
suprisingly improved the ride and also threw up another conundrum I'll ask about later.
Still feeling that the low speed ride should be better doing a bit of wing pushing I discovered that there is quite a bit of stiction on the front. So, thanks to xac and v6's advice I'm going to lubricate the front struts.
Not suprisingly googling the subject mostly threw up posts on this forum but not a definitive answer to the question of what to use.
Oil, grease, lithium grease, and LHM have all been recommended, my first thought was to use spray silicone grease but I thought I should check with with all you experts if this would do any harm or good?
From what I remember when I changed the strut tops the gaitors pull off and are a pain to put back on, IIRC a large screwdriver was needed to push them back on?
The hydraflush that's in it felt a lot thinner and less slippery than LHM and I think it may have been very old and possibly degraded? The previous time I did a flush it felt almost identical to LHM. Does the LHM provide lubrication for the strut?
It does appear that any surface lubrication would be scraped off as the strut goes up into the top or are we talking microscopic amounts , the reason I thought of the silicone grease.
I'll post up the other mystery later.
Kind regards
Paul
Paul

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Re: Unexpected results from changing front spheres.

Post by Old-Guy »

Lubricate the front struts with LHM, which is what the seals are designed to keep in and therefore can't hurt them. LHM, unlike other hydraulic fluids, is mineral based thus not hygroscopic (doesn't absorb water-vapour from the atmosphere).

The secret to replacing strut boots is to wipe the retaining lip thoroughly clean, and to start from the inside (nearest the inner wing), working evenly round both 'sides' towards you. If you use any tools, you are likely to damage the boot. It's easier when the weather is warm and/or the boot is new as the plastic is softer, but I've done it with an old boot in a really cold workshop.

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Mandrake
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Re: Unexpected results from changing front spheres.

Post by Mandrake »

The problem with LHM is its a very thin oil, not very clingy and not designed as a lubricant so it won't stay there for long...which is why I use mineral based lithium grease. It's compatible with the seals and clings around the top bush area much longer, staying effective for up to 6 months or so, compared to LHM which might stay there for a few weeks at best before losing effectiveness.

I don't know if other people do this but I use multiple applications as well - suspension right up (axle stands for safety before putting fingers into the gap!) apply grease to the shaft, lower the suspension down, lift it up again and repeat twice more. This helps work more grease into the cavity inside the strut below the top bronze bush making it more long lasting.

You're right about the boot lip - it has to be oil/grease free before refitting, I try my best not to get any grease or oil on either the top of the boot of the lip on the strut top...if I do I wipe it throughly clean. There's a couple of different kinds of boots - the old ones are quite short (they only just reach when the suspension is on high) and are made of a fairly hard plastic like material. These ones you can sort of grasp them with your hand and wriggle them on, rotating them to help them go on.

The newer type of boot is a much softer rubber like material and also is much longer with more ripples. On these ones I find it easiest to just push my thumbs up through the boot around the back to slip the back edge over the lip and then work my way around, then grip the lip with one hand and pull the boot down to straighten out the ripples, then rotate the boot to make sure its on the lip properly.

One final comment about lubricating the struts in general, there is a bit of a placebo effect... :lol: By that I don't mean its all in your head, however I mean that the lubrication isn't the only explanation of the sometimes temporary improvement in ride after strut lubrication.

In the process of doing the job you are effectively doing citrorobics, especially if you raise and lower the suspension multiple times as I do. That alone is enough to give a temporary ride improvement as it flushes out any accumulated air/nitrogen in the suspension, as well as working the suspension mechanically through its full range of motion.

To prove this theory I once went through the motions of lubricating the struts and followed my normal procedure apart from not applying any grease! :twisted: Surprisingly the ride improvement was almost as good as it is with grease/oil...

Although lubricating the top bush does definitely help, especially if the struts are actually jumping or creaking, the top bush if you look at the design of the strut in detail is actually designed to run without lubrication, as there is not even a leakage path to lubricate it. A design flaw in my opinion, I toyed with a number of ways of keeping it more permanently lubricated (including a felt washer hugging the shaft glued to the top of the strut as a LHM reservoir that would keep the shaft wetted just above the top bush) but decided it was more hassle than it was worth...
Last edited by Mandrake on 09 Jun 2013, 21:25, edited 1 time in total.

isisalar
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Re: Unexpected results from changing front spheres.

Post by isisalar »

Prior to getting down and dirty with the struts I've been doing some more investigation and observation to try and cure what is a very poor low speed ride.
After the improvement in ride after bleeding the brakes and it's deterioration since, and thanks to an earlier post from Mandrake, I think that the improvement may be due to the car ticking over on high for about an hour while the brakes were bled, purging out all the air/nitrogen in the system.
Similar process has repeated the improvement. Testing the front end immediately after lowering and it's perfect and floaty, after a 8 mile journey in traffic, when testing again, the front end seemed to be rock hard initially but after pushing fairly hard becomes soft and floaty again.
I'm hoping and praying that this is wholly due to nitrogen coming from either the anti sink or the rear accumulator sphere and I'm picking up new ones this afternoon but there are a few other things that may be relevant.
At very slow speed when applying the brakes there seems to be a millisecond delay between the pedal and the pads, at anything over walking pace they're fine. Bleeding has improved this but not cured it.
When turning on the ignition there is a distinct thump from the rear of the car. Being my first HDI I assumed this was the fuel pump reaching pressure but during a lexia session with Dickie G he said he'd not heard it before but it wasn't the fuel pump. This noise has similarly diminished by about 50% after the brake bleeding I think. I noticed yesterday that the hydractive light is coming on momentarily when starting and is connected to the noise. I don't know if this is normal or does this point to some sinister hydractive problem with electrovalves.
Also on start up which may or may not be relevant, since a few months ago the red stop light with the temp guage red light stay on when ticking over, goes out with the first touch of throttle.
Hopefully get the new spheres on this weekend, and then get the flush out and LHM in in a few weeks.
I really hope I haven't got any air leaks.
Cheers everyone
Paul

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Mandrake
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Re: Unexpected results from changing front spheres.

Post by Mandrake »

Hi Paul,

There is another possibility for intermittently harsh ride with Hydractive 2 that I had forgotten about, but was reminded of a few days ago - sticking slide valve in the hydractive control block itself.

The switching from hard to soft and back actually involves two things - the electrovalve, which is screwed onto the side of the hydractive block, and the main slide/shuttle valve deep down inside the hydractive control block. (Refer to the hydractive 2 training manual for pictorial diagrams)

The electrovalve is a simple hydraulic changeover switch which controls pressure on a control line that operates the slide valve. Power applied to the electrovalve provides full hydraulic pressure to the slide valve pushing it in, no power applied causes the electrovalve to provide no pressure to the control block, allowing it to return. The slide valve is what actually connects and disconnects the hydractive regulator sphere.

However even if the electrovalve is working perfectly if the slide valve doesn't move the suspension can stick in soft or hard mode. As hard mode is the "default" mode it seems to be that when it misbehaves it sticks in hard mode.

An example of this is some cars (mine used to do this but stopped for some reason) when being started and lifting up in the morning will lift up to the correct height at both ends, then if you stay put some random amount of time between a few seconds and 60 seconds or so there will be a slight thud and the rear suspension will drop a couple of inches, then correct itself again...

This I believe is the rear hydractive slide valve staying stuck in the hard mode despite the electrovalve being energised. The thud is when it finally switches over allowing the pressure to the 3rd sphere which was previously cut off to equalise. For whatever reason this seems to happen more with rear suspension than front - both my Xantia's have intermittently had this behaviour at the rear despite replacing the electrovalve on the first Xantia...

I'm not sure why the slide valves seem to get sticky, I speculate that the o-rings on them eventually deteriorate and get munched up by the valve getting wedged in the valve in inopportune locations such as to intermittently prevent the valve from sliding fully from end to end. Most likely stripping the valve block down and renewing the o-rings would cure this problem once and for all, but I don't know of anyone who has been brave enough to strip one right down and overhaul it!

One thing that seems to help free up the slide valve a bit though is this:

Lift the suspension right up, let it idle 2-3 minutes then turn the engine off. Wait one minute until the electrovalves have closed. Do not open any doors. Put the height lever back to the middle, the car should go down to the normal height. After it has gone down start the engine and in a few seconds both ends of the car should jump suddenly up like a cork being released under water. :)

What's happening here is we have put full pressure into the suspension, lowered the suspension while the 3rd sphere is isolated so that there is a large pressure difference between them, starting the engine then turns the electrovalves on and causes the pressure to equalise. The violent jump in height seems to exercise the slide valve in such a way that it frees it up a bit.

I accidentally did something similar yesterday after working on the car - the suspension had been up for a few minutes, I lowered it down without starting the engine, later when I started it it popped up like a cork, when I drove off down the road I noticed that the ride was extremely good and more importantly consistent for the entire duration of the trip - normally it intermittently feels like one end of the car is stuck in hard mode...

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Re: Unexpected results from changing front spheres.

Post by isisalar »

Thanks Simon I'll give that a try shortly, my old VSX used to do those jumps during citrobics. Could be the start of a new art form, Xantia dancing?
Incidentally the 'pulsing' was far less evident when lowering the car after ticking over on high for 20mins.
Cheers
Paul

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Re: Unexpected results from changing front spheres.

Post by myglaren »

Mandrake wrote:
I'm not sure why the slide valves seem to get sticky, I speculate that the o-rings on them eventually deteriorate and get munched up by the valve getting wedged in the valve in inopportune locations such as to intermittently prevent the valve from sliding fully from end to end. Most likely stripping the valve block down and renewing the o-rings would cure this problem once and for all, but I don't know of anyone who has been brave enough to strip one right down and overhaul it!
I have a vague recollection that Jim did just this a couple or three years ago. Hopefully he can confirm and link to his run through.

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Mandrake
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Re: Unexpected results from changing front spheres.

Post by Mandrake »

I've had the Hydractive control blocks partially stripped down before - with both large side plugs removed where the large diameter pipes go in, and the damping valves removed, that much is easy, however I haven't taken out the shuttle valve, and that's where the problem, if it exists, will be.

I'm reasonably sure a malfunctioning shuttle valve is what causes intermitent harsh ride on Hydractive 2's where all other things have been ruled out including electrovalves. What exactly causes it not to switch I can only speculate though.

isisalar
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Re: Unexpected results from changing front spheres.

Post by isisalar »

I've just done the jump procedure but it only jumped at the front and without the engine even starting, from the accumulator I suppose. Off to get the spheres now so we'll see what happens when they're fitted.
Could be the rear accumulator is so flat it can't operate the valve?
Cheers
Paul