c5 suspension pump refit

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sportingfiat
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c5 suspension pump refit

Post by sportingfiat » 19 May 2009, 22:09

new suspension pumps come today been trying to check up when i fit it, is it easy to bleed the system

cachaciero
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Re: c5 suspension pump refit

Post by cachaciero » 19 May 2009, 23:20

sportingfiat wrote:new suspension pumps come today been trying to check up when i fit it, is it easy to bleed the system
In a word No! not unless you have a Lexia.

Just been through this exercise as part of an ongoing effort to try and improve the suspension.

The following is essentially the way that Citroen say to do it in their service docs. Basically this is what you do.

Put suspension to low setting ensure LDS fluid level is to at least the lower level of filler.

Using the Lexia depressurise the suspension, this ensures that the suspension cylinders really are at the end of their travel.

Now you need to apply 0.5 bar that's about 7 psi in old money to the resevoir i.e pressurise it.

Now start the engine and cycle the suspension several times through it's max high to low settings while at the same time exercise the steering lock to lock a few times.

Finish exercise remove pressure source.

Now the question will be can any of this be got around without the special tools and what happens if I don't do it this way.

I believe that the use of a Lexia to depressurize the suspension is essential, while there are mechanical pressurization bleed screws that will release the pressure they will at the same time admit air which kind of defeats the object of the exercise.

I am not sure of what the object of pressurising the resevoir for bleeding is except that it will positively force the air into the pumps.

I havn't yet worked out an easy way of pressurizing the resevoir so I did the following.

Citroen say that the oil level in the tank is checked and topped up with the suspension in LOW. I decided that if I filled the tank virtualy to the filler cap at NORMAL then when the suspension was cycled through to low there should be some positive pressure in the system as the only place for the extra oil to go was into the tank. I just worked on the basis that all the plastic and rubber bits would stretch a bit ;-) Anyway seemed to work although it might be a good idea to take some out now I've finished the exercise.

Caution if you do this DO NOT release the filler cap with the suspension in LOW.

If you don't do it the Citroen way and just put oil in and cycle the suspension and steering then you will probably get most of the air out of the steering but some will likely be trapped in the suspension and it will affect suspension performance you may end up with a suspension that feels very lumpy and harsh although it will be good enough to get you to somewhere that can do the job right.

Cachaciero

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Re: c5 suspension pump refit

Post by wheeler » 20 May 2009, 01:10

cachaciero wrote:
sportingfiat wrote: I havn't yet worked out an easy way of pressurizing the resevoir so I did the following.
A normal cooling system pressure testing kit with various cap adaptors does the job perfect.

I dont see why the system needs to be de pressurised first to bleed the system apart from if it's been done anyway to work on the system. As you say the the manual bleed screws can be used to fully depressurise the system if required though. You dont need a Lexia for the job (It may not be possible with Lexia anyway if the BHI is faulty.

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Re: c5 suspension pump refit

Post by cachaciero » 20 May 2009, 12:33

wheeler wrote:
cachaciero wrote:
sportingfiat wrote: I havn't yet worked out an easy way of pressurizing the resevoir so I did the following.
A normal cooling system pressure testing kit with various cap adaptors does the job perfect.

I dont see why the system needs to be de pressurised first to bleed the system apart from if it's been done anyway to work on the system. As you say the the manual bleed screws can be used to fully depressurise the system if required though. You dont need a Lexia for the job (It may not be possible with Lexia anyway if the BHI is faulty.
Unfortunately being a mere amateur I don't have a cooling system test kit either :-(.

I would beg to differ on the Lexia question, as I said you can depressurise the system using the manual bleed screws but doing it this way WILL let air into the system (unless the bleed screws have a Non Return Valve built in) which defeats the object of the exercise.
The Lexia way doesn't let air back into the system.

Having said that I don't know for sure that it makes a difference I just feel that it may, guess it depends on where any air bubbles end up.

Seems to me tha one of the best ways of bleeding the system may be to apply a vaccuum to the top of the resevoir thus causing any air to "fizz" to the top.

(Now a vac pump I do have :-)

Cachaciero.

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Post by AndersDK » 20 May 2009, 16:17

A pressure of 0.5bar is very easy obtained with a bicycle hand pump, and a standard bicycle air valve.

There is no need for elaborate checking if this pressure is correct as long as its not way too high or far too low.

I know nothing about the C5 pump and/or heght setting controls, so thats why my next question coming up :

Why would it be necessary to use a Lexia test station to inflate an empty C5 suspension system ?

The fluid is already lightly pressurised to help the pump prime and get started to pressurise the system.
The rest of the procedure is very well known as Citaerobics, from the green era of hydro Citroens.
This is the standard procedure to inflate a hydro Citroen - and vent out all air possibky residing from the suspension.

I may be terribly wrong - in which case I do hope someone will enlighten me (please !) - but it seems un-necessary complicated demanding a Lexia procedure to get a C5 up and running.

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Post by myglaren » 20 May 2009, 18:04

A bit vague on this but I do recall reading something about the Lexia opening some internal valves that are otherwise inaccessible.
It is also a necessity for properly bleeding the suspension as otherwise the ABS system can be damaged.

Can't verify this unfortunately.

One day I'll have to let Jim loose with his Lexia and see how much damage we can do to the system :D

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Post by sportingfiat » 20 May 2009, 18:58

knew it wouldnt be simple but dont think suspension can get any lower about on floor so gonna try changing it and see what happens

worse case means trip to dealer next week but least will be better ride lol

andy

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Post by cachaciero » 20 May 2009, 21:39

AndersDK wrote:A pressure of 0.5bar is very easy obtained with a bicycle hand pump, and a standard bicycle air valve.

There is no need for elaborate checking if this pressure is correct as long as its not way too high or far too low.

I know nothing about the C5 pump and/or heght setting controls, so thats why my next question coming up :

Why would it be necessary to use a Lexia test station to inflate an empty C5 suspension system ?

The fluid is already lightly pressurised to help the pump prime and get started to pressurise the system.
The rest of the procedure is very well known as Citaerobics, from the green era of hydro Citroens.
This is the standard procedure to inflate a hydro Citroen - and vent out all air possibky residing from the suspension.

I may be terribly wrong - in which case I do hope someone will enlighten me (please !) - but it seems un-necessary complicated demanding a Lexia procedure to get a C5 up and running.
Anders the problem with pressurisation is not finding a source of pressure, it's finding a way of connecting that source to the filler neck of the resevoir in an air tight manner ;-)

Think I shall buy a spare cap if not too expensive with a view to modifying it.

Although on reflection I feel that pressurising the resevoir would only be required after the system had been completely drained to prime the pump as you have observed.

As for venting the system the C5 (and C6) are different to older Citroens in one very important difference Hydractive 3!.
On the C5 when you select low suspension the car actually goes to a height which is commended by the pump WHICH IS NOT the maximum that the cylinder can go to, hence even at the lowest setting there can still be oil and /or air in the strut.
When you depressurise the suspension system from low it will actually drop about another 25mm in terms of actual road height.

On old Cits low really was at the max travel of the strut and you didn't depressurise the suspension as such you depressurised the main system pressure.

Now on the C5 as there is still pressure in the suspension system even on low you do have to depressurise the suspension system to safely work on it.

Now if you depressurise the system using the bleed screws yes the suspension will drop that last little bit and some oil / air will come out of the bleed screw unfortunately air will also get in through the bleed screw into the pipe work. When the system is then pressurised the air in the pipe will get pushed into the strut and will get compressed.

Going to high setting will push the bubble up to the end of the strut but when you go back to low that bubble will end up at the base of the strut because on low the strut piston is not completely at the end of the cylinder.
Needless to say this air bubble has a marked bad effect on the suspension as I have discovered.

Now using the Lexia depressurisation is achieved by forcing the return ElectroValve open thus the bubble gets forced back down the pipe back to the resevoir, there is no way additional air can get back into the system.

Frankly I am not absolutely sure that even using the Lexia will get all the air out of the system as the strut pressure and return line is the same bit of pipe back to the pump unit so if once the strut is at it's lowest mechanical level there is no air in the strut but there could still be air trapped in the pipe which will get pushed back into the strut as soon as the "up" EV is energised.

Hence my comment about applying a vacuum to suck the air out.

Certainly one thing I have discovered a relatively small amount of air in the oil will markedly transform the suspension characteristics, for the worse!

Cachaciero

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Post by AndersDK » 20 May 2009, 22:07

Thanks very much Cachaciero.

One important thing to remember doing the Citaerobics : it still does work perfectly, even not hitting the bumpstops by the completely empty cylinders.

The idea is to get the fluid moving back and forth thereby drawing the air back to the reservoir.

Another thing to keep in focus : the suspension cylinders have not been opened in their feed lines by using the bleed screws on a C5.
Meaning there wil not be drawn any noticeable amount of air downline to the cylinders.

I would certainly not fear doing a simple re-start of the pump unit.
Only thing that gould go wrong is warm running of the pump and hence a blown fuse.

I am certainly aware that the HA3 system is not exactly the Xantia system once and again. But still the basics apply ...
We just need some experience from owners who thinks this cant be that complicated.
After all the D models were just sbout stunning rocket science when they first appeared on the roads, until some sensible home mechanics started thinking ...

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Re: c5 suspension pump refit

Post by wheeler » 20 May 2009, 22:15

cachaciero wrote:I would beg to differ on the Lexia question, as I said you can depressurise the system using the manual bleed screws but doing it this way WILL let air into the system (unless the bleed screws have a Non Return Valve built in) which defeats the object of the exercise.
The Lexia way doesn't let air back into the system.
When manually depressurising the system you just use a piece of tube on the nipple & submerge the other end in some LDS. Just the same as you would when bleeding brakes. This will prevent air getting into the system.

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Re: c5 suspension pump refit

Post by cachaciero » 20 May 2009, 22:55

wheeler wrote:
cachaciero wrote:I would beg to differ on the Lexia question, as I said you can depressurise the system using the manual bleed screws but doing it this way WILL let air into the system (unless the bleed screws have a Non Return Valve built in) which defeats the object of the exercise.
The Lexia way doesn't let air back into the system.
When manually depressurising the system you just use a piece of tube on the nipple & submerge the other end in some LDS. Just the same as you would when bleeding brakes. This will prevent air getting into the system.
Good point, should have thought of that, braincell drop of coupled with years of working on what are essentially self bleeding systems.

Cachaciero

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Post by cachaciero » 21 May 2009, 00:44

AndersDK wrote:Thanks very much Cachaciero.

One important thing to remember doing the Citaerobics : it still does work perfectly, even not hitting the bumpstops by the completely empty cylinders.

The idea is to get the fluid moving back and forth thereby drawing the air back to the reservoir. ...
Might be a good idea but in my admittedly limited experience it doesn't work like that on the C5 I don't think the flow rates are high enough.
Another thing to keep in focus : the suspension cylinders have not been opened in their feed lines by using the bleed screws on a C5.
Meaning there wil not be drawn any noticeable amount of air downline to the cylinders. ..
Not true, there is only one line to the cylinder which is both feed and return, the bleed screws are effectively about half way down the pipe run from the BHI to the cyclinders where the single line from the BHI splits to each cyclinder.

I would certainly not fear doing a simple re-start of the pump unit.
Only thing that gould go wrong is warm running of the pump and hence a blown fuse...
In the context of this thread neither would I and at the end of the day even using simple techniques one should get something that works BUT unless done properly it won't be as good as it should be.

I am certainly aware that the HA3 system is not exactly the Xantia system once and again. But still the basics apply ...
We just need some experience from owners who thinks this cant be that complicated.
After all the D models were just sbout stunning rocket science when they first appeared on the roads, until some sensible home mechanics started thinking ...
Anders
In my working life I am a reasonably well respected " fix it" engineer on some pretty complicated pieces of kit which often end up in parts of the world where resources are not really adequate to keep them running as they should. So going back to basics and trying to find solutions to problems without all the developed worlds resources is second nature to me, but there comes a time when you have to acknowledge that some things just aint going to be fixed properly if at all with a penknife and a bit of string.

The C5 is not exactly the Xantia, or more familar to me the XM, it has similarities it's got four wheels and an engine and a broadly similar suspension system and that's about it.

The C5 in almost all of it's operation is so far removed in degrees of complexity from either of it's predecessors that before I purchased one I factored the cost of a Lexia into the finance. Yes there are some things that can be done without the Lexia but often not without risk of collateral damage or with not such a good result or just plain time consuming. Anybody that is going to purchase an older C5 and be serious about doing in depth maintenance should IMHO invest in a Lexia (PC version circa £300) otherwise find a good garage with some really competent engineers.

The father to this thread really demonstrates this.
Sportingfiat is changing the pump without really knowing for sure that the original is U/S, it probably is, you and I worked it through and came up with a likely "single failure case" explanation. However there are "double failure cases" of external components that could cause the same symptoms. Access to a Lexia would have positively identified what was wrong in a very short space of time, component substitution of things like BHI's even at secondhand prices can turn out to be a very expensive way of proving that there was nothing wrong with the original device.

Anyway back to the topic SportingFiat I really hope that your new pumps work for you look forward to hearing a positive result.

Cachaciero

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Post by sportingfiat » 22 May 2009, 20:32

pumps all on not too bad a job only problem i have now is no one can get hold of any lds oil :( anyone know anywhere in nottingham/derby who supplies it?

cheers
andy

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Post by AndersDK » 22 May 2009, 21:36

Must be a Citroen dealer not too far from you ?

Often the larger gas stations have a good variety of oil and fluid types for any possible motorised vehicle usage.
Must be the same in UK ?

Looking forward to read more reports from your project \:D/

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Post by sportingfiat » 22 May 2009, 22:18

looks like a trip to dealers in morning only 20 mins away so not too bad

2 litres of lds and 2-3 spare 40a maxi fuses and will see how she fairs :)

hoping its ok as need car desperate on tuesday for work lol


cheers