front suspension fault

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tranentbx
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front suspension fault

Post by tranentbx » Fri Oct 02, 2015 6:39 pm

Good evening,

The front of my 14Re just sank very quickly to the floor.
No LHM leaks and it pumps back up fine and will hold its position. However if I push down it collapses again to the lowest setting and wont go up again. Do I blame the front height corrector? Return valve stuck open somewhere? Your thoughts are appreciated!

Thanks

Pascal

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ken newbold
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Re: front suspension fault

Post by ken newbold » Fri Oct 02, 2015 10:08 pm

It's either height corrector or front struts :-/
They think it's all over, it is now!

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Re: front suspension fault

Post by tranentbx » Sat Oct 03, 2015 6:37 am

Thanks Ken, both struts at once gone? Or would one knackered one mean the front cant hold its self up?

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Re: front suspension fault

Post by ken newbold » Sat Oct 03, 2015 10:42 am

Not sure, I wonder if they're passing lots of fluid in the ruturns, might pay to remove the return pipes and see if either one is passing fluid.
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Re: front suspension fault

Post by tranentbx » Sun Oct 04, 2015 8:21 am

Very odd thing has happened..... It's all completely back to normal. It rises and falls to all settings and stays there. It's keeping the expected bounce in the normal setting and behaved perfectly on a drive.

Is it just a random quirk of a 30 year old french car?! I think a valve must have stuck temporarily but has now freed itself. The car was unused for 4 weeks prior to that as I was away on holiday.

I also had a look at the height corrector on the pit. Seems to work as it should and looks set correctly. How much can go wrong with them?

Anyway, I'm just happy she's OK!

Thanks

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Re: front suspension fault

Post by Tinkley » Sun Oct 04, 2015 10:44 am

If you haven't already, might be worth flushing the system, at least replacing the fluid. Nominally every 35k for a change. Might be well worth as a minimum rebleeding the system, as it may just be trapped air. I've just done the rear arms on one and had a lot of trouble getting fluid to the n/s rear brake caliper. The car swallowed 1.5 ltr of LHM and it started on top indicated level at the tank!. After filling and refilling along with a few ups and downs and playing with the bleed screw pressure was restored properly and the brake bled.

As the car seemed to work OK before I did the arms, there was no reason to suspect a lack of fluid. However it shows how much fluid can be 'lost' in the system over time mostly with air. Probably just bouncing around and maybe not being bled properly. Whilst there is no technical service period to bleed a system, it is worth doing occassionally as everything works properly afterwards ie smoother suspension, progressive brakes etc. Also shifts any crap through and into the filter or through the brake bleed nipples.

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Re: front suspension fault

Post by Way2go » Sun Oct 04, 2015 1:05 pm

It is very unlikely that in an open and recirculating system like the BX that there is going to be any trapped air. The only exceptions being the blind ends of the brakes but this would not affect the suspension.
More likely that the symptoms described are due to a need of lubrication on the linkages of the height corrector. Use 3in1 penetrant spray and you usually will regain the 'magic carpet' ride. It is also more effective to spray this sideways from the wheelarch than from above in the engine bay.
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Re: front suspension fault

Post by Tinkley » Mon Oct 05, 2015 10:08 am

Well, I'd be amazed if one blind end of the rear brake system can take 1.5 ltr of LHM...... :wink:

Despite it being recirculating it is still possible for air to get into the system over time IMHO, and worth a bleed now and then.

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Re: front suspension fault

Post by Defender110 » Mon Oct 05, 2015 4:04 pm

Tinkley wrote: Despite it being recirculating it is still possible for air to get into the system over time IMHO, and worth a bleed now and then.
That would be a pointless exercise, you only need to bleed the system to purge the pump, once it is up and running it is continuous self bleeding and shouldn't get any air in the system if the fluid is at the correct level. Obviously if the fluid level is low it may drag air through the system as it sloshes about the reservoir but will still bleed itself out when the level is topped up. The blind brakelines can get trapped nitrogen in them from leaking spheres but that will not be release by a main system bleed.
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Re: front suspension fault

Post by Tinkley » Mon Oct 05, 2015 4:34 pm

Still does not solve the problem of starting on Full level in reservoir and needing 1.5 ltr + 150-200ml to bleed maybe 150-200ml out, to get brake working. So where has the other 1.5 ltr gone? Level in reservoir fell doing rise and fall etc, so had to be topped a couple of times. Meant there was air somewhere, I noted also the return into reservoir was very frothy. New car to me so I don't know it yet. My own belief is that over time, the suspension does return a frothy mix into the reservoir on occassions or it is created from slopping about on the very potholy roads round here and that does get pumped through. Hence some air does become trapped over time maybe in the pump but anywhere else it can too.

As I know the Octopus was changed last year on this car which is a good thing, and the fluid was all a nice bright green indicating freshness. If the same guy who did the Octopus was the one who fitted one of the brake pads the wrong way round so the piston could rotate (front o/s) it probably was not bled correctly after changing the tubing. How does the OP know how well bled his system is?

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Re: front suspension fault

Post by Defender110 » Mon Oct 05, 2015 9:47 pm

Tinkley wrote:Still does not solve the problem of starting on Full level in reservoir and needing 1.5 ltr + 150-200ml to bleed maybe 150-200ml out, to get brake working. So where has the other 1.5 ltr gone? Level in reservoir fell doing rise and fall etc, so had to be topped a couple of times. Meant there was air somewhere, I noted also the return into reservoir was very frothy. New car to me so I don't know it yet. My own belief is that over time, the suspension does return a frothy mix into the reservoir on occassions or it is created from slopping about on the very potholy roads round here
LHM is an antifoaming fluid so I can only suggest for your problem is perhaps it was filled with something other than LHM but the continuous flow system does not collect trapped air that can be bled out, all you would be doing by opening the bleed screw on a pumping system is losing the fluid. Any air in the system is pumped into the reservoir.
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Re: front suspension fault

Post by Tinkley » Tue Oct 06, 2015 7:01 am

We know the sytem is robust and fail safe, done too many miles in BX... must be around 280k now. But in this car only 30, and there were some interesting hammering noises from the pump ie air trapped until I'd bled the thing. I'm just suggesting the OP should do the same as his front suddenly failed to support the car.

I'm happy my latest aquisition has a full system now, when you don't know the history fully (fsh to 2006 but looked after since) it is wise to go through a few things. Next up is the water cooling and a full rad flush - nasty feeling it may need replacing, lot of surface rust at the cap housing. Also know that supplying dealer used to use tap water and I think it may never have been drained and replaced.

One car I bought had excellent water system cleanliness but the LHM was many years old (13?), pale yellow and original at 53k. We don't know the OP's car enough to know when the fluid was last changed and whether it was bled properly.

This one has some interesting crushing of the steel return pipes from the o/s front (after strut returns) where it appears the anti roll bar has knocked into the pipes as they follow the bend towards the engine bay. Never seen this before on a BX, but someone here will have had it.

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Re: front suspension fault

Post by Defender110 » Wed Oct 07, 2015 10:55 am

Tinkley wrote:We don't know the OP's car enough to know when the fluid was last changed and whether it was bled properly..
You don't seam to understand the main hydraulic system is a continuous circulating open system, it is not like a brake system where all the air has to be out of the system for it to work and you cannot fail to bleed it properly. When you open the priming screw on the main sytem you are only priming the pump. Once the pump is operational it's job is done, any gas /air then in the sytem will bleed itself out as the fluid is circulated through the reservoir. Opening the priming screw after the pump is operational will not bleed the system just loose you the fluid it pumps out. As I and 'Way to go' tried to explain it is "a pointless exercise" opening the priming screw to try and bleed it as any trapped air/hydrogen will bleed itself out as the fluid is circulated. As also stated hydrogen gas/air can get trapped in the closed ends of the brake system and need bleeding out at each wheel but not the fully circulating suspension system.
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Re: front suspension fault

Post by Tinkley » Wed Oct 07, 2015 6:14 pm

Defender110 wrote: You don't seam to understand the main hydraulic system is a continuous circulating open system, it is not like a brake system where all the air has to be out of the system for it to work and you cannot fail to bleed it properly. When you open the priming screw on the main sytem you are only priming the pump. Once the pump is operational it's job is done, any gas /air then in the sytem will bleed itself out as the fluid is circulated through the reservoir. Opening the priming screw after the pump is operational will not bleed the system just loose you the fluid it pumps out. As I and 'Way to go' tried to explain it is "a pointless exercise" opening the priming screw to try and bleed it as any trapped air/hydrogen will bleed itself out as the fluid is circulated. As also stated hydrogen gas/air can get trapped in the closed ends of the brake system and need bleeding out at each wheel but not the fully circulating suspension system.
I DO understand the system principle fine. I surmise that my 2 rear brake pipes now contain 1.5 Ltr of LHM..... :wink:

Actually you can fail to bleed it properly as several Citroen techs have told me and I have experienced. Actually harder to not bleed the brakes correctly to some extent.