Jumping BX

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Ian Fearn
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Jumping BX

Post by Ian Fearn »

Can anybody help with my BX front suspension?
The front end sticks like mad, when going from low to any other setting it jumps almost violently.
The front struts have been replaced with brand new genuine citroen ones and it still does it.
Also when it goes down it goes down in steps, each side is different. I assume the suspension should be lovely and smooth, any ideas?
tomsheppard
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Post by tomsheppard »

Sticky height corrector is likely to be a problem but!!!!!
Try the raising and lowering on level ground with the handbrake off before you draw conclusions.
A BX will lift quite sharply but due to the damping in the HC it tends to float downwards.
Each side is different. Frequently so. Friction in the rear arms? No, usually weight of driver. Jeremy is about. He's a bit of a whizz on height correctors. He may well have something to add.
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Post by DLM »

I can't remember how much space there is round the back of a GTi/TZi lump, but in a BX16 I used to own, it was possible (carefully) to reach down the back of the engine to the height corrector linkages. You can then move the linkage manually for test purposes and hence provide the right inputs to exercise the HC through its full travel. The linkage on this particular car was very sticky (it used to stick full down or full up) but after a bit of to-and-fro it was much improved.
Just a thought - when did you last change the LHM and clean out the tank?
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Post by jeremy »

Ian The BX suspension should be lovely and smooth in its operation. There is no hard and fast rule which end should rise first, my BX TD Estate sticks its nose in the air and eventually lifts the back but this is due to too many tools in the back!
The height correctors are vital to the correct functioning of the system and must operate smoothly and allow the car to settle at the correct height. The vital bit is the rod going into the corrector and when you find it you will probably find it is dry and rusted. The best suggestion for greasing it I have seen is to use a brush and some grease - I will do mine that way next time but the spray grease I aimed roughly at it last time is still working. To find the corrector follow the linkage from the anti-roll bar until you find a small cylindrical device with some hydraulic pipework, linkage etc. They are in the same place on all cars but obviously some engine bays are more crowded than others.
It is important that the rest of the height control linkage is well lubricated and free and the back corrector should be similarily treated. The design of the Citroen suspension is suck that the system functions over a relatively small travel as it doesn't need excess travel to compensate for load. The result is that if the car is riding say 1 inch low at the front it is in fact very near the stop and this is of course noticed in ride comfort!
I'm surprised that your car seems to behave differently from each side. Normally I would suggest sticking front strut but yours are new - an alternative could be rear arm bearings but I expect they are good as well otherwise you wouldn't have bothered to do the front struts. A possibility is air in the system - try Citroebics - raise and lower the car fully a few times.
jeremy
tomsheppard
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Post by tomsheppard »

Another thought. Worn rear struts?
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Post by jeremy »

Possible Tom - but I've never heard of it. I had a look at the ones on my Estate at about 180,000 miles - no leakage, no apparent noise - in fact very uninteresting! We never seem to get any queries about them on here (spheres and removal yes) so I assume that its the side thrust which destroys the struts.
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Post by tomsheppard »

When a BX sinks, the front usually touches down first and the rear tends to fall in jerky movements which I have always ascribed to wear on the sliding part of the rear strut. I'll be able to put the theory into practice before long as I now have a pair of new rear struts for the estate. As new fronts were fitted recently, together with rear arm bearings, this should give some idea whether it holds water.
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Post by bxbodger »

The front struts on mine have always been a bit sticky and jerky, no matter how much fiddling and lubing they have had.
I think it's just a crap piece of design, doing it McPherson strut style for cheapness, and the struts will be built down to a price, rather than up to a quality-the BX was designed with the mass market in mind and fleet buyers are more interested in cost than smoothness!! Its a better ride than,say, an escort, but its nowhere near as good as it could be had the accountants not been involved, but then again, it is the car that saved Citroen!!!
Earlier Hydraulic Cits use a more complicated ( and therefore expensive to produce ) wishbone variant which seems to work a lot better, and BL Hydragas was laid out similarly; it gives a much smoother front end than a strut ever will.
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AndersDK
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Post by AndersDK »

Brand new genuine BX front struts MUST have been on stock for ages. Thus very likely to be dry internally.
The HC would never cause this symptom.
Try Tom's idea on how Lubing front struts
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Ian Fearn
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Post by Ian Fearn »

Thanks for the replies.
I'm not totally convinced its my struts. They make no odd noises at all.
What would be the symptons if the height correctors were stuck up? It does seem strange that one side operates differently to the other.
LHM wise, i've not changed it but its had probably 5 litres of LHM after work thats been carried out so whats in the system is good. I've done loads of citrobatics to no avail, would it make any difference if i ran a load of hydroflush through?
The rear arm bearings have been changed and the rear suspension rises and falls beautifully.
Could it have anything to do with a dodgy doseur valve? I know that needs replacing next....
alan s
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Post by alan s »

When I hear of anything happening suspension wise one side but not the other, I usually immediately discount hydraulics as I fail to see how they can be involved. Front against rear I can follow, but not side to side as everything works on an interconnected system at front and rear, so if it was up at the front but down at the rear, that's feasible and common but not say down on one rear wheel but up on the other.
I'd be starting at bearings and bushes looking for possible seizures or alternatively incorrectly set pre-loads.
Rule of thumb on pre-loads is usually that whatever is being tested will move smoothly using one hand. If it just flops down, it's too loose and if it takes a lot of effort, 2 hands or leverage, it's too tight. I have been told also by "those in the know" that the use of moly grease in bearings is considered a nono these days as they claim in time it will eventually act like a wedge and restrict the movement of bearings particularly in things like swing arm bearings where they move back & orth rather than in a circular motion.
Just a couple of "maybe's" to consider.
Alan S
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Post by jeremy »

Thinking back a couple of years to when I changed my NSF strut for a new Citroen one (GSF Supplied) I do recall putting a few drops of oil on the exposed steel shaft through the hole in the sphere mount as it seemed slightly stiff and I thought the bearing might be dry. The one the other side is about 20,000 miles older and has had the same treatment too. Don't use too much oil otherwise the MOT man will think the strut is leaking!
Tom has a better method for lubricating the internals - I'm sure it is in Tips and tricks.
There is only one height corrector per axle and there should be no difference between the sides unless something mechanical is sticking.
Why do you think the doseur needs changeing? Unless it is leaking externally all that happens is the rear of the car drops a bit quickly and you will join those of us who have blamed it, replaced it and find the rear still drops as quickly!
jeremy
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Ian Fearn
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Post by Ian Fearn »

So the general thoughts on this then is if lubing the struts doesnt work then look for bearing problesm? Which bearings???
Although i still think its suspension related. The back end operates VERY smoothly up and down
The back end drops quickly but the brakes are leathal, blow on the pedal and you hit the windscreen. Its got progressively worse since i've had it, hence doseur valve thoughts?
jeremy
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Post by jeremy »

If the struts are ok yhen you are looking for friction in the rest of the suspension. The track control arm (wishbone) has rubbers on its inside end so unless they have been assembled with loads of pre-load they should only become looser with deterioration.
I suppose the ball joint at the outer end could sieze or ridge which might cause problems. Jack the car up securely on the bodywork and see if you can raise and lower the wheel with the control lever in the high position (correctors open). I suppose this could account for the car behaving differently on each side.
these joints do fail and are difficult to get out of the hub carrier. You may be able to grease them - it is possible to get a hypodermic needle attached to a grease nipple for injecting into sealed joint boots.
jeremy
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Post by yangreen »

Regarding lethal brakes, have you been driving the 2cv too much? Modern brakes are always a shock, especially the BX. I remember locking up all four wheels on dry tarmac once when someone pulled out in front of me. A straight stall as I couldn't get the clutch down quick enough!
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