CX question

[wuvvum]

OK, so the CX is up for its test at the end of the month and, being a CX, will need various bits doing, most of which are fairly straightforward. The suspension is behaving a bit funny, though, and as it's not a behaviour that I've come across in my previous CX's I'm not sure what's causing it. The ride is wonderfully soft, so the individual wheel spheres are all OK, but the back end sags quite sharply when I accelerate hard - to the point that all I can see in the rear view mirror is tarmac. I've tried standing on the towbar with the engine running, and the car immediately sags a good six inches (even with my skinny frame) and then around three seconds later it pumps itself back level. Also when the engine is switched off the back sinks very quickly (as in it's fully down within about half an hour, and sinks noticeably in the time it takes to fill up with petrol and pay), although the front stays up for ages which makes it look rather silly when parked. It definitely shouldn't be behaving like this, and I'm sure one of the many suspension components is defective, but does anybody know which one? Apart from anything else, it's making me hesitate to use it as a tow car - that degree of saggage on acceleration could ground the front of a trailer out.

[Guest Tony Hayers]

Try lubing the rear height corrector first. Bloody good soaking with WD40, lots of "citaerobics" and then grease it up.Im not sure if the CX has a rear 'accumulator' sphere (in the centre of the car) but if it does it may be this that has gone.My knowledge of hydro cits only goes as deep as the 2 Xantia that I have had, sorry that I cant pinpoint a direct answer to the problem.

[GrumpyOldMan]

Jetronic is right, the problem area is probably the rear height corrector. Give the linkages a good clean plus some grease, and the problem should be solved. The presence of air in the hydraulic system is another possibility. The 'citrobics' are a good solution for that (put the car on minimum height, then maximum height, then minimum again, and repeat for 4-5 times).If the above fail, the CX Club forum is an excellent source of help, and they have quite a few pictorials on how to refurbish the various parts of the suspension.Hydropneumatic Citroens before the Xantia didn't have the third 'anti-dive' sphere on the rear axle, and therefore do sag quite quickly after the engine is off (and the hydraulic pressure drops). In my experience, a flush of the hydraulic system and a change of LHM will improve things, but only temporarily. So you should probably just get used to it, considering it as part of the car's charm (along with the rust, electrical problems, high fuel consumption etc.)

[j-j]

Hello - I forgot you had a CX!The behavior on acceleration sounds like an excessive version of the normal behavior. The rear end squat is a characteristic of all pre BX hydraulic Cits where the spring rates were very much softer. The other reason is that the hydro suspension has 'rising rate' springs - meaning that the more compressed, the 'firmer' they get. It means that the initial rate is immensely soft but later ramps up for loading reasons etc. All hydraulic Citroens from the 1971 GS up to the XM had 'anti dive' suspension but this refers to the geometry of the front suspension and nothing to do with the hydraulics. Having said that! yours sounds excessive - I'd have to ask you what CX year and type it is? as the saloons squat more than estates and different types have different spring firmness also when the suspension rear spheres were changed and did you fit them or was it someone else. With that amount of soft travel in the suspension, the spheres are not flat but they might be the wrong ones for the rear of a CX (eg, if a garage fitted front ones on the rear it might behave like that). Any air in the rear suspension would be compressed to such a small tiny bubble at the pressures it runs that it wouldn't affect the actual suspension softness(though if there's air in the brake circuit at the rear it can cause the arse end to hit the deck under braking - this just needs the brakes bled)As for the sinking after switch off - you're right, there's no 'anti sink' on the CX (or any hydro Cit prior to 1995 - including the first Xantias) and it does sound like it sinks too quickly. You can check the rear suspension boots - these have a 'leakage return' plastic pipe and a vent pipe fitted into them. The vent is black coloured and the leakage is clear (after giving a good clean) - if you take off a wheel and carefully pull out the leak pipe to see how much LHM leaks from the boot you can see if there's an excessive collection in there indicating the rear struts are worn out (unlikely tho) Second point of leakage is the rear height corrector valve itself - but checking it properly needs laborious pressure gauge testing so it's best to just get a manual and find which of the return pipes at the tank is the one for the rear corrector and check its flow with the engine recently off over say 10 minutes. But I'd put my money on the brake valve! the rear brake circuit gets its working pressure off the rear suspension so that it's variable with load carried. The brake valve called a 'Doseur' can be known to leak the rear suspension pressure (mostly on post 1985 cars) while all the parts of the rear suspension are in fine fettle. Best test again is to find the return pipes from the brake doseur and try to observe excess leakage back to the tank.If it is the brake valve then I can put you in touch with a guy who can source a cheap replacement (same for any other CX part!)Let us know how you get on!G

[wuvvum]

(along with the rust, electrical problems, high fuel consumption etc.)

Actually it does have some rust (well, OK, quite a lot), but the electrics are spot on (touch wood...) and I've been getting up to 40mpg on a run, which I think is bloody good considering.Thanks for the suggestions guys. The car's a 1984 20RE saloon, so might be fairly softly sprung as standard - most of my CXs have been estates, and the only other saloon I've had was a GTI Turbo which was probably more firmly sprung anyway.I'll dig out the old Haynes manual and have a look at the items y'all suggested over the bank holiday, weather permitting.