D front not rising
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  1. #1
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    Default D front not rising

    Dear brains trust

    My D special front suspension is not rising on start up.

    I have moved the lever to the various settings, and the rear is responding but not the front.

    There is no obvious LHM leak, and I have tried the bleed screw on the regulator.

    i assume that the most likely (without looking yet) diagnosis would be the push rod onto the height corrector.

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    Before I go about removing the guard etc (with the additonal challenge of not being able to raise the front end) is there anything else I should be considering?

    AM

  2. #2
    Real cars have hydraulics DoubleChevron's Avatar
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    Quote Originally Posted by ajaxvte View Post
    Dear brains trust

    My D special front suspension is not rising on start up.

    I have moved the lever to the various settings, and the rear is responding but not the front.

    There is no obvious LHM leak, and I have tried the bleed screw on the regulator.

    i assume that the most likely (without looking yet) diagnosis would be the push rod onto the height corrector.

    Before I go about removing the guard etc (with the additonal challenge of not being able to raise the front end) is there anything else I should be considering?

    AM
    I'm going to take a punt and say your simply low on LHM ... .does the pump start rattling after the back lifts Generally selecting high seem to over-ride selector issues and give you maximum height if there is issues there.
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  3. #3
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    No, sorry, should have said that I checked the LHM level. It is fine and the pump operates normally. The front refuses to budge.

  4. #4
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    Blocked LHM filter? Mine was like that before I cleaned it out.

    Sometimes jiggling the height lever would help. Clean the filter as a first point of call!

  5. #5
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    Quote Originally Posted by ajaxvte View Post
    Dear brains trust

    My D special front suspension is not rising on start up.

    I have moved the lever to the various settings, and the rear is responding but not the front.

    There is no obvious LHM leak, and I have tried the bleed screw on the regulator.

    i assume that the most likely (without looking yet) diagnosis would be the push rod onto the height corrector.

    Before I go about removing the guard etc (with the additonal challenge of not being able to raise the front end) is there anything else I should be considering?

    AM
    If the filter is clean and you have sufficient fluid then you need to look at

    1) The linkage going to the front HC - is it actually moving the HC's control piston when you put it in the 'normal' position.

    2) If it is then the problem could be internal to the HC. Typically what happens is that a piece of rubber from a line seal or particles from a blown front suspension sphere have blocked the small passage ways inside the HC.

    3) If it is not - then you need to find where the height control rod is binding. With the front fender off and the front mud shield removed you should be able to see where the problem is.

    There is another possibility - does the hydraulic low pressure light actually go 'off' or does it stay 'on'? If it fails to extinguish then you have a problem with either the PR or the pump - most likely the pump. That switch, if operating correctly, is calibrated to turn off when pressure is in the 900 to 1200 psi range.

    Steve

  6. #6
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    Many thanks to all. The filter is clean and there is plenty of LHM. The hydraulic low pressure light turns off as per normal (although I have noticed recently a tendency to go out after the rear rises but before or during the front rising).

    It look like a wing and guard off job to see what is going on, and whether it is the linkages/rod or something internal to the HC. I rebuilt it in April and the suspension has been operating well since. Back then the problem was the front suspension stuck on high. Now the problem is being stuck on low!

    What a pain. Might as well take the other wing off as well and attend to various small things (air ducts, cleaning up and replacing wiring connectors, headlight control rod connector etc) at the same time.

    AM

  7. #7
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    Quote Originally Posted by ajaxvte View Post
    Many thanks to all. The filter is clean and there is plenty of LHM. The hydraulic low pressure light turns off as per normal (although I have noticed recently a tendency to go out after the rear rises but before or during the front rising).

    It look like a wing and guard off job to see what is going on, and whether it is the linkages/rod or something internal to the HC. I rebuilt it in April and the suspension has been operating well since. Back then the problem was the front suspension stuck on high. Now the problem is being stuck on low!

    What a pain. Might as well take the other wing off as well and attend to various small things (air ducts, cleaning up and replacing wiring connectors, headlight control rod connector etc) at the same time.

    AM

    That would make sense if the front suspension circuit is not getting any pressure - for what ever the reason.

    The security/priority valve is set so that the brake accumulator (if present) preferentially receives pressure prior to the suspension circuits. Am not sure but I think RHD cars were the same as Euro spec cars in that the pressure warning light is attached to the brake controller. USA and, IIRC, Swiss bound cars had it attached to the security/priority valve (there may have been a few other markets also). In either case the rear of the car does not require all that much pressure in the suspension. So it can start to rise up with the light still 'on' as insufficient pressure exists to turn it off.

    When all is working as it should it will still happen - you just don't notice as much as the front will also just start to come up at the same time. And the length of time for the light to extinguish is longer as far more volume of fluid has to pumped to reach the switch's cut-off pressure.

    Steve
    Last edited by Citroenfan; 1st August 2014 at 01:52 AM.

  8. #8
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    Sometimes the clamp on the anti roll bar that is turned to reset the front height can slip. If someone has adjusted the front height in the past it can slip because the bolts for the clamp have special heads (not hex) and they're difficult to do up real tight. Happened to me and the car stayed in high position, guessing it may do same and stay in low.

    But if you uncover the height corrector and push/lever the end piece where the brass end of the rod from the roll bar sits, it ought to rise up with engine running.

    Marc
    Cheers, Marc.

    1987 CX GTi T2 Maikonics
    1972 SM 2.7 carb
    1972 DS21 EFI

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    Quote Originally Posted by marc61 View Post
    Sometimes the clamp on the anti roll bar that is turned to reset the front height can slip. If someone has adjusted the front height in the past it can slip because the bolts for the clamp have special heads (not hex) and they're difficult to do up real tight. Happened to me and the car stayed in high position, guessing it may do same and stay in low.

    But if you uncover the height corrector and push/lever the end piece where the brass end of the rod from the roll bar sits, it ought to rise up with engine running.

    Marc
    Hi Marc,

    The factory referred to them as a 'conical' bolt/screw and used them in a few places as 'safety' fasteners (the transmission bell housing to engine comes to mind). However they are a standard 7x1.0 thread and can be easily substituted with a standard 7x1.0 hex head bolt of the correct length if one does not have the Cit tool or an equivalent to properly loosen/tighten them.

    Hopefully his problem is just a mechanical one. If it turns out that the HC's slide valve is actually moving then it means that something is blocking the inlet port inside the unit. They are not all that hard to disassemble and clean, but does require a specially machined tool to access the by-pass passage way.

    One needs to keep in mind that the total movement of the HC's control valve from it lowest to highest suspension settings is only on the order of between 2 and 3 millimeters. So it does not take much 'crud' inside one of these suckers to either partially or completely block a passage way.

    Steve

  10. #10
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    There is a special socket to suit those odd rectangular headed bolts/setscrews used on the front rollbar. If you don't have it, you can fit a piece of welding rod into a regular socket and turn it that way as the rod acts as a cam on one face. It works, but is fiddly and it's very simple to change the four bolts on the rollbar clamps for a Allen/Hex setscrew. Whether you change it depends on the toolbox and thoughts on originality.

    One trap when fiddling with the rollbar is that it's easy to slightly laterally displace the clamp for the link rod to the corrector. The hook on the corrector is designed to accept the linkage from the rollbar in a particular lateral position with only a small amount of play. If the linkage pushes laterally on the corrector's hook, then it can make it bind up. That could happen if adjustment of the linkage has moved the clamp laterally or the rollbar has moved laterally where the bushes are worn (which they typically are, being forgotten items) or the clamps have shifted. If you replace the plastic bushes and follow the factory instructions to set the lateral position of the rollbar (lateral limit imposed by 2 special clamps against inner sides of the bushes), then the clamp for the HC linkage may then turn out to be in the wrong place. If the rollbar has too much lateral play due to wear of the bushes, then it would be possible for it to shift in use and affect the corrector operation randomly.
    Last edited by David S; 1st August 2014 at 01:11 PM.

  11. #11
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    Good tip about the welding rod in the socket. I replaced mine with hex bolts but found they just wouldn't hold the clamp tight enough so went back to the originals.

    It's a few years ago now but worth mentioning that when I inspected the domed brass tip on the end of the rod from the roll bar to the HC, it was quite badly worn. Its brazed on so with ample heat it can be detached. I measured the widest point, got a new one made and brazed that on. I expected it to make a big difference but it didn't really.
    Cheers, Marc.

    1987 CX GTi T2 Maikonics
    1972 SM 2.7 carb
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  12. #12
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    Success! (I think).

    Took the wing and guard off. There was no movement in the rod into the HC, and I couldn't leverage any with a gentle working of the space around the ball.

    So I took the HC out and cleaned and reassembled it (but not the by-pass pot section as I don't have the tool required). Even as I disassembled the central rod loosened and developed a normal "play".

    After messing about putting the thing back in, the car is now behaving normally, in response to the height control lever. I'll have to get someone to show me how the clamp on the anti-roll bar should be set, and how to adjust it.

    Otherwise, thanks again for the advice.

    AM

  13. #13
    1000+ Posts michaelr's Avatar
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    Well done!

    If you have not yet put the guard back on and feel like getting a bit more involved the tool for the "bypass pot" is easy to make by filing a slot in the end of a suitable sized rod. The stack of tiny shims and spacers is an ideal place for junk to accumulate.
    Michael
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    Quote Originally Posted by michaelr View Post
    Well done!

    If you have not yet put the guard back on and feel like getting a bit more involved the tool for the "bypass pot" is easy to make by filing a slot in the end of a suitable sized rod. The stack of tiny shims and spacers is an ideal place for junk to accumulate.


    The 'by-pass' circuit is just a dampening device to help prevent the system from reacting to quickly to input from the suspension. Even if completely 'clogged' it would not prevent the car from rising and riding at its normal height.

  15. #15
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    Quote Originally Posted by ajaxvte View Post
    Success! (I think).

    Took the wing and guard off. There was no movement in the rod into the HC, and I couldn't leverage any with a gentle working of the space around the ball.

    So I took the HC out and cleaned and reassembled it (but not the by-pass pot section as I don't have the tool required). Even as I disassembled the central rod loosened and developed a normal "play".

    After messing about putting the thing back in, the car is now behaving normally, in response to the height control lever. I'll have to get someone to show me how the clamp on the anti-roll bar should be set, and how to adjust it.

    Otherwise, thanks again for the advice.

    AM

    All that info is in 814. And it really helps to have access to a lift - though it can be done, if one is really careful, by driving the front of the car onto ramps. OTOH you really need to try and figure out why you could not move the control piston in the HC. Something was really binding up the mechanical side of things. If you don't the problem may very well come back.

  16. #16
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    Quote Originally Posted by Citroenfan View Post
    The 'by-pass' circuit is just a dampening device to help prevent the system from reacting to quickly to input from the suspension. Even if completely 'clogged' it would not prevent the car from rising and riding at its normal height.
    Quite right, it will not stop the car rising, but it is there for a purpose. If the spool valve was clogged there is a high likelihood that the damper needs attention too.

    A clogged damper will affect how the car reacts to load changes.
    Michael
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    Quote Originally Posted by michaelr View Post
    Quite right, it will not stop the car rising, but it is there for a purpose. If the spool valve was clogged there is a high likelihood that the damper needs attention too.

    A clogged damper will affect how the car reacts to load changes.

    Don't disagree - however from what was written I did not get the impression that there was actually anything wrong with the HC. Just the act of removing and replacing, for what ever reason, freed up the mechanical linkages. If that was the case then either your thoughts, or someone else's, about a problem with the pivot may be what was/is going on. And from the question about re-setting the control rod and ride height really points to that area as the source of what was is going on. IIRC he, at some point in the past, had a problem with the car not wanting to come down from its max height. So it seems logical to me that all of this is part and parcel of the original problem.

    Very early cars (prior to 5/62) did not have that damper circuit. Remember well my parents 61 ID and a 62 DS that I drove across the US in. Lots of fun when you climbed out as someone passing by could think that all 4 tires went flat in unison .

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    Hi Steve

    Just out interest what are the differences in a D with and without that damper circuit in place in the HC? Did Citroen introduce it because customers didn't like the original design? Would be interested to understand.

    Cheers

    Marc
    Cheers, Marc.

    1987 CX GTi T2 Maikonics
    1972 SM 2.7 carb
    1972 DS21 EFI

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    Quote Originally Posted by marc61 View Post
    Hi Steve Just out interest what are the differences in a D with and without that damper circuit in place in the HC? Did Citroen introduce it because customers didn't like the original design? Would be interested to understand. Cheers Marc
    Hi Marc, While I cannot remembering it happening to me (with my parents 61) IIRC the problem was related to the suspension sometimes 'over reacting' or trying to compensate when on roads with rolling bumps where there were relatively long oscillations between the valleys and peaks. IOW the system reacted as though the car had gained or lost weight when it really had not. The damping circuit very neatly prevented that from occurring. A few months later (5/63) they did away with the small and very thin shims that were in the 'stack' to allow small unrestricted fluid volume movement and replaced them with a 2mm hole on the outside edged of the shock body to allow the system to react to short/rapid movements of the wheels. FWIW that by-pass hole in the shock body is one of the principle reasons many feel/felt that the later cars do not ride as nicely as the earlier cars. Two things happened to cause the change. The first was that as the cars became a bit heavier and with more power the actual shock settings were stiffened a bit. The second change occurred when the fixed damper spheres arrived in either late 68 or early 69 to 70 (depending on market). With these units that by-pass hole was narrowed to 1.80mm front and 1.60mm for the rear. The removable units used the 2mm hole front and rear. To add a bit more confusion to the whole mess the first generation of fixed shock spheres used a retaining ring to hold the damper body in the neck of the sphere. I think only some markets saw these - we did not, to my knowledge, in the US. Then they started riveting them in place. Have no idea if the 'replaceable' dampers (as opposed to the adjustable type used to this point) had the same flow characteristics as the ones that where riveted in place. Steve
    Last edited by Citroenfan; 4th August 2014 at 10:44 AM.

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