CX Diravi problem?
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  1. #1
    Fellow Frogger! marc61's Avatar
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    Default CX Diravi problem?

    I replaced both track rods and had the tracking done a couple of weeks ago. Car drives much better than before, but it's still twitchy about the dead straight position. Steering governor is working properly and it firms up at speed, but at any speed a very slight movement of the steering wheel just a few degrees clockwise or anticlockwise is enough to move the car away from dead straight and head slightly to the left or right. When I take hands off the wheel it tracks dead straight but if I touch the wheel lightly it will come off dead straight.

    There is no play that I can find in the front wheels. There is play in the steering wheel when the cars been parked up for a while as usual, but absolutely none when the engine is running - the slightest movement of the steering wheel yields an immediate movement in the wheels.

    I'm wondering if it's a fault in the Diravi control unit. Is there a cam inside like on a D that keeps the wheel dead straight that it's no longer sitting in maybe? Failing that I'm thinking it's back to the tyre place and check the tracking again but I doubt it's that. Any suggestions much appreciated.

    Cheers

    Marc

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    Cheers, Marc.

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

  2. #2
    1000+ Posts gerrypro's Avatar
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    The plastic balls that control the slide valve in the steering control unit wear and give varied positions of the valve according to the range of slop. This slide valve apportions the pressure assistance to the rack. Could be the cause of the twitching!
    Fortunately the balls are easy to replace once the steering control unit is out!
    Cheers Gerry

  3. #3
    Fellow Frogger! marc61's Avatar
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    Thanks, I'll take the control unit out. Whereabouts are the little balls, how do you get at them to replace?
    Cheers, Marc.

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

  4. #4
    1000+ Posts gerrypro's Avatar
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    You need to remove the large rubber cover and disconnect the piping group. The Main aluminium body splits once the bolts are removed but Do not separate any of the gears inside they are sprung so that the maintain zero backlash and would be a pain in the neck to reassemble. ONE VERY IMPORTANT STEP. Before separating the casing a steel rod must be inserted into the hole under the steering column shaft to maintain alignment of the gears inside the casing. When the casing is apart you will see the slide valve and the governor arms with the plastic balls. They can be removed now and new ones inserted in their place.
    I had a look on line at CX Basis and could not find replacements. You may have to write to them or to Citroen Andre to get new ones. Western Hemispheres may also be a source, and then there is Andrew Brodie in the UK
    It also seems to me that they could be made with one of those new fangled 3D printers!
    Cheers Gerry

  5. #5
    Real cars have hydraulics DoubleChevron's Avatar
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    Before you go pulling the govener apart (though that does sound like the issue) check the steering rack subframe isn't cracked!

    seeya,
    Shane L.
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  6. #6
    1000+ Posts gerrypro's Avatar
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    We are not talking about the governor. We are talking about the steering control unit which is the proportioning device on the steering column!
    Yes cracks on the rack mounting plate should be checked before commencing more arduous work on the steering column!
    Cheers Gerry

  7. #7
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    The governor and ram pushing on the self-centering 'heart' inside the control unit are probably fine as it apparently stiffens up on the move etc.. If the balls inside the control unit are worn, then it may still self centre, but if you move the wheel, it could shift the rack control valve linkage in some unpredictable way. They tend to wander or become heavy when the balls are worn because the rack can't follow exactly where the driver wants it to be or can't do so quickly enough. You have to imagine two wheels that are meant to follow each other with a linkage between them moving a valve one way of the other off centre when the wheels are not aligned. When you turn the wheel, it moves the top wheel and the bottom is meant to follow when the rack moves. It's a form of feedback control. Very interesting, but awful to use when worn out.

    I think Roger Parker in Adelaide sell bits for them.

  8. #8
    Member twistedeez's Avatar
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    This is not yet an area of expertise but could you bleed the Diravi of possible air? There is a nipple on it. This was done to Cx recently and helped to improve the self centering. Easier than pulling it apart.
    Out of the 1992 Saab 900 turbo and into
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  9. #9
    1000+ Posts Ken W's Avatar
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    Having tackled one of these in my past, I think next time I might get a reconned exchange unit from Pleadies. There are absolutely stacks of tiny O rings in there that are sure to need replacing. How those little H linkage sets with the balls work so well has me beat.

    Cheers,

    Ken W

  10. #10
    Too many posts! JohnW's Avatar
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    Quote Originally Posted by DoubleChevron View Post
    Before you go pulling the govener apart (though that does sound like the issue) check the steering rack subframe isn't cracked!

    seeya,
    Shane L.
    Spot on. Mine was....
    JohnW

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  11. #11
    Fellow Frogger! marc61's Avatar
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    Quote Originally Posted by DoubleChevron View Post
    Before you go pulling the govener apart (though that does sound like the issue) check the steering rack subframe isn't cracked!

    seeya,
    Shane L.
    Just want to double check I'm looking for a crack in the brown sheet metal plate to which the steering rack is bolted? Presumably near the bolts?

    Thanks

    Marc
    Cheers, Marc.

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

  12. #12
    1000+ Posts gerrypro's Avatar
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    Quote Originally Posted by marc61 View Post
    Just want to double check I'm looking for a crack in the brown sheet metal plate to which the steering rack is bolted? Presumably near the bolts?

    Thanks

    Marc
    Yes, these plates do crack! And in the places you mention!
    Cheers Gerry

  13. #13
    Fellow Frogger! marc61's Avatar
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    Pleased to say have now solved the problem by swapping the Diravi unit with a second hand one. Had a fight with the ventilation tower to get it out, but after that it was a straightforward swap. Taking the bonnet off at the outset, so I could actually see what I was doing made things easier!

    There's a hole in the pinion nearest the rack into which a 6mm bolt or drill can be inserted to lock the wheels in the straight ahead position. In that way after reassembly once the engine is started the Diravi unit centres, then the 2 bolts to the coupling can be done up and the drill removed. Drove down the road minus the bonnet and everything was spot on, dead straight!

    Will look to take the original unit apart and see if the little balls have worn.

    Cheers

    Marc
    Cheers, Marc.

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

  14. #14
    Too many posts! JohnW's Avatar
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    Good to hear of a satisfactory result. When I bought my CX, I was told that the best way to work on them was to take off whatever was in the way rather than trying to do otherwise. I'd not thought of the bonnet in that context, but why not?

    Photos?

    Cheers
    JohnW

    Renault 4CV 1950 (R1062)
    Renault R8 1965 (R1130)
    Renault Scenic Series II 2005 (wife's)
    Renault Scenic Series II 2006 (daughter's)
    Renault Scenic Series II 2007 (mine)

    CitroŽn CX Pallas 1980 (moved on to new custodian)

    National Co-ordinator, Renault 4CV Register of Australia

  15. #15
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    Quote Originally Posted by marc61 View Post
    Pleased to say have now solved the problem by swapping the Diravi unit with a second hand one. Had a fight with the ventilation tower to get it out, but after that it was a straightforward swap. Taking the bonnet off at the outset, so I could actually see what I was doing made things easier!

    There's a hole in the pinion nearest the rack into which a 6mm bolt or drill can be inserted to lock the wheels in the straight ahead position. In that way after reassembly once the engine is started the Diravi unit centres, then the 2 bolts to the coupling can be done up and the drill removed. Drove down the road minus the bonnet and everything was spot on, dead straight!

    Will look to take the original unit apart and see if the little balls have worn.

    Cheers

    Marc
    Good result. The vent tower is possibly best removed, which can be a bit of a fiddle. You don't need to start the engine to set the centre point. You want a long rod (welding rod for example) that you insert into the hole in the control unit and through to the upper wheel and then keep going until you also lock the lower wheel. They both have a hole for that purpose. Then you can set the eccentric on the coupling to the middle of the range, centre the rack and secure it all. It should be very close then, but you may need to fiddle with the eccentric a little to adjust the tracking, which is why it's there. When you dismantle the old unit, don't lose any of the shims behind the valve block.

  16. #16
    Real cars have hydraulics DoubleChevron's Avatar
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    Quote Originally Posted by marc61 View Post
    Pleased to say have now solved the problem by swapping the Diravi unit with a second hand one. Had a fight with the ventilation tower to get it out, but after that it was a straightforward swap. Taking the bonnet off at the outset, so I could actually see what I was doing made things easier!

    There's a hole in the pinion nearest the rack into which a 6mm bolt or drill can be inserted to lock the wheels in the straight ahead position. In that way after reassembly once the engine is started the Diravi unit centres, then the 2 bolts to the coupling can be done up and the drill removed. Drove down the road minus the bonnet and everything was spot on, dead straight!

    Will look to take the original unit apart and see if the little balls have worn.

    Cheers

    Marc
    Does it still drive straight. The 6mm drill bit will center the rack, but it's highly unlikely the wheel alignment is set to straight ahead on the exact center of the racks travel (does that make sense ). If the car now steers to the left or right, turn both wheel alignment adjusters the equal amount until it drives straight. This will keep your alignment settings, but move the wheels back to the center of the rack ( if that makes sense ).

    seeya,
    Shane L.
    'Cit' homepage:
    Citroen Workshop
    Proper cars--
    '85 Series II CX2500 GTi Turbo I
    '63 ID19 http://www.aussiefrogs.com/forum/showthread.php?t=90325
    '72 DS21 ie 5spd pallas (last looked at ... about 15years ago)
    '78 GS1220 pallas
    '92 Range Rover Classic ... 5spd manual.

    Yay ... No Slugomatics


    Modern Junk:
    '07 Poogoe 407 HDi 6spd manual

  17. #17
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    What Shane is drawing attention to is the difference between the tracking of the steering gear and the alignment of the wheels relative to the rack. It's possible to have adjustment on adjustment that covers up an incorrectly setup unit. Overall, you need to arrange it so the control unit can come to its centre by itself, corresponding to the centre of the rack movement and the car runs in a straight line without the driver fighting against the hydraulics.

  18. #18
    1000+ Posts gerrypro's Avatar
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    In order to minimise the difference between the track rods, it is essential to have the rack end joints set exactly equal from the ends of the rack. The early rack with the silentbloc joint specifies this as 9mm +.7 - 0mm from the rack to the joint face before the lock nut is tightened. Then the adjustable sleeves have to be threaded onto the output and tie rod an equal amount of turns an preferably with equal length of thread inserted from each side. It is then possible to use a vernier depth gauge to check that the distance from the output joint of the rack to the steering swivel are exactly equal. With the rack locked at centre and the steering control unit locked with the rod through the centre of the unit all one has to do is bring the toe in setting to -1mm to -4mm. Everything then should be exactly set and at this point lock the flexible joint between the rack and the steering control unit!
    Last edited by gerrypro; 5th May 2014 at 07:04 PM.
    Cheers Gerry

  19. #19
    Fellow Frogger! marc61's Avatar
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    Yes the lets take the bonnet off to start with approach is what I used to do 30 odd years ago with GS's. Saves temper, backache and head banging!

    Its tracking very straight on the road but I was thinking maybe I should get the alignment checked again. However, like the idea of having a go with the verniers to see how equal things are left and right, will do that. Must admit having changed the control unit and stared at the rack and layout, this is a very very good steering arrangement, epitomises Citroen engineering!
    Cheers, Marc.

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

  20. #20
    Too many posts! JohnW's Avatar
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    Quote Originally Posted by marc61 View Post
    Yes the lets take the bonnet off to start with approach is what I used to do 30 odd years ago with GS's. Saves temper, backache and head banging!

    Its tracking very straight on the road but I was thinking maybe I should get the alignment checked again. However, like the idea of having a go with the verniers to see how equal things are left and right, will do that. Must admit having changed the control unit and stared at the rack and layout, this is a very very good steering arrangement, epitomises Citroen engineering!
    You haven't done anthing that would change the alignment have you? Apart from locking up on full lock when backing and filling to turn in tight spaces, I reckon the Diravi system is amazingly good. You'll never see such expensive ideas put into practice again.

    Nice result.

    Cheers
    JohnW

    Renault 4CV 1950 (R1062)
    Renault R8 1965 (R1130)
    Renault Scenic Series II 2005 (wife's)
    Renault Scenic Series II 2006 (daughter's)
    Renault Scenic Series II 2007 (mine)

    CitroŽn CX Pallas 1980 (moved on to new custodian)

    National Co-ordinator, Renault 4CV Register of Australia

  21. #21
    1000+ Posts gerrypro's Avatar
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    Quote Originally Posted by marc61 View Post
    Must admit having changed the control unit and stared at the rack and layout, this is a very very good steering arrangement, epitomises Citroen engineering!
    You are not wrong there!
    Cheers Gerry

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