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Citroen hydraulics - Khamsin, Bora, early Merak, late Indy

Discussion in 'Maserati' started by thecarnut, Jan 11, 2009.

  1. staatsof

    staatsof Five Time F1 World Champ
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    Mar 13, 2005
    58,376
    Fuggetaboutitland
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    Bob
    OK, well I heard all the giggles ... speaks volumes about the general perception and extreme ignorance. Especially when he talks about a mechanic having it for 2 years not fixing then it sits in you garage for years and a shark, er ah I'm sorry a GUY like Wayne comes along buys and fixes it in about a day. Yah sure Wayne ... :rolleyes: I've met Wayne a few times at small gatherings and he's nice guy in those surroundings. He genuinely knows quite a bit about a lot of cars just not this one. I think he was falling in love with his own voice and felt like he had to perform as expert for the audience so he improvised. Others on the panel made lots of snarky remarks and the audience laughed. You'd never get away with this for a Ferrari. I wish one of us had been there. It's might have been satisfying for the sake of the car to rip him a new one, in a polite and informative way, for being so ignorant. Someone should have prepped him with the right script.

    It does make one wonder about so much of the wisdom being imparted by automotive experts does it not?

    But I think you need to contact Haggarty about this and just have them delete the Bora segment. There's no fixing it IMHO. It belongs on the bloopers reel of automotive collecting, Wayne and the segment, not the car! :)
     
  2. thecarnut

    thecarnut Formula 3
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    Apr 22, 2006
    2,187
    Atlanta
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    The Car Nut
    I recently repaired two of the Bosch hydraulic cylinders and one switch on a Khamsin. These are used for headlight lift, seat height adjustment and pedal adjustment (on the Bora). Although the leaks were not severe they really bugged me since LHM is very slippery on a concrete floor.

    I decided to write a DYI article as it might help others, and help myself when I try to do this years from now and won't remember :)

    It is posted here on my website: http://thecarnut.com/Manuals/Hydraulic_cylinder_port_seal_replacement.pdf

    Ivan
     
    71Satisfaction likes this.
  3. highwaybora

    highwaybora Karting

    Jun 18, 2013
    113
    SoCal
    Bravo!

    Good call...

    Thanks for objective description, photos, et al
     
  4. Froggie

    Froggie Karting

    Sep 27, 2017
    103
    Belgium
    I have a question regarding fading resistance of hydraulic brakes using LHM.
    Such a system has the reputation of providing greatly improved braking power also during strong/repeated braking.
    I am not sure of the rationale of such a good fading resistance even when the rotors/pads are submitted to very high temperatures, if it is due to the very high pressure of the hydraulic fluid in the circuit avoiding its boiling, or because it would counteract pads outgassing pressure.
    Does anyone know what happens in case of extreme use bringing the rotors to red, such as e.g. during repeated strong brakings on a long and stiff downhill or during track use?
     
  5. staatsof

    staatsof Five Time F1 World Champ
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    Bob

    OK well I can help with this one a bit as I've race open road in a Bora though not a lot of braking with that but also I've done the tri oval at Pocono in mine and have seen one other guy drive his harder than I did there.

    He destroyed a set of junky aftermarket pads, they're Pantera pads and we drove to my house that evening and picked up my backup set of OEM pads which he used the next day and it was fine.
    I never had brake fade, pad issues or rotor problems on that track with my Bora.

    Can't speak to the outgassing issue but yes I suppose the higher pressure might inhibit boiling. But I also think you need to look into the characteristics of original LHM more and see what it's boiling point is. I do know that it's far less hygroscopic than brake fluid
    and have often wondered why all of braking systems done use this? That alone will raise it's boiling point in practical usage situations. When I disassembled my braking system after being in a museum for it's 1st 10 year of life I found zero evidence of moisture or corrosion. It's even better than silicone brake fluid.

    The Group 4 Thepenier Boras originally had the LHM brakes on them and one has since been converted to a standard braking system.

    At speed on the track the braking feel under such loads is much better than it is on normal streets at ration speeds! :)

    My opinion on the system is that you need to bleed it more often which I beleive is due to nitrogen microscopy over time leaking into the system through the accumulators bladders. If you don't the brakes get a bit grabby and can pull right or left until the nitrogen is fully compressed. That's an opinion based upon experience I have not scientifically proven it.

    Bob S.
     
  6. Froggie

    Froggie Karting

    Sep 27, 2017
    103
    Belgium
    Thank you Bob, very helpful comments.

    In the meantime I have found extensive info on the use of LHM and its physical/chemical properties.
    Unfortunately, most of that info is in French, because of the Citroen origin and main users.
    I attach however two interesting links with tables (you may go deeper by using the usual translators).
    http://www.hd19.net/technique/hydraulique/etude_liquides_hydrauliques.html
    http://arnaud.meunier.chez-alice.fr/fr/theo/2cv/tr-roul/frein.htm

    Basically the LHM does have a slightly higher boiling point (265°C instead of 260 °C for DOT 4 or 5) but such properties remain very stable because of the inherent chemical stability and low affinity of LHM to water, contrarily to DOT 5 and DOT 4 respectively.

    Add to that the high pressure in the hydraulic circuit and you get indeed a master combination for braking.
    Also worth noting is the fact that the LHM use was abandoned because of an European regulation on the years 2000's obliging to separate the fluid circuit for braking, which would have obliged Peugeot/Citroen to make additional R&D to optimise the previous hydraulic systems used for braking/suspension/steering.
    Pity...
    So let's preserve our LHM braking, it's a worthwile historical piece of well designed technology!
     
  7. highwaybora

    highwaybora Karting

    Jun 18, 2013
    113
    SoCal
    Hi, Ivan..

    Always interested in your observations, appreciative of your knowledge and website... Thanks!

    The LHM /Bosch component related resources of long back are not really now current--
    wondering if you can re-publish any/all updated inf0' ??

    Or, is there some part of your website that is LHM-specialized (or could be?)

    All the best,
    Ned Evans
    Bora '626



     
  8. barnfieldman

    barnfieldman Rookie

    Apr 18, 2006
    18
    After reading through this thread I was expecting to see the specific citroen bubble flare on the hard lines that go into khamsin steering rack and some of the connections to the brake spheres and other connections, however they are not. Does anyone definitively know what the pipe flare is on the hard lines (and the dimension of the pipe), and what the hard line nut type is as it appears to be an M9x1.25 which I think is citroen thread size but evidently not the citroen bubble flare? Also if anyone knows of suppliers of these nuts that would be appreciated.
    Regards
    Paul
     
  9. thecarnut

    thecarnut Formula 3
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    Apr 22, 2006
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  10. staatsof

    staatsof Five Time F1 World Champ
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    Mar 13, 2005
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    Bob
  11. belfry

    belfry Karting

    May 14, 2015
    106
    After not driving the car for about a month, I discovered that there was no clutch pedal pressure. I had had a clutch master cylinder leak for the past 18 months so I removed it and sent it to Pleiades for a refurb. I refitted it yesterday, but I’m not getting any pressure at the pedal. The headlights go up and down, I’ve bled the rear brakes, and have bleb the slave cylinders (with my wife pressing in the clutch, pressing the brake pedal and raising and lowering the headlights). But still no pressure at the pedal. Where should I look next please?


    Many thanks
     
  12. belfry

    belfry Karting

    May 14, 2015
    106
    Merak SS by the way
     
  13. 71Satisfaction

    71Satisfaction Formula Junior

    Jul 15, 2012
    578
    New York and Norway
    Full Name:
    Art
    I don't know the Merak as well as my Bora, so I'll start with the simplest question:
    - Is your clutch circuit even associated with the LHM system?
    By virtue of you saying there is a Master Cylinder leads me to suspect the LHM and clutch hydraulic circuits are separate - like my Bora.

    Let's start there.
    - Art
     
  14. 71Satisfaction

    71Satisfaction Formula Junior

    Jul 15, 2012
    578
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    Art
    I see you looked at and posted in the 'Merak LHM Clutch bleed' thread below also... in which case I have precious few suggestions.

    - Conventional Master Cylinders need to be bench-bled prior to installation. Maybe your does too?
    - Continue bleeding the system, let plenty of LHM flow through and out to the rear slave cylinder.
    - If you see ANY foam in the LHM you are bleeding too quickly, so slow the flow way down.
    - Send a PM directly to those F.Chat members who names appear in the 'Clutch bleed' thread.

    Hopefully others may chime in to clarify the process,
    - Art
     
  15. belfry

    belfry Karting

    May 14, 2015
    106
    Thanks Art. I think that the clutch system is connected to the LHM system as another post (here in the UK) suggests that to bleed the slave cylinder requires the brake pedal/Light pod raising and lowering procedure in order to generate sufficient pressure. Also, I cannot see another reservoir for the clutch system. I attach a diagram of the hydraulic system with the master cylinder in the bottom of the diagram in the centre number 51

    Image Unavailable, Please Login
     
  16. am117au

    am117au Karting

    Apr 22, 2014
    143
    Sydney Australia
    Full Name:
    Greg G
    Hi,
    Does anyone have an exploded parts view of the Merak clutch cylinder.
    Regards
    Greg
     
  17. Foncool

    Foncool Formula Junior

    Oct 27, 2011
    255
    As far as I remember only the Khamsin had LHM assisted clutch.
     
  18. belfry

    belfry Karting

    May 14, 2015
    106
    The clutch is now working again, through a combination of pumping the clutch and bleeding the slave cylinder.
    The fluid coming out of the bleed nipple is green, so I'm assuming it's LHM. Does anyone know for sure? My car is a 1977 Merak SS RHD, I wonder if euro cars had different clutch hydraulics?
    I attach a photo of the refurbished master cylinder
    Image Unavailable, Please Login
     
  19. boralogist

    boralogist Formula Junior

    Jun 21, 2005
    324

    http://www.bridgeclassiccars.co.uk/bleeding-merak-lhm-system/
     
  20. 71Satisfaction

    71Satisfaction Formula Junior

    Jul 15, 2012
    578
    New York and Norway
    Full Name:
    Art
    #145 71Satisfaction, Mar 10, 2019
    Last edited: Mar 10, 2019
    Glad you got it working, even if there isn't clarity in what was going on.

    In the diagram I see an ambiguity in the representation of the system - the gap between line number 52 and fitting number 121 - but if those are connected, then there is a pressurized connection to the clutch MC #51 and if you are getting anything green, it's definitely LHM.
    The clutch MC must be more of a valve that pressurizes the slave to release the clutch.

    Learn something new every day.
    - Art
     

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