2CV Bolt. What were they thinking?
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    Fellow Frogger! pottsy's Avatar
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    Default 2CV Bolt. What were they thinking?

    As we all know, Citroen are a lateral thinking bunch of Gauls, but lately I've been questioning their sanity somewhat.

    Firstly, I'm aware that there is an element of Citroeniste out there who view any minute variation from "Factory" as deviation of the worst sort and will perhaps react with a degree of pious fervour to my query, however, I've never subscribed to such illogical shenanigans so their protestations will be water off a Duck's back, so to speak.

    There are many areas of 2CV design which have my hand agitating my follicles, but the latest one seems to take the flat baked confection.

    The rocker shafts on the head are held at the top by the head bolts, but at the bottom by a Citroen Special Bolt with a head on it like a diseased pimple. Why is it so? I ask, summoning the Professor from my childhood.

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    The head on this bolt is a rounded rectangle 6mm wide and 8mm long. Nominally it requires a special tool to remove and replace. In a pinch one can improvise with adjustable spanners or vice-grips, but we really shouldn't need to resort to these methods. I've had a go at milling out the end of a bolt to suit but unfortunately the ageing motor on the mill threw in the towel. A job for another day.

    The business end of the bolt is simply 35mm of high tensile M8 x 1.25 thread. Experiment and a bit of Internet searching shows me that a socket headed capscrew of the matching thread is a perfectly adequate subsitute.

    The head clears the rocker cover, the function is the same and as a bonus a standard tool will operate it.

    Yet the usual suspects, sorry, suppliers, offer a special tool for this head as a matter of course so obviously people do remove and replace them.

    So can anyone shed some historical light on this conundrum? I doubt that Walter Becchia was such a devious designer that he did it out of spite. Surely there's a reason, but it's really not obvious to this retiree.

    Thoughts people?

    Cheers, Pottsy.
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    pottsy,
    you've hit the nail square on the head, since those peg bolts are a complete PITA.
    Replace with M8 cap head Allen screws, 35mm long, that's all...
    .
    ...except to say, avoid stainless screws.
    It took some time to extract a set of those from a pair of cylinder heads.


    Quote Originally Posted by pottsy View Post
    Thoughts, people?
    Cheers, Pottsy.

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    Fellow Frogger! citroenthusiast's Avatar
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    Quote Originally Posted by Ken H View Post
    pottsy,
    ...except to say, avoid stainless screws.
    It took some time to extract a set of those from a pair of cylinder heads.
    Now I am curious. What happened with the stainless screws? I would think stainless steel, being relatively non reactive would be a reasonable choice.
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    Cheers,
    John T.

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    Seem to remember that two of the bell housing bolts on the traction are a similar dimension. David Gries had tool that fitted in a socket wrench. It looked like flattened 'cylinder'!
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    Fellow Frogger! neural revolt's Avatar
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    Quote Originally Posted by citroenthusiast View Post
    Now I am curious. What happened with the stainless screws? I would think stainless steel, being relatively non reactive would be a reasonable choice.
    I think it could be a problem with galvanic action between aluminium and stainless steel. Could this be relevant to 2CV heads?
    I know we had this problem with radar antennas at Sydney airport; the s/s bolts became frozen into the aluminium antenna frames.
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    My guess would be that lethal pairing which is far too common, 'brute force' plus 'ignorance'.
    Whenever I install Allen screws for this application, I use the same torque as specified for the cylinder head stud nuts; 2.5 kgf.m / 18 lb.ft., less an allowance for oiled threads.
    However, it would be very easy for someone who considers torque wrenches to be an irrelevance to apply something close to double that torque...



    Quote Originally Posted by citroenthusiast View Post
    Now I am curious. What happened with the stainless screws? I would think stainless steel, being relatively non reactive would be a reasonable choice.

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    Quote Originally Posted by neural revolt View Post
    I think it could be a problem with galvanic action between aluminium and stainless steel. Could this be relevant to 2CV heads?
    I know we had this problem with radar antennas at Sydney airport; the s/s bolts became frozen into the aluminium antenna frames.
    That sounds about right to me. It's along time ago, but doing high voltage substation construction, you never had direct contact between stainless and aluminium due galvanic action. Galv to aluminum seemed to be ok through

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    Quote Originally Posted by pottsy View Post
    The rocker shafts on the head are held at the top by the head bolts, but at the bottom by a Citroen Special Bolt with a head on it like a diseased pimple. Why is it so? I ask, summoning the Professor from my childhood.

    The head on this bolt is a rounded rectangle 6mm wide and 8mm long. Nominally it requires a special tool to remove and replace.
    Are you any wiser on this Pottsy? On the DS, one (or two?) bolts holding the bell housing to the gear box (or the whole lot to the engine?) have 'special heads'. I'd assumed that these were meant to be 'tamper-proof' but why that would need to be case I can't imagine! I'd also be interested in the reason for your 'special' rocker bolt.

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    Err, for a galvanic cell to exist, don't the dissimilar metals need to be immersed in an electrolyte?
    If your engine oil is dosed with enough (saline?) water to render it conductive, you've got quite a problem...

    Quote Originally Posted by andrewj View Post
    That sounds about right to me. It's along time ago, but doing high voltage substation construction, you never had direct contact between stainless and aluminium due galvanic action. Galv to aluminum seemed to be ok through
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    Pottsy

    The galvanic voltage difference between two dissimilar metals is given by a chart such as that given in this article: SSINA: Stainless Steel: Corrosion

    Between stainless and aluminium will oxidize (protecting the stainless even more) formed. An electrical path between the stainless and aluminiumneeds to exist and and access to oxygen. Process is accelerated in corrosive conditions.

    In non corrosive connditions it is fine with the galvanic potential barely above aluminium and brass which is pretty universal in engines.

    You might consider the strength difference between stainless bolts and non stainless. It is possible to get Allen headed bolts up to grade 12.9 in non stainless.
    - you will be lucky to get half that in stainless steel.

    I would assume the old citroen bolts to be around 8.8 grade.

    I have the same views on citroen querks - some are brilliant some are questionable - sometimes it takes some time to figure out the category.

    Alex
    Last edited by Arekisir; 15th October 2017 at 08:14 AM.

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    SS can be a double whammy.

    Apart from the galvanic reaction, has anyone tried to drill SS?

    I used SS rivnuts to attach the floor on an old land rover. Installing them with compressed air always puts a strain on the thread, and, sure enough, one stripped. No way I could drill it out! I had to put a bolt in.

    I shudder at the thought of a SS bolt snapped off in a cylinder head.
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    Quote Originally Posted by geodon View Post
    SS can be a double whammy.

    Apart from the galvanic reaction, has anyone tried to drill SS?

    I used SS rivnuts to attach the floor on an old land rover. Installing them with compressed air always puts a strain on the thread, and, sure enough, one stripped. No way I could drill it out! I had to put a bolt in.

    I shudder at the thought of a SS bolt snapped off in a cylinder head.
    Hi geodon
    There are several types of SS and they are not the same properties. I would have to brush up a bit to say more. but generally the corrosion resistant ones are a bit soft but some types are hardenable and can hold a sharp edge in a knife for instance.

    The softer type will "work harden" the surface very quickly if you attack it, with for example, a blunt drill and speed. The surface work hardenes as you go and the drill gets blunter and it all turns to sh*t rapidly as the drill turns blue as does the air The trick is to sharpen the drill first, and then using a slowish speed and pressure and lubricant, ensure it cuts in and does not rub and continues to cut till you are finished the hole. Easy peasy
    Jaahn
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    These threads strongly resemble a game of Chinese Whispers sometimes!

    I'm not sure why this degenerated into a discussion on the relative merits of stainless steel over the real stuff, but "knowledge is no burden" as a wise person once quoth so I consider myself further educated.

    Anyway, I've taken on board Ken's wise suggestion of replacement of the diseased pimples with socket heads (normal high tensile steel) and then addressed the creation of a special tool for the removal of said pimples.

    After having a play with the large Mill that recently arrived in the Family, activities were suspended when the aging motor on the big beast decided to take a sabbatical, so milling operations were postponed. My thought was to mill an 8mm x 6mm slot in the end of a bolt, and this is certainly what the purveyors of special tools provide, in essence at least.

    However, sometimes inspiration strikes, so this morning I dug out a bolt of a meaty size and cut a 6mm slot in the end. Naturally I put a nut on first so I could run it back over the thread. after slotting. My thought was that the nut would stop the sides of the slot spreading under load, and this is exactly the case.

    Quite proud of meself actually. It seems to work and will only be needed to extract the PITA bolts anyway.

    Another Special Tool created here at the Bureau!

    In case you want to emulate my creativity, here's a couple of happy snaps.

    Cheers, Pottsy
    Attached Thumbnails Attached Thumbnails 2CV Bolt. What were they thinking?-square-bolt.jpg   2CV Bolt. What were they thinking?-square-bolt-tool-1.jpg   2CV Bolt. What were they thinking?-square-bolt-tool-2.jpg  
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    1982 ex UK 2CV6 ("Gaston") On the road! (Woohoo!)
    Half of a 1984 2CV6Special ("The Alleged Vehicle")
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    1000+ Posts gerrypro's Avatar
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    Those bolts are used in Traction bell housings and, also on the front suspension adjusters albeit in a much larger sizes. I know of a fellow who recently purchased an 11BL where the front torsion bars were incorrectly fitted and now that adjuster with the flats sits so far into the cross-member that it cannot be reached with the usual shifting spanner to turn it. And now that he has the need to reset the torsion bars the concept you have "invented" may be of use to him! Thanks Pottsy!
    Last edited by gerrypro; 21st October 2017 at 01:12 PM.
    Cheers Gerry

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    Fellow Frogger! pottsy's Avatar
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    Hmm. Hold off cracking the Veuve Cliquot, the concept may be slightly flawed.

    I've just tried the fancy new tool on Gaston and I first of all can't move those bloody bolts at all, and secondly both the bolt heads have rounded off slightly and the tool has "opened out" internally to cause the rounding.

    Perhaps I need to start again only this time harden the bolt end first (after cutting of course).

    The other issue seems to have compounded the rounding in that the nut I've used doesn't allow the slot to fully engage on the PITA bolt. (I'm going to adopt Ken's name for them, sounds better than diseased pimple!)

    Sadly, trying an adjustable spanner hasn't worked yet either, so I'll hold off until I come up with a more workable solution.

    Cheers for now, Pottsy.
    Buvito Ergo Sum!

    The Fleet:

    2006 307 Auto 5 Door ("Spike" Mrs P's)
    1974 D Special Manual Sedan ("Moby Dick")
    2006 C5 HDI Wagon Auto ("Mephistopheles")
    1957 Slough 2CV ("Alphonse") Waiting in the wings
    1982 ex UK 2CV6 ("Gaston") On the road! (Woohoo!)
    Half of a 1984 2CV6Special ("The Alleged Vehicle")
    And for Fun, 1968 Mini Deluxe ("The R & D'luxe" 1078cc, Grin Factor 100!)

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    Or, just buy a shock absorber stem wrench...

    https://www.zoro.com/cta-manufacturi...CABEgJ0afD_BwE
    Cheers,
    John T.

    61DS19 LHM BVH (son's); 67DS21 BVH; 71DS21 BVH; 73SM 3.0; 73SM EFI (Megasquirt); 73SM 3.0 (other son's)

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    1000+ Posts gerrypro's Avatar
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    Quote Originally Posted by pottsy View Post
    Hmm. Hold off cracking the Veuve Cliquot, the concept may be slightly flawed.

    I've just tried the fancy new tool on Gaston and I first of all can't move those bloody bolts at all, and secondly both the bolt heads have rounded off slightly and the tool has "opened out" internally to cause the rounding.

    Perhaps I need to start again only this time harden the bolt end first (after cutting of course).

    The other issue seems to have compounded the rounding in that the nut I've used doesn't allow the slot to fully engage on the PITA bolt. (I'm going to adopt Ken's name for them, sounds better than diseased pimple!)

    Sadly, trying an adjustable spanner hasn't worked yet either, so I'll hold off until I come up with a more workable solution.

    Cheers for now, Pottsy.
    For the ones I have encountered on the TA Bell Housing I have found that I can usually get them undone with a 6mm open ended spanner. Occasionally they have required some encouragement from a hammer and cold chisel! ( of course that approach is to be frowned upon. )
    Cheers Gerry

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    Fellow Frogger! pottsy's Avatar
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    Well I'll be Mogadored John T! Such a thing actually exists!

    Can't say I've ever heard of it, having always used vice grips or an adjustable spanner on shockers in the past.

    Looks like I may need to investigate further!

    Thanks, Pottsy.
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    Buvito Ergo Sum!

    The Fleet:

    2006 307 Auto 5 Door ("Spike" Mrs P's)
    1974 D Special Manual Sedan ("Moby Dick")
    2006 C5 HDI Wagon Auto ("Mephistopheles")
    1957 Slough 2CV ("Alphonse") Waiting in the wings
    1982 ex UK 2CV6 ("Gaston") On the road! (Woohoo!)
    Half of a 1984 2CV6Special ("The Alleged Vehicle")
    And for Fun, 1968 Mini Deluxe ("The R & D'luxe" 1078cc, Grin Factor 100!)

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    Quote Originally Posted by citroenthusiast View Post
    Or, just buy a shock absorber stem wrench...

    https://www.zoro.com/cta-manufacturi...CABEgJ0afD_BwE
    I think you can get brake adjusting sockets that are very similar? John: do you have one of these? if so, are they the right size to go over the end of the Mirex buckles used with Ligarex strapping

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    The stem wrenches come in different sizes, so you have to get the right one for the particular job. The one I have fits the M7 "tamper proof" bolts used on DS clutch housing and the anti-roll bar clamp. Other sizes may do other jobs.
    Cheers,
    John T.

    61DS19 LHM BVH (son's); 67DS21 BVH; 71DS21 BVH; 73SM 3.0; 73SM EFI (Megasquirt); 73SM 3.0 (other son's)

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    1000+ Posts gerrypro's Avatar
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    Quote Originally Posted by citroenthusiast View Post
    Or, just buy a shock absorber stem wrench...

    https://www.zoro.com/cta-manufacturi...CABEgJ0afD_BwE
    John I cannot get this link to work! All I get is something about the site being blocked in my country!
    Cheers Gerry

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    Quote Originally Posted by gerrypro View Post
    John I cannot get this link to work! All I get is something about the site being blocked in my country!
    https://www.vektools.com.au/lisle-sh...er-socket.html
    I guess this is the tool?

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    Quote Originally Posted by Harley View Post
    Thanks! I have ordered one!
    Cheers Gerry

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    Wow. I'd never heard of such a tool. Many thanks for yet another interesting thread.
    JohnW

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    Quote Originally Posted by gerrypro View Post
    John I cannot get this link to work! All I get is something about the site being blocked in my country!
    Sorry, I was entertaining family yesterday. It looks like you figured it out, though. If all else fails, you can just Google "shock absorber stem wrench" and get lots of options.
    Cheers,
    John T.

    61DS19 LHM BVH (son's); 67DS21 BVH; 71DS21 BVH; 73SM 3.0; 73SM EFI (Megasquirt); 73SM 3.0 (other son's)

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