Citroen CX 2400 crankshaft bearings
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  1. #1
    Tadpole
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    Default Citroen CX 2400 crankshaft bearings

    Fellow Mechanics! Can I please have some advice about main and big end bearings for the 1978 Citroen CX 2400.

    The engine has been dismantled for the first time since manufacture. The journals for the main bearings on the crankshaft measure 64.035/04 millimetres, the bottom end of the range published in Haynes, i.e. 64.035 to 64.050 millimetres. All the journals for the connecting rods measure 53.990, the bottom end of the range 53.990 to 54.005. There is no ovality on any of the journals, though there is slight scoring on two or three.

    An experienced engineering firm has suggested I could get away with polishing the crankshaft anf fitting new standard bearings but would risk low oil pressure and has recommended regrinding the crankshaft.

    Is regrind of the crankshaft indicated?

    I have access to a supply of undersized bearings for 63.5 and 53.5 sized journals. This may be a reference to the Class B diameters published in Haynes: 63.535 to 63.550 for mains and 53.490 to 53.505 for connecting rods. The engineering firm has asked to know what "clearances" the bearings and crankshaft should have in the event that it has to regrind the crankshaft.

    The benefit of advice about whether or not to regrind and about clearances would be much appreciated!

    Ross Coldrey

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  2. #2
    Fellow Frogger! chez00's Avatar
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    I'm an automotive machinist, but still take my words with a pinch of salt.
    If it was mine I'd run the crank after a light linish with new standard bearings - you're still within factory limits so it'll be just fine. If you are worried about oil pressure, put a washer or two under the relief valve spring to compensate.
    1988 205 GTi XU10J4
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  3. #3
    Real cars have hydraulics DoubleChevron's Avatar
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    don't worry about oil pressure in a CX motor. It's huge. Alan S's son even found he could blow the seals on the oil filters due to the pressure the pump can create.

    Have you ever heard a knocking CX ?? Or heard of one with low oil pressure ever

    seeya,
    Shae L.
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  4. #4
    Tadpole
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    Default Thank you Chezoo

    Good Morning Chezoo

    Thank you for your prompt reply. I take it you are in the same business as that of the people who are advising me! Do you mean just a light polish and will that be enough to deal with the scoring? Actually, for a reason I am too embarrassed to explain, I am having to fit a brand new oil pump to the car, so at the least that part of the engine will be right up to the mark. Do you have anything more to add?

    Thank you.

    RGC

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    Tadpole
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    Default Thank you

    Good Morning Shae L

    Thank you for your reply. Actually what led me to stop driving the car and recondition the engine was a flickering oil pressure lamp. The engine on this car had not been dismantled since manufacture and, when I purchased it in 1991, showed signs of poor and rough maintenace. I am having to fit a new oil pump so perhaps that and new standard bearings will be enough. Of course I want to make the correct decision; just getting one of these engines out is quite a job, not to mention the overhaul itself.

    Cheers

    RGC

  6. #6
    1000+ Posts Greg C's Avatar
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    The flickering oil pressure light could have been just the oil pressure light switch. Sometimes it is a prelude to just letting go and dumping all the sump contents on the roadway.

    The CX bottom end is tough, I have never heard of anyone needing to grind the crankshaft
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    Hi Ross
    Having rebuilt last year (with the hands of a respected professional) a DS21 engine I can only concur that a fine linish of the journals will likely be sufficient. The engine had really suffered neglect. probably abuse and has come up well with a linish. Journal sizings were in the mid range of specification and consistent, such as you have indicated with your engine.

    In an ideal world, yes, regrinding the main and connecting rod journals would give perfect clearance for maximum oil pressure performance.
    In the real world of dealing with this situation, linishing will be effective with new standard bearings.
    Your crankshaft will have a marking of either X or Y to indicate the size range of the journals when manufactured.
    I have a factory manual for the CX on a series of PDF files. However, it is only volume 1, volume 2 has the guts of the job rather than pure measurements.
    From the measurements you have given, your engine is a Class A and will be marked with an X on the journal.
    The bearings you have are for a Class B engine, the crank would be marked Y.
    I do suspect the clearances wil be similar to that of the D series engines. If I can make the time I will check either today or tomorrow and PM an answer to you.

    Hope this helps.

  8. #8
    Real cars have hydraulics DoubleChevron's Avatar
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    Quote Originally Posted by Ross Coldrey View Post
    Good Morning Shae L

    Thank you for your reply. Actually what led me to stop driving the car and recondition the engine was a flickering oil pressure lamp. The engine on this car had not been dismantled since manufacture and, when I purchased it in 1991, showed signs of poor and rough maintenace. I am having to fit a new oil pump so perhaps that and new standard bearings will be enough. Of course I want to make the correct decision; just getting one of these engines out is quite a job, not to mention the overhaul itself.

    Cheers

    RGC
    Common problem. You need to change the oil pressure switch. It will be leaking (If you stick a pressure gauge in there I'm sure you'll find it's perfect).

    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

  9. #9
    Tadpole
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    Default Thank you

    Greetings Greg C, Richo and Double Chevron

    Many thanks for your advice, which is unanimous. It seems I need not have the crankshaft reground therefore will not.

    I am mystified by this word "linish/linishing." I would be very grateful to you for telling me what it refers to, for I will have to instruct the local engineering shop what to do. Does this just mean polishing? Whatever it means, that and standard bearings seem the way to go.

    Cheers

    RGC

  10. #10
    Tadpole
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    Default Data on Crankshafts

    The attached diagrams from Vol 2 of Repair Manual 818 CX Vehicles Feb 1976 may be of use

    Mike

    Whoops, having trouble reducing them in size to get through the filters

    Can email them separately if you desire them

    Mike

  11. #11
    VIP Sponsor richo's Avatar
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    That's the way forward Mike.
    I seem to only have volume 1, which without Volume 2 is not as useful.

    Ross,
    Linishing (usually performed after grinding) or polishing refining an already finished bearing surface) a crankshaft is explained with this link

    http://www.aera.org/ep/downloads/ep7...2009_52-54.pdf

    Hope this helps.

  12. #12
    Fellow Frogger! chez00's Avatar
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    I know very little about this specific model, but If it is the case that these engines are known to have decent oil pressure and your crank measures within specifications, you are doing no one any favors by grinding the crankshaft - best to keep it standard.
    1988 205 GTi XU10J4
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    Default Thank you

    Hello Mike Ford

    Many thanks for your message. Actually I found one of the Citroen technical manuals on the Internet yesterday and the dimensions it gave for the crankshaft journals for this engine are identical to those in Haynes, quoted in my original post.

    RGC

  14. #14
    Tadpole
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    Hello Richo

    Thank you for sending the article, which I read with interest. I suppose the engine reconditioning firm that I am dealing with, in business since 1963, will know what is required. This firm claimed the polish can be made without reduction in the dimensions. I do hope so; as I explained in my earlier e-mail, the dimensions of the main and connecting rod journals are at the bottom end of the allowable range. What intrigues me about that is the apparent complete absence of ovality of any of the journals; if the journals were worn then would signs of ovality not be present? However, the unanimous advice is not to regrind.

    RGC

  15. #15
    Too many posts! JohnW's Avatar
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    Quote Originally Posted by Ross Coldrey View Post
    Hello Richo

    Thank you for sending the article, which I read with interest. I suppose the engine reconditioning firm that I am dealing with, in business since 1963, will know what is required. This firm claimed the polish can be made without reduction in the dimensions. I do hope so; as I explained in my earlier e-mail, the dimensions of the main and connecting rod journals are at the bottom end of the allowable range. What intrigues me about that is the apparent complete absence of ovality of any of the journals; if the journals were worn then would signs of ovality not be present? However, the unanimous advice is not to regrind.

    RGC
    Maybe the wear is negligible and the crankshaft is as built, just in spec?

    I rebuilt a 150,000+ km Renault R8 motor years ago (haven't needed to touch it since) and the shaft was as new in journal dimensions, with the slightest hint of fine scoring. I just bolted it back together with new bearings (the old ones looked OK but it was apart!) and I still have the same 60 psi oil pressure 23 years later.
    JohnW

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  16. #16
    Tadpole
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    Good Morning John W

    Thank you for bothering to reply. Yes, I had the same thought. RGC

  17. #17
    VIP Sponsor richo's Avatar
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    Ross, the engineers will know what to do.
    No easily measurable amount of material will be removed by the process of polishing.
    Let them have at it, replace the oil pressure switch and reassemble carefully with the new standard bearings. Job done.

  18. #18
    Tadpole
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    Hello Richo and the other kind respondents

    Again thank you very much for following my enquiry and concern.

    RGC

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