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Oil pressure and big ends/main bearings

Discussion in 'A3/S3 Forum (8L Chassis)' started by Omniquito, Sep 16, 2012.

  1. Omniquito
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    Omniquito Member

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    [Sep 16, 2012]
    Hi guys, noob question I think but here goes...

    What do main and big end bearings have to do with loss of oil pressure (if any) and why would a failing one of these cause loss of said oil pressure?

    Sorry for what is most likely a noob question but I haven't completely grasped my oil pressure issue and found remnants of what I think are bits of shell bearings in my pickup gauze...
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  3. superkarl
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    superkarl MAN OF STEEL

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    [Sep 16, 2012]
    loss of oil pressure means the bearings arent fed with as much oil, if any, leads to them getting hot and wearing, FAST!
    there is also damage to the head and turbo.
    if this does happen you will have severe knocking from the big ends, until eventually its ****s itself.

    low oil pressure is basically worse than AIDS
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  4. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Sep 16, 2012]
    Typically bearing failure is the result of loss of oil pressure... your oil pressure issue will haev caused the shells to run hot and destroy themselves... I would say the debris you have found is the result of the low oil pressure rather than the cause

    <tuffty/>
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  5. jimmcgee
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    jimmcgee Member

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    [Sep 16, 2012]
    Force Feed


    read this , basically , the main bearing goes , there is more room for the oil to piss through and you lose pressure , simplessss .
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  6. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Sep 16, 2012]
    FWIW, my old A4 was on 195k and had low oil pressure. The crank and bearings were spot on, the loss of presssure was simply down to the oil pump.

    If bits of bearing had disintegrated and made their way into the sump it'd be knocking like mad. Certainly wouldnt drive normally.
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  7. Omniquito
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    Omniquito Member

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    [Sep 16, 2012]
    Fantastic, thank you. I had a feeling the bearings could effect pressure.
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  8. Omniquito
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    Omniquito Member

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    [Sep 16, 2012]
    Thank you again for your awesomeness Aragorn!
    mines done 220k and when when it's cold and warm prior to oil pressure drop it's NOT knocking and the whole engine actually sounds pretty good tbh... Might get the pump done and the big ends whilst they are in there...
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  9. phil miller
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    phil miller Member

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    [Sep 16, 2012]
    havent read your link, but have to say you have got it bang on, when i was at college (20 yrs ago) they couldnt explain it as easy as that
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  10. Omniquito
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    Omniquito Member

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    [Sep 16, 2012]
    Just another quick question, my garage said he would never reuse a shell bearing once the cap was removed.

    What is your view on it? Can I undo and inspect and redo up a big end?

    Mind you, after re reading Jims post it's a main that will effect pressure and I can't reuse the bolts so can't inspect without buying new bolts....
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  11. boost-addict
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    boost-addict Member

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    [Sep 16, 2012]
    this all depends on how worn they are, say for example there 2mm stock and minimal wear point is 1.75mm and yours are 1.86mm

    then you may as well change them whule your looking. you can do big ends with just the sump off.
    but then you cant replace main bearings, or small ends,

    if you have lost pressure, personally would replace all bearings/shells plus oil pump
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  12. phil miller
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    phil miller Member

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    [Sep 16, 2012]
    you can reuse them any good mechanic will A, check the thickness and B know if there heaverly worn, you cant re-use the bolts but as they are pence its not really a problem, although i do know a mechanic that did re use the bolts and threadlocked them, he never had a problem but then they werent turbo'd engines so a little different TBH
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