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2.5 Tdi engine running badly - advice needed

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by uber-tub, Jun 19, 2010.

  1. uber-tub
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    uber-tub Member

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    [Jun 19, 2010]
    Hello all,
    Just bought a Cat D 2.5 TDi and the offside cambelt cover is missing. The car starts but runs very badly. There is a clatter, not unlike old diesel engines' 'diesel knock' but only when i lift off the gas.
    It will rev but only appears to be running on 4 cyl?!? I am concerned that the crash has caused the cam belt to jump a tooth of two. It has been say outside over winter... stood for 6 months waiting to clear insurance.
    Does anyone have any other ideas?
    Does anyone have any diagrams or info on cambelt timing marks?
    Regards
    mik
    #1
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  3. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Jun 19, 2010]
    Be patient.... No need to post in multiple locations.

    We have many diesel experts on here, you just need to wait for them to com online
    #2
  4. uber-tub
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    uber-tub Member

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    [Jun 21, 2010]
    Cheers Mark,
    wasn't sure i'd posed in the correct section...
    mik
    #3
  5. brownie 25
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    brownie 25 Member

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    [Jun 22, 2010]
    take off rocker covers some hydraulic tappets may be seized and some of the lifters may have fallen of.pull of your air box first doh and if there is a thumping sound like a Subaru i would say thats your problem.
    #4
  6. uber-tub
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    uber-tub Member

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    [Jun 23, 2010]
    cheers Brownie I'll check the followers. It does sound the most likely as I am now sure the cambelt has not jumped a tooth.
    cheers
    mik
    #5
  7. uber-tub
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    uber-tub Member

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    [Jul 1, 2010]
    Oh dear!!!!! I took off the rocker cover and saw a 'rocker' laid on it's side under the cam, and thought... 'okay, the spacer has fallen out and the rocker has fallen off'
    Then I saw two more rockers off. And three broken cam lobes! They look like chrome shims pressed onto a cast cam. Is this the case? Can they be repaired or is the cam scrap.
    Would a spacer falling out cause this damage, or it it more likely that I have three bent valves and a knackered head?
    Any ideas welcome.
    Cheers
    mik.
    #6
  8. brownie 25
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    brownie 25 Member

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    [Jul 1, 2010]
    not sure what you mean about lobes, there are things that sit on top of the tappets there small round things that the cams make contact with when there turning is that what you mean? are the cams worn where they make contact with the tappets my far left shaft was worst the last cam nearest the windscreen
    #7
  9. uber-tub
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    uber-tub Member

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    [Jul 1, 2010]
    By lobes I mean the egg-shaped profile on the cam which pushes the followers down. On my engine the cam lobes are a chrome sort of 'shim' pressed onto the cam, which I think means the cams are hollow and not cast, although they look cast.. I presume AUdi make them this way to reduce cost, but it seems they fail quite often... with pretty shocking results. I'm just hoping for no valve/head damage.
    We'll see soon enough...
    #8
  10. Turkster
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    Turkster Bro.Paul 2.5TDI Quattro Sport

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    [Jul 1, 2010]
    if i can just something here, 1 photo says a thousand words...............................

    show us what you see please :sos: then maybe we can advise you a bit better, it may not be as bad as you think,
    #9
  11. uber-tub
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    uber-tub Member

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    [Jul 1, 2010]
    i'll post a pic tomorrow.. good idea.
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  12. Turkster
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    Turkster Bro.Paul 2.5TDI Quattro Sport

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    [Jul 1, 2010]
    good lad :idea:
    #11
  13. uber-tub
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    uber-tub Member

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    [Jul 4, 2010]
    Right, some photos...
    Here is the roller rocker which shows the 'cup' that locates on the top of the hydraulic equaliser. This rocker was just rattling around loose in the head.
    [​IMG]

    this shows the cam in-situ with the rocker just laid loose.
    [​IMG]

    This shows the damage to the cam. The chrome 'cam lobe' snapped and half hanging off the cam.
    [​IMG]

    What could have caused this damage?
    I'm thinking the engine has been stood for 6 months so all the oil will have drained from the hydraulic equalisers ans if compressed they would not have re-pressureised... perhaps resulting in the rockers falling off and causing the damage to the cam?... or the cam has jumped a tooth and the valves have broken the cam? but this is the intake cam and there is no similar damage to the exhaust cam which is linked.
    I don't know... head off time?
    #12
  14. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    [Jul 5, 2010]
    The early 2.5's suffered from weak cams etc - the only time I've seen damage like that was from a skipped timing belt.
    #13
  15. brownie 25
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    brownie 25 Member

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    [Jul 5, 2010]
    the rockers on mine are one peace they dont have that roller on them.
    #14
  16. uber-tub
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    uber-tub Member

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    [Jul 6, 2010]
    skipped timing belt eh? Oh great!
    Vacuum test then head off I guess. Oh joy.
    thanks for replying.
    #15
  17. uber-tub
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    uber-tub Member

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    [Jul 9, 2010]
    ^^BUMP^^

    anyone any ideas what could have caused this damage.. (other than skipped belt)?
    I've seen plenty of examples of this damage on other forums but no one mentions how it was caused...
    #16
  18. uber-tub
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    uber-tub Member

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    [Jul 14, 2010]
    So here's the news for anyone interested. Audi have sent a replacement cam, but this one's solid! I queried why solid when the extg is hollow. Audi Bradford had no idea so they messaged Audi Germany. reply was that the cam design had changed, they are now solid (admission of design fault?) and there was no need to change the other hollow cams if they hadn't failed!
    Would have thought there'd be a balancing issue?
    #17
  19. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    [Jul 14, 2010]
    Hmmm thats pretty weird alright ....
    #18
  20. adamss24
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    adamss24 Well-Known Member

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    [Jul 14, 2010]
    Skipped timing belt and bent valves ! On the old design (early AFB, AKN, AKE) the rocker arms were cast and designed to break if the valves contacted the pistons then the valve spring would keep the valve shut without bending the valves. The cam would have no dammage whatsoever and i have rebuilt a dozen with just a few bent valves (ussualy 2-4) and a few shattered rocker arms just because of the better design. The later BDG,BDU, etc. with cam rollers were a bit more resistant to cam wear but would do much more damage because of the design and most likely the pistons would take a big hit... You're looking at a expensive rebuild if you have to pay someone elses labour costs...
    #19
  21. uber-tub
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    uber-tub Member

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    [Jul 14, 2010]
    Yeah it's a BDG... got three broken lobes on intake cam and three broken hydraulic equalisers on the exhaust.. all on cylinders 1,2,3. The more i think about it the more it looks like very bad news -like a skipped timing belt and bent valves. So to save my bank manager from an early grave I'm hoping to do as much work as I can with the help of an enlightened friend for the more technical aspects. If the head has to come off soon will I have to replace head bolts, and is it possible to buy a gasket kit for only one bank?
    I'll post some pics of any horrors I find. Will I have to have the valve seats ground to suit new valves?
    Forgive my ignorance...
    Cheers
    mik
    #20
  22. uber-tub
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    uber-tub Member

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    [Jul 14, 2010]
    Oh Lord! i've just re-read your post (adamss24)

    "...and most likely the pistons would take a big hit.."

    Holy kak on a stick. Motor in bits then...
    #21

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