Originally a suspected timing chain rattle that has snowballed!

Discussion in 'Engine' started by FunkyFez, Oct 2, 2008.

  1. FunkyFez

    FunkyFez Member

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    AMG was at the scammers today to have a suspected timing chain rattle looked into. After having the timing case off the chain and tensioner was given a clean bill of health.
    The dealership now has no idea where the rattle is originating from and wants a further 20 hours diagnostic time which involves taking the engine out and rebuilding! :eek:
    One of their suspicions is bottom end bearings, but surely this 'rattle' would be present all the time and not just at tickover.
    This is not what I’d class as a sick car. 99,000 miles, with full dealer history. It drives, stops and idles as it should, kicks down sweetly and goes like a proper AMG.
    Is my local dealer clutching at straws here looking for a big pay day, or have i actually bough a lemon? :confused:
    Advice and opinions desparately needed as i'm not willing to part with the guts of £3K on a suspicion.
     
  2. grober

    grober MB Club Veteran

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    A rattle at tickover might be a failing oil pump problem. When the engine is idling it may not be producing adequate oil flow to some bearing surfaces. As the revs increase it starts to pump more and the "starvation" noise goes away. Bottom end wear noise problems are normally described as a lower frequency "rumble" or knocking which doesn't sound like your problem? Does sounds more like timing gear related i.e. camshaft/followers. The other area that can give a rattle are worn gudgeon pins where the conrods connect to the pistons. There are lots of things to check before stripping an engine -the obvious ones oil and filter+ it might be worth trying an engine oil flush? next would be putting an accurate analogue gauge onto the oil gallery to monitor the oil pressure accurately to see if its still in spec. It might be an idea to replace the oil pump anyway as a precaution on an AMG engined car at 99k miles. Unfortunately even this relatively easy replacement on some cars probably means removing the engine from your car to remove the sump.
     
  3. SilverSaloon

    SilverSaloon MB Club Veteran

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    :eek:

    no idea on the problem, but sounds to me like you need to find a good SPECIALIST and get your car out of the dealers!!
     
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  4. Number_Cruncher

    Number_Cruncher Hardcore MB Enthusiast

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    The first thing I would do would be to record the noise onto a computer - then, by using a cheap/free sound file editing program, have a look at the waveform.

    If, say, your engine is ticking over at 600 rpm, and you see a peak in the waveform 10 times per second, you know that it is something happening once per rev.

    By doing this, you will be able to see if it's something happening at firing speed, at crank speed, at cam speed, at oil pump speed, or something that's more random.

    One other thing that I would do before embarking upon serious and expensive work is to check, very carefully, that there is no mis-firing, or rough running at idle. Does the Star machine allow cylinder balance (Morse) testing?

    Looking for a mis-fire sounds odd, but, even very slight rough running at idle can cause significant crank speed variations which can cause rattling of otherwise sound components.
     
  5. OP
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    FunkyFez

    FunkyFez Member

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    Scammer Report as Follows:

    "Checked for noise from engine traced noise to timing chain / sprocket area. Removed coil packs and leads removed rocker cover to inspect. Timing chain and tensioners appeared to have slight play.
    Chain possible streached.
    Further investigation required to identify exact cause. Will require to remove engine and strip front end on engine to access further investigation. Quote estimate £1727.25"

    My question is this:
    Timing chain identified as being streatched by technician. Should this not just be replaced as note above.
    Why is there requirement to remove engine? What else are they looking for?
    Indy for timing chain replacement?
     
  6. ukcodger

    ukcodger Hardcore MB Enthusiast

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    The dealer report does not seem to match up with your initial post. Have they in fact done further work because the dealer report still seems to be pointing to a chain issue? Or have they given you other information as per your 1st post?
     
  7. Will

    Will MB Club Veteran

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    How about taking this as an opportunity to upgrade - plenty of rusty/crashed E55s about for an engine transplant!! :devil:

    On a more sensible note, Grober/Numbercruncher's advice sounds pretty good. I like the idea of recording and analysing the engine rattle to work out where it originates.

    To be honest, the ~ £2K quote to remove and diagnose the fault would put me off a bit. How much then to repair the engine and replace? It'll still be essentially a 100K mile engine after all that.

    A replacement engine might well be a better long-term solution, normally these AMG V8s are quite tough - there's a CLK55 with nearly 200K miles on eBay somewhere, and also a 160K mile E55. Plenty over 100K with no engine problems AFAIK.

    Will
     
  8. jaymanek

    jaymanek Authorised Forum Sponsor Authorised Forum Sponsor

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    take it to an independent, at 9 years old, this is out of their depths.
     
  9. Satch

    Satch Hardcore MB Enthusiast

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    Are you talking about biscuit tin full o' spanners rattle or just a bit annoying?

    Full time or part time?

    Better when engine is warm?

    Oil change make any difference?
     
  10. stevesey

    stevesey Hardcore MB Enthusiast

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    What's a "quote estimate"? Its either a quote (binding) or a estimate (best guess).
     
  11. OP
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    FunkyFez

    FunkyFez Member

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    I sent it to the main dealer suspecting a timing chain and they have confirmed that it has some play, which in my opinion would warrant a replacement.
    The bottom end bearing suggestion seems to be somebody's opinion or excuse to remove and strip down the entire engine, which to be honest is not going to happen on my watch. It also doesn't sound like a rumble or knock as suggested before.
    I have since collected the car and settled the bill until i get some further advice / second opinion. They have also provided a report that reads as the previous post.
    The 'quote estimate' was a whole list of parts that the main dealer has listed to be replaced if the engine is to be stripped down, but the 'estimate' part doesn't account for any further parts that they feel need to be replaced once the V8 is a pile of bolts and they have a thorough inspection.
    To describe the noise, it is always present when the car is either hot or cold only to 1500 RPM (not audible when the automatic choke is out) and it's sounds like a chain running at high speed through a sprocket. Only ever on idle, but no effect of the overall running smoothness. If you were to reverse crank a mountain bike pedal the sound generated by that would be getting close to the mark, only faster and more lubricated. A stretched chain seems to be plausable.
    The main dealer have admitted that they have never changed a C43 timing chain, nor disassembled the engine and i'm not willing to fund a training exercise for their tech's or a maybe.
    I've probably answered my own quetion with describing it as a chain related noise, so that leads to the next:
    Would a slightly streatched chain fail or just keep flexing?
    Does anyody know a good Indy in Aberdeen?
    My local indy that has worked on the car before wasn't exactly sure on how to replace a chain, so i'll willingly travel to have this 'issue' rectified.
     
    Last edited: Oct 2, 2008
  12. Will

    Will MB Club Veteran

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    Have you asked them what the level of chain stretch is? Quite unusual for an AMG V8 to have a chain replaced (not saying it's not possible for it to be stretched, just that most engines don't rattle and they continue to run fine)

    Are you/they sure it's not just a weak tensioner or similar?

    Will
     
  13. Ian B Walker

    Ian B Walker MB Club Veteran

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    Has anyone thought of the oil pump drive chain tensioner? Broken spring and it will rattle like hell on tickover. Add some throttle and it will be kept taught.
     
  14. grober

    grober MB Club Veteran

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  15. Dieselman

    Dieselman Banned

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    Check the cam chain 'stretch' by removing the cam cover and turning the crank so the cam sprocket is at eh timing mark. Measure the amount of lead ahead of TDC the crank pulley has in degrees. IIRC 5 deg is the limit.

    Buy an engine stethoscope and listen round the engine. You should know very quickly which area the noise originates from, which can be hard to decide normally due to noise travelling in an open deck engine.
     
  16. jaymanek

    jaymanek Authorised Forum Sponsor Authorised Forum Sponsor

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    the cam adjuster sometimes causes rattle but this is usually only at a specific RPM...

    We have just replaced one at a cost of around £500 and the rattle had gone.
     
  17. Uberwagon

    Uberwagon Hardcore MB Enthusiast

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    If they don't know the origins of a rattle then explain to them how a stethoscope works, they should find it in minutes.

    Dave!
     
  18. sweeper

    sweeper Hardcore MB Enthusiast

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    going back to my motorbiking days, this sounds like classic timing chain noise, i don't know the layout of the merc v8, does it have one, two or three chains? a guess from me would be one of the tensioners or as above one of the cam adjusters (assuming it has them).
     

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