E 300 td diesel knock

Discussion in 'Engine' started by runningman, Apr 25, 2014.

  1. runningman

    runningman Member

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    300 td
    1998 R reg 300 turbo diesel, 47000 genuine miles, FMBSH.

    replaced the 6 glow plugs because of bad starting (number 6 glow plug faulty) and now starts just fine. What i have notice is that it has developed what sounds like a diesel knock, this seemed to have coincided with replacing the glow plugs. It only knocks at idle and up to 1500 rpm, above this this rev range it runs smooth as silk (purrs). Let the revs settle back down and the knock returns at 1500 revs and below.
    There seems to be noss loss of power. My dad drove it up the street the day and i saw a little blueish smoke from exhaust, drive it hard through the gears and you cannot see any smoke in the rear view mirror. My dad said when he starts it first thing in the morning it puts out a little white smoke and he can smell diesel.
    Im a very handy DIYer with the spanners but want some advice before i take it apart.

    Regards
     
  2. E270 Owner

    E270 Owner Hardcore MB Enthusiast

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    Get the injectors tested.

    Google Diesel Bob

    £5.00 test per injector
     
  3. johnsco

    johnsco Hardcore MB Enthusiast

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    I've run two of these cars over the past 7 years.
    They are "ticky" at low revs.
    If you rev them from idle, it will disappear over about 1500rpm, then you will hear it again as the revs fall.
    One thing that increases the tickiness is air bubbles that can be seen in the many plastic pipes around the injector pump.
    The seals of the pipe joints do deteriorate periodically.
    Also the seal under the cap above the diesel pre-filter needs fitting with great care, or this can let air in.
    Also - Do not neglect the main fuel filter seal.
    This is quite a big area to seal, and again needs to be fitted with the greatest care.

    The additions of Millers diesel power eco-max to the fuel certainly quietens these cars down, and will help with cleaner-burn and injector-pump lubrication.
    Modern diesel fuels have less lubricity that in the past.

    I would be surprised if it was the injectors, unless they have been disturbed.
    I have owned two of these cars ... The first with 155000 miles on it when it was written off due to crash-damage ... My present one has 215000 miles on it and still goes like a train.
    I have never had to touch the injectors on any of them.

    I wish the glow plugs had been as long-lived !!
     
  4. spoton

    spoton Member

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    hydraulic damper

    does your engine have the hydraulic damper on the auxilliary belt tensioner, slightly worn bushings can cause a tappety sound at lower revs ,put your thumb on top of it see if the noise stops
     
  5. OP
    OP
    runningman

    runningman Member

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    Car:
    300 td
    been working on engine today. replaced all clear fuel hoses and filters using genuine parts. Had injectors refurbished and refitted them using new heat shields and the engine is still knocking the same, at idle and up to 1250 ish rpm, rev it up and it purrs away smooth as silk, revs drop and knocking returns.
    Checked the dampers and the harmonic balancer and all ok.
    Cracked each injector when engine revved at a steady 1250 rpm and the knock it still present.
    Removed the valve cover, and the chain and cams look brand new no signs of wear. If you remove oil filler cap when engine is running you can hear a definite knock. Ive used a stethoscope to listen to engine but can't locate the knock.
    What would case over fuelling? a faulty injector OR a faulty pump?
    I can't see it being any worn components because of the little mileage its covered.
    I changed the oil and filter in January using 5w 30 full synthetic and its done 3500 miles since, so im thinking its not the oil. maybe its a hydraulic lifter? ive used a wynnes hyd lifter treatment in the oil but it made no difference.
    This knock didn't developed, it happened suddenly following bad starting one morning, hence why I changed glow plugs.
    If you search youtube for 'Mercedes w210 e300 diesel engine sound injector' my engine sound very like it, but smoother at high revs.

    Regards
     
  6. OP
    OP
    runningman

    runningman Member

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    Are these engines sensitive to oil to correct viscosity, The service record indicates the dealership used various makes of oil over the years such as Castrol Edge, Shell and Mobile 1.
    I used Comma 5w 30 and have been told I should use 5w 40. if the knocking is caused by a hydraulic lifter would the thicker oil cure it?
     
  7. johnsco

    johnsco Hardcore MB Enthusiast

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    Any oil which satisfies the MB specification 229.1 will be OK.
    Personally, I have usually used a 10W40 semi-synthetic.
    However, there are 5W40 or 5W30 oils which are suitable.

    These engines are pretty-much bomb-proof.
    As long as you look after them, they are not troublesome.
    BUT
    They are ticky at low revs.

    Yours is low-mileage.
    Has it had its oil changes over the years ?

    That's one thing not to neglect.
    I've always done mine every 10000 miles.
     
  8. Dieselman

    Dieselman Banned

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    I would agree, here.
     
  9. Dieselman

    Dieselman Banned

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    I once had this issue. The engine sounded like it was splitting in half, but no diagnosing revealed why.
    It was definitely fuel related as if revved then allowed to fall back to idle it stopped until the fuel came back on.
    It then cleared up of it's own accord.
     
  10. peapod

    peapod Hardcore MB Enthusiast

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    I had the same noise and changed the injectors it did not fix it, I am sure air being sucked into the fuel system is contributory because the injection timing will move, delayed pressure rise with air in the lines to the injectors.

    Changing the seals in the pump discharge valves helped mine enormously with starting but I dont think helped with this rattle. Mine only rattles after a long hot run, I switched to semi synthetic and that helped a lot.
     
  11. Olivier

    Olivier Hardcore MB Enthusiast

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    I had few test with different engines, sometimes when you remove the oil cap there is a definite knock, MB didn't even know what it was on my previous one, sometime when you open the oil cap there is just a huff huff, no knock.
    I still don't know why? Nor did MB at the time?
     
  12. OP
    OP
    runningman

    runningman Member

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    after trying everything else i could think of, including new fuel system parts and injectors, i eventually advanced the pump timing. i dont know by how many degrees, i just listened to the engine until the knock dissapeared. It runs 99% ok now, but i will have to sort the problem eventually. i have noticed an increase in power and also the oil level has risen slightly, why?
    i get black smoke from exhaust when accellerating hard up through the gears, then it goes when cruising.
    still getting air in lowest pipe on the fuel shut off valve, all the other pipes are free from air bubbles. also noticed the lift pump was wet on the bottom were its bolted to the side of the pump.
    Does the lift pump just unbolt from the fuel pump or is there a procedure i must follow.
     
  13. Olivier

    Olivier Hardcore MB Enthusiast

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    Can you get the diagram about the fuel system (its somewhere in here) and tell us what pipe get air?
    Lift pump just unbolt, there will be some engine oil coming out once its out.
    If you remove the lift pump get the 2 diaphragms and the spring inside and change them. Why? Because why not ;P
     
  14. E270 Owner

    E270 Owner Hardcore MB Enthusiast

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    Over fueling after advancing the timing can damage the engine.












    .
     
    Last edited: May 19, 2014
  15. Lord-WYBMAnE220

    Lord-WYBMAnE220 Hardcore MB Enthusiast

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    If the timing change has resulted in increased partial combustion, unburnt fuel will be running down past the rings and into the sump.
     
  16. E270 Owner

    E270 Owner Hardcore MB Enthusiast

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    Of course hence the oil level rising.
     
  17. OP
    OP
    runningman

    runningman Member

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    spoke to a mercedes diesel specialist today and told him the full story.
    He says that the knock is caused by the dirty fuel valves in the top of the pump, resulting in insufficient fuel pressure reaching the injectors.
    The remedy is to remove each valve and clean and replace O rings, taking care that everything is metecliously cleaned.
    I adjusted timing back to its original position and the engine runs ok only a slight knock can be heard at 1000rpm!!!
    Wondering if running it advanced for a short while has somehow partially cleared the dirty valves. Going to run it for a few days see how it goes before i look at the fuel valves.
    As the oil is now contaminated with diesel and has done about 300 mile will any damage be done to the engine?
     
  18. E270 Owner

    E270 Owner Hardcore MB Enthusiast

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    Change the oil asap
     
  19. johnsco

    johnsco Hardcore MB Enthusiast

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    Sounds a plausible explanation.
    It may be that if you run the car for a while with something to clean your system, the problem may slowly go away.
    Refitting the diesel delivery valves is not for the faint-hearted.
    The most scrupulous cleanliness is essential.
    You are as-likely to make it worse as make it better.

    I have a slight leak on one of my diesel delivery valve seals --- But - I'm in no-hurry to do anything about it !!

    You will not have done any damage yet - But - Do change your engine oil.
     
  20. OP
    OP
    runningman

    runningman Member

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    Johnsco
    you say that im likely to make it worse than make it better if I attempt to clean the valves. Why?
    Is this a complex job?
    im a very handy DIY with the spanners and I understand that cleanliness is most important.
    Have you got any info you can share such as torque settings for the valves.
    Changing oil and filter this morning.
     
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