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Thread: Piston Slap?

  1. #1
    Join Date
    Feb 2007
    Location
    sydney
    Posts
    239

    Piston Slap?

    Hi All,

    Bit of a hard one with the Musso.

    For several thousand kms now there is a distinctive rattle/knocking/tapping on startup (sometimes). Car has 170K on it now. this goes away shortly after giving a few more revs.

    Have always used good quality oil and new filter every 5000km. Went to a heavier grade oil recently which may have helped a little.

    What I have noticed though is something which seems SVO related. When running on blend the noise is often less noticeable or not there but i quite distinctive when i run on straight diesel.

    this leads me to think that its actually coming from the IP and the vege is quietening it down, or...

    If piston slap, the SWO may be changing the timing a little?

    Appreciate any thoughts, especially from those with Merc engines.

    Laurie

  2. #2
    Join Date
    Sep 2005
    Location
    WA
    Posts
    4,042

    Re: Piston Slap?

    Laurie,
    You could also have injector 'nailing'. I would think that Piston slap would normally be associated with low compression & blow-by. The fact that it changes with a Veggie-blend Vs Diesel supports this.
    I agree that Veggie could change the timing of injection.

    Let's see what others think.

    Tony
    Life is a journey, with problems to solve, lessons to learn, but most of all, experiences to enjoy.

    Current Vehicles in stable:
    '85 Mercedes Benz W123 300CD Turbodiesel single tank using 95% used cooking oil and 5% to 10% misfuel.
    '06 Musso Sports Crew Cab. Running on used cooking oil with 5% to 10% misfuel (where someone had filled diesel vehicle with petrol)
    Toyota Camry Hybrid - Wife's Car)

    Previous Vehicles:
    '90 Mazda Capella. (2000 - 2003) My first Fatmobile. Converted to fun on veggie oil with a 2 tank setup. Died when supercharger stuck at max boost for weeks. Stretched head bolts.
    '80 Mercedes 300D. 2 tank conversion [Sold]
    '84 Mercedes 300D. 2 tank conversion replaced engine with rebuilt OM617A turbodiesel engine. Finally had good power. Donor for current Fatmobile coupe.(body parted out and carcass sold for scrap.)
    '99 Mercedes W202 C250 Turbodiesel (my darling Wife's car) [sold]
    '98 Mercedes W202 C250 Turbodiesel (my car)[sold]



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  3. #3
    Join Date
    Jul 2008
    Location
    Logan QLD
    Posts
    20

    Re: Piston Slap?

    Hi all i would think it is an injector issue mine has the same KM's on it and needed a good gut full of cleaner thought it and that seems to have have fixed it for the moment. I also saw a post on a forum that the nozzles should be changed at ~100,000 KM's or so.

    Ossie

  4. #4
    Join Date
    Dec 2006
    Location
    Townsville, North Queensland
    Posts
    610

    Re: Piston Slap?

    A diesel with 170 k on it. It's hardly run in so I can't see it having piston slap that soon in it's life. Ya sure it's not the normal diesel knock that some engines seem to produce louder than others.

  5. #5
    Join Date
    Aug 2014
    Location
    Newcastle
    Posts
    22

    Re: Piston Slap?

    Big end knock?

    How's your oil pressure?

  6. #6
    Join Date
    Feb 2007
    Location
    sydney
    Posts
    239

    Re: Piston Slap?

    Thanks for the responses guys.

    After some more observation I've noted that the rattle is inconsistent. Often not there on wvo or only for a few seconds after a cold start up.
    Its much more pronounced when starting on dino and lasts longer up to 30 secs or so. Even then however no sign of it on hot start ups/
    Compression and oil pressure are good. As Qwarla said, it should really only just be run in after 170k and it goes better than it ever has with plenty of power. No signs of low oil pressure at start up.
    Ossie its been my understanding after many years of using wvo that the vege oil not only lubricates better but also has some fuel system cleaning properties. Not sure if a fuel cleaner will do much but certainly open to advice.
    I now thinks its unlikely to be piston slap or bottom end wear. I also think its unlikely to be top end engine wear and more likely to do with the IP and most probably an injector issue.
    Its a very intermittent noise and then mainly only on start up or at idle. Is this a symptom of an injector or would you think that if an injector was clogged or partially blocked that the symptom would be there all the time?
    Its a tinny/ rattling sound best way I can describe it.
    I guess I could crack each injector line individually and try to identify if this eliminates the sound.
    The Navara has 350K and I've never touched the injectors.
    Laurie

  7. #7
    Join Date
    Sep 2005
    Location
    WA
    Posts
    4,042

    Re: Piston Slap?

    Have the injectors serviced. This sounds like injector 'nailing' (the sound of a hammer hitting a nail).
    After 350K they in need of an overhaul. Normally the overhaul interval is 100K.

    Regards,
    Tony
    Life is a journey, with problems to solve, lessons to learn, but most of all, experiences to enjoy.

    Current Vehicles in stable:
    '85 Mercedes Benz W123 300CD Turbodiesel single tank using 95% used cooking oil and 5% to 10% misfuel.
    '06 Musso Sports Crew Cab. Running on used cooking oil with 5% to 10% misfuel (where someone had filled diesel vehicle with petrol)
    Toyota Camry Hybrid - Wife's Car)

    Previous Vehicles:
    '90 Mazda Capella. (2000 - 2003) My first Fatmobile. Converted to fun on veggie oil with a 2 tank setup. Died when supercharger stuck at max boost for weeks. Stretched head bolts.
    '80 Mercedes 300D. 2 tank conversion [Sold]
    '84 Mercedes 300D. 2 tank conversion replaced engine with rebuilt OM617A turbodiesel engine. Finally had good power. Donor for current Fatmobile coupe.(body parted out and carcass sold for scrap.)
    '99 Mercedes W202 C250 Turbodiesel (my darling Wife's car) [sold]
    '98 Mercedes W202 C250 Turbodiesel (my car)[sold]



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    Adding images and/or documents to your posts


  8. #8
    Join Date
    Feb 2007
    Location
    sydney
    Posts
    239

    Re: Piston Slap?

    Sorry Tony,
    I didn't explain clearly.
    The 350K is on my old Navara.
    The Musso Sports has the issue and it has 170K however thinking that its probably an injector issue.
    Laurie

  9. #9
    Join Date
    Dec 2006
    Location
    Townsville, North Queensland
    Posts
    610

    Re: Piston Slap?

    Just re reading ths post.

    What I have noticed though is something which seems SVO related. When running on blend the noise is often less noticeable or not there but i quite distinctive when i run on straight diesel.

    This will be caused by the different rates at which the 2 fuels burn. WVO taking just that little bit longer to ignite once squirted into the combustion chamber.
    Is your engine 'direct injection' or 'indirect injection'? Some people find that after running WVO for a period of time, they get some carbon build up on the injector nozzels. I would suggest as Tony says, have then serviced. Or at least move one and inspect it.

    I have heard of people connecting up a small tank direct to the IP and running several litres of Automatic Transmission Fluid through as an injector cleaner. This could be worth considering.

  10. #10
    Join Date
    Sep 2005
    Location
    WA
    Posts
    4,042

    Re: Piston Slap?

    Another option is to water fumigate the engine. With the air cleaner off and the engine at ~1KRPM or more, set the hose to give a fine mist of water and spray across the inlet. Allow the mist of water to be drawn into the engine (do NOT aim the hose into the inlet!!) Allow this to continue for 10 minutes or until water droplets come from the exhaust.

    Stop the hose, reconnect the air cleaner and go for a long drive (>30 minutes) to evaporate water from the exhaust system.
    I do this regularly (~2 month intervals) and it results in easier starting and smoother idling in my MB C250 Turbodiesel (on veggie oil).


    Regards,
    Tony
    Life is a journey, with problems to solve, lessons to learn, but most of all, experiences to enjoy.

    Current Vehicles in stable:
    '85 Mercedes Benz W123 300CD Turbodiesel single tank using 95% used cooking oil and 5% to 10% misfuel.
    '06 Musso Sports Crew Cab. Running on used cooking oil with 5% to 10% misfuel (where someone had filled diesel vehicle with petrol)
    Toyota Camry Hybrid - Wife's Car)

    Previous Vehicles:
    '90 Mazda Capella. (2000 - 2003) My first Fatmobile. Converted to fun on veggie oil with a 2 tank setup. Died when supercharger stuck at max boost for weeks. Stretched head bolts.
    '80 Mercedes 300D. 2 tank conversion [Sold]
    '84 Mercedes 300D. 2 tank conversion replaced engine with rebuilt OM617A turbodiesel engine. Finally had good power. Donor for current Fatmobile coupe.(body parted out and carcass sold for scrap.)
    '99 Mercedes W202 C250 Turbodiesel (my darling Wife's car) [sold]
    '98 Mercedes W202 C250 Turbodiesel (my car)[sold]



    Searching the Biofuels Forum using Google
    Adding images and/or documents to your posts


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