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Blue Smoke on Startup 320 CDI 2001

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by Frontstep, May 18, 2020.

  1. Frontstep

    Frontstep Senior Member

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    Your Mercedes:
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    Could someone fill in some more alternative things for me to look at I know there's a few but I am sure I have missed something.

    The car smokes a lot on startup only not over-run, its bluey grey and points to oil with no smell of diesel.

    Its had injectors full recon set, oil separator,glow plugs and module etc

    Starts straight away within seconds and a bit lumpy but clears, then runs well.
     
  2. LostKiwi

    LostKiwi Senior Member

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    Have you checked for movement on the turbo spindle?
     
  3. EmilysDad

    EmilysDad Senior Member

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    blue smoke on start up is usually/often a sign of worn valve stem seals .... oil leaks passed the valve seals, generally over night, into the bore hence the smoke on start up.
     
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  4. malcolm210

    malcolm210 Senior Member

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    My petrol M103 was bad for valve seals and smoking on start-up
     
  5. OP
    Frontstep

    Frontstep Senior Member

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    Thanks the valve stem oil seal suggestion I thought I had dealt with by the "over-run" observation.

    As I understand it oil is sucked down past the seals and into the combustion chambers.

    You then put your foot down and "open the throttle" then small amount of oil is then instantly burnt with the fuel/air mixture giving you the quick puff of blue smoke.

    The turbo bearing play I can't to be honest get my head round,

    why only on startup ?
     
  6. LostKiwi

    LostKiwi Senior Member

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    When running any small amount of oil coming past the seals is picked up and burnt with a large volume of air. When you shutdown any oil in the inlet tract from a bad seal can pool at the lowest point, such as a valve or cylinder (if a valve is open). When you restart the pooled oil gets drawn through and gives blue smoke.
    If a seal is only seeping manifold pressure from boost will also push against any seep, but at idle/startup that pressure isn't there.
     
    Frontstep and abazem like this.
  7. abazem

    abazem Senior Member

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    So would it be a good idea to put car on idle for 2-3 minutes before shutdown?
     
  8. OP
    Frontstep

    Frontstep Senior Member

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    So an inspection of my pipe work and Turbo seems in order, thank you,

    surprisingly I have a lot to do, I have taken on some covid projects as I call them.
     
  9. LostKiwi

    LostKiwi Senior Member

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    One minute is sufficient to maintain turbo health after a hard drive.
    If it smokes then investigation is required to see if the seals are leaking.
    Simply idling for 2 minutes won't fix it, just hides the symptom.
     
  10. sheryllee

    sheryllee Member

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    The common cause of blue exhaust smoke is oil leaking past engine seals and into the cylinders
     
  11. OP
    Frontstep

    Frontstep Senior Member

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    The Turbo has finally been changed and the smoke already a lot better thanks for the pointers.

    The car needs a throat-clearing run to burn out the oil.
     

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