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bluish white smoke from tailpipe - '06 4.8 vortec

Discussion in 'Chevy/GMC 4x4' started by depraved, Jun 16, 2012.


  1. depraved

    depraved
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    My brother-in-law and myself are trying to determine whats causing his '06 silverado 4.8 to blow bluish/white smoke out the tailpipe when driving.

    A little background...

    we've done a few oil changes in the last couple of weeks and after the oil change, the dipstick shows full and a few days later, the truck all of a sudden starts to blow smoke out the tail pipe while driving. Re-checking the oil level comes back with a dry dipstick. Oil pressure the whole time is being displayed via the dash as having 40 pounds of pressure.

    We ripped off the intake this morning to find that it was full of oil. We had a thought that it might not be correctly draining and pulled the lifter valley cover off to find no excessive oil in the top of the block.

    Apparently, there is no PCV valve in this motor, so replacing that is out of the question.

    truck has approximately 200,000 miles on it also.

    Anyone run into this or have any ideas on where to look next? We're concerned that the dipstick showing dry even though the dash is reporting good oil pressure may cause long term problems for the motor.
    More importantly, how is the oil getting into the intake with enough volume to cause this smoking?
     

  2. JasonB

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    my guess, head gasket letting oil in chamber and what is not burning is getting pulled by the EGR into the intake
     

  3. Tango

    Tango
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    Sounds like the intake gasket is bad.

    When the engine gets low on oil, the oil preasure goes up. It's not a volumn meter, it's a preasure meter. It's still pickin up oil even though it's below the dip stick level.
     
  4. depraved

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    When we pulled the intake off, we didn't see any signs of oil around the intake ports on the head; the gasket "appears" to not have been leaking.

    We'll look into this a little more.
     
  5. JasonB

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    have you checked the compression? you could be blowing oil past the rings, then like bad head gasket sucking oil through the egr into the intake
     
  6. depraved

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    We haven't checked compression yet but upon further investigation, it looks like the intake gasket around one cylinder had a bit more oil then the others and the spark plug for that cylinder was in worse shape then the others.

    We've got it put back together now (can't do a compression test without it together) with a new intake gasket and we'll see how we do.

    Thanks for the responses; crossing fingers that the new intake gasket fixes the issue.
     
  7. Heiseroil

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    I would do a compression test just to be sure it's not blowing past the rings, but it sounds as thought you may have the problem solved :D
    Scott
     
  8. Tango

    Tango
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    Another way for oil to get in there is intake valve guides leaking, but the intake gasket is the most likely issue.
     
  9. depraved

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    update.....

    We replaced the intake gaskets and unfortunately, driving the truck down the street, smoke started to blow out the tailpipe.... grr!

    Compression test results in numbers between 175-200 across all 8 cylinders.

    We bought an new "updated" valve cover that is "supposed" to resolve some of the issues with the original valve covers but we don't want to put it on unless we know for sure it will fix the issue.

    Any other ideas on where to look next before going down the road of replacing the valve cover?

    Thanks everyone!
     
  10. Tango

    Tango
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    How does the engine breath .. and where does the oil vapor go without a PCV valve?

    Do you have any other lines that could vacume the oil into the intake?

    I think bad intake valve guide seals could also cause that and is likely with 200k on it.
     
  11. depraved

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    There is the brake booster hose and one other that attaches near the throttle body. any easy test to determine if its valve guide seals?
     
  12. depraved

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    Problem solved! Replaced the drivers side valve cover and the issue is now gone!

    Thanks for everyone's thoughts on this.
     
  13. Tango

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    Glad you fixed it


    How does a new valve cover stop engine oil from entering the intake manifold?
     
  14. depraved

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    According to Chevy, the "PCV valveless" valve cover underwent a design change when they started to see excessive oil blow-by.

    I don't have any pictures, but looking at the two covers, you can see slight differences in the channel that vents out of the cover.
     

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