Blown turbo symptoms?

Discussion in 'Z32 Technical' started by Cliff, Feb 12, 2019 at 2:45 AM.

  1. Cliff

    Cliff Member

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    My car is producing blue smoke from the exhaust under these conditions; either:

    1. Once the accelerator is touched after engine braking (coasting without using the clutch or neutral).

    2. On extreme engine braking (as if preparing to come to a complete stop).

    Here is a video that shows me coasting and then using the throttle. The end of the video shows me hard engine braking (2nd gear) and the effects of such.



    It only happens under vacuum (-12psi or stronger) and not really when boosting.

    Only a small amount of smoke on startup (forged pistons in 30° F weather), but goes away once engine is at temperature.

    No smoke at stop lights (unless engine braking is used). Throwing the car in neutral before slowing down prevents smoking.

    My searching around most point to blown turbo seals or leaky valve stem seals. But I just replaced the valve stem seals 6 months ago.

    So here are my questions:

    In any case (valve seals or turbo seals) how likely is it for both sides to start smoking at the same time (granted the right side is considerably worse)?

    If it were turbo seals, wouldn't I see oil dropping from the turbos? Mine are dry.

    Screenshot_20190211-104116_Gallery.jpg Screenshot_20190211-104132_Gallery.jpg

    If it were turbo seals, wouldn't there be oil in my intercoolers? Mine are dry.

    If it were the valve seals, wouldnt that affect my compression numbers? Mine are the same as they were 6 months ago; cylinder:

    1. 145
    2. 140
    3. 140
    4. 140
    5. 142
    6. 140

    The thing that really throws me off is that this all started happening after I changed and bled my brakes :eek:o_O

    Any insights as the what and where to start looking or diagnosing are greatly appreciated :(
     
  2. beaver

    beaver southern zeds

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    Check the inlet side pipes of the intercoolers, that is where you'll find oil if a turbo seal is leaking oil into the compressor side of things, the other intercoolers pipes usually only have a light film of oil showing. Valve stem seals usually leak oil into the chambers after the car has been shut down over night and smoke at start up next day, then is gone until the cycle is repetted. Is the engine oil level right?
     
  3. Cliff

    Cliff Member

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    The oil level has been dropping lately. I checked the turbo / intercooler / piping thoroughly and there was no oil at all. I'm much more optimistic about the cost of this repair now.

    This article pretty much sums up exactly what my car has been doing. I guess it is the valve seals. I'll replace them and see if that fixes the smoking.

    https://itstillruns.com/bad-valve-seals-symptoms-7448959.html
     
  4. beaver

    beaver southern zeds

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    If you know how to use a vaccum gauge as a diagnostic tool/guide, use one before you start dismantling the engine. The reading should be easy to interpret, stem seals are gone after only 6 monthso_O, it also possible the guides are out of spec. On deceleration where does the needle on the factory boost gauge sit?
     
  5. Fists

    Fists Well-Known Member

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    That's actually unusual, what's your cam breather/PCV set up?
     
  6. Cliff

    Cliff Member

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    Well I dont have the factory boost gauge hooked up anymore. Instead I have a Haltech CAN gauge which on deceleration pulls anywhere from -14/15psi to -10psi (car is tuned via VE, no MAF sensor). I'll see if I can find some tools to do a leak down test today.

    My PCV system is setup with two oil catch cans so that the crankcase is sealed other than the intake valve cover breather vents. Both PCV valves on the plenum are plugged. Both PCV vents on the left side exhaust valve cover are plugged. Both PCV vents on intake valve covers vent to oil catch can and then atmosphere (legal where I live). Both intake pipes plugged where PCV joins. I made this change because I was popping the oil dipstick out under higher boost 15-18psi.
     
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  7. Cliff

    Cliff Member

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    So I had a theory.

    If the intake valve cover vent and hose become clogged, would that nasty stuff get sucked back into the valves under vacuum?

    Well, the tubes to the catch can seem fairly clear so maybe not.

    Screenshot_20190212-073223_Gallery.jpg
     
  8. Cliff

    Cliff Member

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    Through the spark plug holes I can see shiny (assuming wet) oil on the pistons. Another vote for the valve stem seals.
     
  9. Cliff

    Cliff Member

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    Another thought, I had to replace the intake valves on the right hand side and I lapped them in by hand. Do you think a bad valve seat would still show good compression?

    The most confusing part here is how out of the blue this issue started. Yes I replaced 6 valves and seals on the right hand side of the engine but Ive had zero issues for nearly 5,000 miles. So why would smoke show up like this out of nowhere and from both banks as well?

    Does excessive boost affect the valves in anyway? I only boosted to 21psi a few brief times never holding that pressure for more than a second.
     
  10. East Coast Z

    East Coast Z Well-Known Member

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    Blue smoke indicates burning oil.
    Blue smoke on a trailing throttle (decelerating) indicates leaking valve stem seals.
    Blue smoke on power (accelerating) indicates worn or damaged piston rings.

    Think about it...........
    If the turbo seals are gone, the oil can only enter the combustion chamber via the inlet manifold, as it would be carried over with the air.
    If the throttles & induction hoses aren't contaminated with oil, chances are it isn't the turbo's.

    Leaking valve stem seals won't affect compression figures because the valve stems aren't exposed to the combustion chamber when the valves are closed.
     
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  11. Martin Williams

    Martin Williams Active Member

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    I know this sounds silly, you said you lapped in valves your self. you didn't lap them in with valve seals fitted did you and you did do an ultrasonic head wash afterwards. Any ANY grinding compound residue left on valves, valve guides or valve seals will very quickly damage all of these. Just a thought!
     
  12. Bob Lloyd-Jones

    Bob Lloyd-Jones Oldreverbob

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    A test for youValve guides & valve seals worn cause oil smoke when pulling a vacuum on a down hill run with throttles closed.
     
  13. Cliff

    Cliff Member

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    Martin: I didnt lap the valve with the seals installed lol. But you do worry me with having the head dipped and cleaned afterwards. I cleaned up each valve and port with brake cleaner on a cloth, IIRC.

    I've got a buddy coming over this weekend to hopefully get this fixed in a 24 hour turnaround. I'll take some pics and let everyone know what we find ;)
     

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