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Thread: blue smoke

  
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    Scrappy Doo's Avatar
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    blue smoke

    Has anyone experienced any blue smoke coming out of the back of there car?

    My is really random, when the car is warm, I'll be driving down the road and I'll look out of the rear view mirror and see a big cloud of smoke kinda bluey looking, then it'll be okay for a good while then again a good while later it'll puff again.

    It's not a constant stream and it's a bit random..... anyone had this problem? does it sound like the Turbo letting go?
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    blue smoke out of the exhaust is usually burning oil mate
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    When does the smoke appear - on lift over, full throttle, randomly, just drving along, only when the engine is warm...?

    Let us know as it will be easier to make a guess as to what it is.

    Also, how many miles has the car done?
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    The car has covered 34K miles, the smoke appears on throttle most of the time, but I dont have to be ragging it for the smoke to happen, just cruising aswell it does the same, and only when the engine is warm and at low speeds, can't really see it doing it when I'm cruising at 70Mph!
    "Real cars don't come with free insurance."

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    BenC's Avatar
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    sounds like the turbo oil seal, one tiny drip of oil can make a hell of allot of smoke... so perhaps its just squeezing through randomly?
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    Was thinking that it's the seals on the turbo slowly letting go, can these be replaced easily? or is it a recon / new turbo job?
    "Real cars don't come with free insurance."

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    Oh forgot to add, the oil level in the car is going down. Vauxhall had it for a engine management fault, they put the smoke down to the over fueling, but now the fault is fixed it's happening!!
    Would an over fuelling / wrongly fuelling car cause the oil seals in the turbo to weaken?
    "Real cars don't come with free insurance."

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    Turbo Oil seal appears to have a probelm then - get VX to deal with it pronto - before it becomes VERY VERY serious.

    if the fuel gets in contact with certain materials then it could cause corrosion of components so it is plausable that the overfueling could be a contributing factor.
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    is it expensive to replace the turbo seal?
    "Real cars don't come with free insurance."

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    got this off max-boost website
    although this is generally c20let site

    White/blue exhaust smoke - help!

    This is a common issue, and most people are quick to jump into the conclusion that the turbo needs reconditioning. Hold your horses, this is not necessarily the case!

    There are four possibilities here

    The engine is producing the smoke
    The engine is forcing the turbo to produce smoke
    The turbo is smoking
    All of the above
    1. The engine is producing the smoke

    Valve stem seals on older engines can allow excess oil to enter the combustion chambers. This will manifest itself as exhaust smoke (smelling of burnt oil) during idle and deceleration mainly, but in reality the smoking will be constant. These symptoms are quite similar to those of a turbo bearing being out of spec. Changing these seals means taking the cylinder head off and dismantling the valves - not a bad thing to do on a high-mileage engine, anyway.

    The piston rings could also be tired and loose, letting excessive 'blowby' go through the rings, pressurising the sump and getting out via the crankcase ventilation (thick pipe next to oil dipstick -> camcover sealed passages -> thick pipe at back of camcover -> turbo intake). This can be 'rectified' (read:: botched) by blocking off the small intake pipe at the turbo end, and venting the camcover pipe to the atmosphere via a small airfilter, and/or an oil catch tank. These blowby gases are poisonous and corrosive, so we don't want to breathe them if we can avoid it!

    A compression test can show if the rings are in need of refurbishment. Even if the figures are within the acceptable range, the rate of pressure build-up is a good indicator. While cranking the engine, fresh rings will show (say) 165-170-175-175-175psi. Tired rings would go like 155-165-167-169-170-171, building up pressure for several crank revolutions. A dry/wet test would also show a couple of bar increase during the wet cycle.

    Even better, a leak-down test will show even more precisely if your rings are done. Local copy here.

    Here's how to make a leakdown tester for minimum money

    2. The engine is forcing the turbo to produce smoke

    Blocked breather pipes would fall into this category. They could be full of oily and sticky residues becoming effectively blocked, or kinked. This would lead to the sump becoming pressurised, creating pressure that would not allow the turbo oil return to flow (it's gravity-run, remember, as opposed to the turbo oil-feed that's pressurised). Therefore fresh oil would be piling up through the oil feed, but with no easy exit, the oil will have to push itself back through the turbo seals finding itself both into the intake charge and directly to the exhaust gases. Fixing this blockage would correct the problem immediately.

    For idle and very low throttle openings, the LET also has a smaller breather hose from the camcover to the bottom of the inlet manifold - via a flimsy one-way valve. This valve ensures that under boost the camcover isn't pressurised. It only helps suck out the crank fumes while off-boost.

    3. The turbo is smoking

    That's when the clearances within the turbo are out of spec and oil leaks through the seals whenever there is pressure differential. High-flow exhausts exacerbate this problem, as of course running high boost pressures.

    There is this theory that 'thin' oil leaks through the seals while 'thick' oil doesn't. Conventional wisdom would support this argument, but I have seen no evidence whatsoever to back it up, despite changing from the thinnest of oils (synthetic 0w40) to the thicker ones (15w50).

    4. All of the above

    In real life, older engines would tend to suffer from all of the above, especially if they haven't been reconditioned in the past. So the head would be full of carbon deposits, the stem seals leaking, the turbo seals past their prime, and piston ring blowby on the high side. Trying to pinpoint the 'blue smoke' to just one factor can often be futile, as there are several contributors, and even fixing one of the causes would still leave the car smoking.
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