940 SE Turbo - oil consumption

Discussion in 'Volvo 940' started by Edward Milan, Jul 7, 2003.

  1. Edward Milan

    Edward Milan Guest


    10 year old - 157000 miles - goes like a bomb but using oil at 5 ltrs
    per 6000miles.(semi synthetic) Smoke from exhaust when under heavy
    acceleration in 3rd.

    No evidence of leaks, is it possible the valve stem seals are shot?
    and is there any way to check? I cannot think that it is the bores,
    performance is too good,

    Any suggestions would be most appreciated.

    Regards Jeff
    Edward Milan, Jul 7, 2003
  2. Edward Milan

    Tony Stanley Guest

    Mine does use oil too at about 2 litres every 6000, so needs topping up half
    way through service interval.

    I have several non Turbo B2xx engines before and inlet valve stem leakage is
    rare. I did do the head on my highest miler (200K miles) minor leakage at
    around 150K, but I did push the car hard. In comparison the Turbo drinks
    oil. If you think about it Turbos suck less on the seals so it should be
    less of a problem with air being pushed in.

    The most obvious sign of inlet valve leakage is blue smoke on start up.

    I think Turbo oil usage is quite common, by the sounds of it yours needs
    doing, mine probably not far behind.

    940 SE Turbo 2.3L, 1995, 110,000miles
    Tony Stanley, Jul 8, 2003
  3. Edward Milan

    Edward Milan Guest

    Many thanks for most helpfull comments.

    I should have said that tubo was replaced as a first option, but had
    no effect on oil consumption, however it was a second hand turbo so it
    could still be the cause. I still suspect the valve seals so will
    give it the test suggested.


    Regards Jeff
    Edward Milan, Jul 8, 2003
  4. Edward Milan

    volvowrench Guest

    by Edward Milan dropped his wrench, scratched his
    head and mumbled,
    Most turbo oil consumption is from crankcase pressure pushing oil up out
    of the oil separator and into the manifold. Once in the engine it is
    burned then the smoke cleaned by the convertor until the catalyst is
    coated. Make sure the PCV system is working correctly.

    volvowrench, Jul 8, 2003
  5. Edward Milan

    Tony Stanley Guest

    Been thinking about this for while now, but I can't understand the
    mechanism. Why should crank case pressure push oil out of the flame
    trap/oil seperator.

    On my car crankcase pressure is sucked into vacuum by a connection to the
    Turbo inlet side, as otherwise the connections would have to be pressure
    sealed. There does seem to be some terminaled device at the inconnect point
    which I don't know the purpose.
    There is also a diaphram device connected to the exhaust and inlet manifold
    (by metal pipes), and driven by a vacuum line with another electrical device
    in the air circuit to the manifold (ie it could be a pressure switch or
    sensor which controls this EGR thing). Haynes manual seems to be no help

    All the pipes were oily but not dripping.

    I'm familar with non-turbo simple cankcase ventilation on UK B200s (No
    EGR), but havn't grasped this turbo thing yet. What things go wrong with
    it, how is it likely to cause oil consumption?
    The non turbo just blocks up and blows out seals coating the engine bay with
    oil, or in some circumstance the small nipples block causing mixture
    problems as the air bypasses carbs and things.
    Tony Stanley, Jul 15, 2003
  6. Edward Milan

    Mike F Guest

    Oil vapour and fine liquid droplets get into the air in the crankcase,
    mostly through agitation by the moving parts. Extra "air" gets into the
    crankcase from blowby, and of course the higher the cylinder pressure,
    the more extra "air". This extra "air" has to leave through the PCV
    system, so more "air" then moves faster through the oil trap, giving it
    less time to remove the oil. If the system is not clean, then it
    doesn't work as designed, and the crankcase pressure goes up, and less
    oil is condensed out. This extra pressure also inhibits oil return from
    the turbo drain pipe, allowing extra consumption through the turbo
    bearing. And of course the extra pressure can get relieved through oil
    seals, in the mechanism you're familiar with.
    Mike F, Jul 16, 2003
  7. Edward Milan

    Mike F Guest

    To minimize oil consumption, keep the PCV clean. You may have to put in
    a new oil separator if the old one is too gummed up, because of the
    labyrinth design it's pretty hard to clean. However, it's not uncommon
    for those motors to use a bit of oil even when the PCV is in perfect
    shape, but this will minimize it.
    Mike F, Jul 17, 2003
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