engine oil in coolant tank

Discussion in 'Diesel Engines' started by CDK, Nov 19, 2013.

  1. CDK
    Joined: Aug 2007
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    CDK retired engineer

    The boat is going to stay in the water this winter, so once every few weeks I start the engines and let them run until the temp gauges are in the green.

    Last time I noticed the starboard engine temperature approaching the red zone. I lifted the floor panels to check the coolant level, but instead of greenish liquid there was only pitch black oil...
    These VW 1.9TD engines have an oil cooler sandwiched to the oil filter and are prime suspects, so I installed a new one although there seemed to be nothing wrong. I also flushed the cooling system, started the engine and noticed again a high temp and more oil surfacing. After switching off there was the typical sound of boiling water and some splashing from the coolant tank.

    Subsequently I removed the pump assembly, which is a very difficult job because it is located at the lower part of the engine, almost hidden by the alternator. But both the pump and the thermostat seem OK, although there was a lot of hard sediment I have no explanation for.

    The oil/water contamination can only come from a blown head gasket, but what may cause the high engine temperature? The engine never caused any problem since it was installed nearly 5 years ago and never did more than 3000 rpm.
     
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  2. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    A blown head gasket normally fails from the cylinder.
    If it connects to the water jacket the water will be heated rapidly, causing the boiling.

    I personally have never see oil in the coolant, normally I have seen water in the oil.

    That is a very simple statement of cause, so I am not sure it is going to be very useful. Most of the time things are less simple than I believe.

    Good luck when you pull the engine.
     
  3. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I have seen oil in the coolant. Do a leak down test, but I'll bet on the head gasket.
     
  4. gonzo
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    gonzo Senior Member

    What overheats the engine is the very hot exhaust gas mixing with the coolant. It will make it boil over.
     
  5. CDK
    Joined: Aug 2007
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    CDK retired engineer

    It is kind of a "the chicken or the egg" situation. No doubt about it that combustion gases can make water boil, but isn't it also true that overheating an engine causes the head gasket to fail?

    This engine has powered a VW Vanagon for more than 200.000 miles before it was marinized. The car was a service vehicle from a government institute car pool, well maintained, but many different drivers. As a boat engine it lead an easy life without abuse, so I do not understand what caused the gasket failure.

    I have not decided yet on how to proceed. Although the service manual says the head can be removed while the engine is in the vehicle I am not convinced it can be done in my boat due to lack of working space.
     
  6. michael pierzga
    Joined: Dec 2008
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    michael pierzga Senior Member

    Head gaskets blow when the engine overheats so its a possibility. Is your lube oil clean ? Is the pressure valve on the oil cooler filter assembly clean ?.

    Modern diesel engine heads are a bugger to remove.

    Double check your troubleshooting before you start busting knuckles and getting grease all over you.
     
  7. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    pressurise the cooling system to find the leak
     
  8. WestVanHan
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    WestVanHan Not a Senior Member

    I used to be in the car industry,and although the 1.9 is not notorious for blown head gaskets,it is known to happen a fair amount.

    IIRC the water pump's plastic impellers tend to break off and not pump well,leading to overheating.

    There are ways to test for exhaust gasses in the fluids as well.
     
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  9. CDK
    Joined: Aug 2007
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    CDK retired engineer

    I did expect to find only remnants of the impeller, but surprisingly there was no sign of damage.
    One possible cause for the blown gasket may be the turbo charger's wastegate that doesn't open anymore. The raw water injection near the base of the unit seems to have fused the steel shaft to the housing.
     
  10. WestVanHan
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    WestVanHan Not a Senior Member

    That just may be it.

    Hope that is it, and not a cracked head.
     
  11. Aliboy
    Joined: May 2011
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    Aliboy Junior Member

    Seized wastegate, variable vanes not operating, all causes of failures in modern marine diesels. Was talking yesterday to a person who had recently blown their marinised 3.0l Toyota diesel due to a seized wastegate. If all it has done to yours is blown a head gasket that would be a happy result. Often an easy check for a blown head gasket is to warm up the engine with the coolant tank cap off and then check for bubbles in the coolant once the thermostat opens. As a side note, I have a friend that recently found oil in his coolant on an old 120hp Ford. Haven't tracked it down yet, but so far most likely scenario is a blown head gasket.
     
  12. Adler
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    Adler Senior Member

    Control

    Have you checked the tighting torque to the cylinder's head screws ?
    Many times on marinized vehicles' engines observed lower tension to cylinders' heads
    screws as an effect to continious vibration conditions in marine use.
    I think you have to try check the torque level of these screws by a torque-key
    to compare if that admitt the VW requirements.
     
  13. CDK
    Joined: Aug 2007
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    CDK retired engineer

    I wish it was that easy!

    To even see the bolt heads (Torx!) the #1 piston must be in tdc position, the timing belt removed, the upper pulley, then the camshaft.
    And there is no torque to be checked, because after tightening each bolt is turned another 270 degrees. These are called stretch bolts, they can be used only once.
    I am about to do all that and more, because the gaskets come in 3 different thicknesses and must be ordered in Germany.
    So far the weather has worked against me: two hurricane strength storms straight into the bay. Various parts and tools have fallen in oily soup in the bilge, I wasn't prepared for such waves.
     
  14. powerabout
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    powerabout Senior Member

    ah the joy of modern engines..
     

  15. Redtick
    Joined: Jul 2009
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    Redtick Junior Member

    Another joy of modern engines, having worked on over the road trucks with high mileage.
    Another source, Electrolysis opens a oil passage into cooling system.
     
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