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A different slant on oil-coolant leak

John_Tuohy Apr 18, 2014

  1. John_Tuohy

    John_Tuohy New Member

    AUDI A4 1.9 TDI

    This one comes down to No pints for a month vs No pints for a year.

    I originally had a coolant leak through a tear in what looks like an emergency pressure release. It is a mushroom-shaped hollow rubber knob on the passenger side of the engine. The mechanic replaced that along with an oil/filter change.

    The following day, the coolant level had dropped again. I thought, ok just topping up from trapped air and thought nothing of it.

    This morning, the engine wouldnt turn. Eliminating the battery, I checked the oil and found a grey oil/water emulsion.

    The easy conclusion is that the head gasket is gone.
    However, the engine had never gone above 60 deg C while the coolant was leaking, the oil was black before it went into the garage and there is no blue in the exhaust so I am wondering if it is possible to feck up the oil cooler whilst changing the oil filter ?
    Last edited: Apr 18, 2014
  2. AlexGSi2000

    AlexGSi2000 Well-Known Member VCDS Map User

    Have you got any further with this?

    I would personally say that the oil cooler would be a good place to start.
  3. John_Tuohy

    John_Tuohy New Member


    Thanks Alex. I'm wondering how the mechanic can distinguish between the two.

    BTW it was Easter weekend so the car is still sitting at home waiting for the mechanic to pick it up.

    Here is the sequence of events that has me wondering if the mechanic missed the original issue:
    (1) The coolant level was dropping because the rubber mushroom was ruptured.
    (2) There was no water in the oil before the repair because the oil was black before the car went into the garage
    (3) I assume the rubber mushroom is an emergency pressure release / bursting disk. The question is what caused it to burst.
    a. Overheating? There was no steam release and the thermometer never exceeded 60 deg C. The diagnostics may show more sensor results and clarify the picture.
    b. There was back pressure due to a constricted line. The mechanic replaced the mushroom with a bit of hosing closed at the end. Would the weakest link would now be the head gasket ?
    c. Did the mechanic disrupt the oil cooler when or would the weakest link actually be the gasket in the oil cooler or was the original constriction in the oil cooler?

    Any thoughts ?

    bearings/rust/bearings/rust.................. [​IMG]
    Last edited: Apr 22, 2014

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