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Thread: Defective PCV Oil Trap made screeching sound

  1. #1
    Join Date
    Aug 2017
    Location
    Pleasanton CA USA
    Posts
    308

    Default Defective PCV Oil Trap made screeching sound

    I'm posting the problem and RESOLUTION here. The correct title will make it more searchable.

    The problem arose as a hi-pitched screech or chirp sound coming from the engine after warm-up, and whenever the RPM got up to 1300-2000.
    It sounded so much like a failing belt idler roller-bearing, the natural impulse was to grab a stethoscope....all the pros who looked at it fell for that theory.

    This "chirp" was a ruptured membrane inside the PCV oil trap (long black box covering valves, top of engine near windshield). No wonder it couldn't be located with a stethoscope! More typically, the sound is a steady whistle. In any event, to diagnose it, you merely remove the oil filler cap and the sound silences in response.

    This is a simple repair anyone can do. You have to replace the PCV oil trap and gasket ($170).

    Click image for larger version. 

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  2. #2
    Join Date
    Jul 2018
    Location
    Kansas City
    Posts
    7

    Default

    I believe there is a TSB or some directive from Volvo on the matter. But I think you have to complain about it to get them to act.

    My local dealer did this replacement free of charge.

  3. #3
    Join Date
    Aug 2017
    Location
    Pleasanton CA USA
    Posts
    308

    Default

    Can anyone speak to the normal function of this oil trap, and the critical role of the plastic membrane? What impact of driving with a ruptured membrane?
    I found one reviewer on FCPEuro saying that it regulates the negative crankcase pressure to about -1.7 psi, and that when it ruptures there is a loss of regulation creating a severe vacuum (- 7.0 psi). What impact on oil seals? Lowering of engine oil pressure?

    Also, does the rupture of the oil trap membrane warrant doing an oil change? Isn't the trap supposed to separate out water vapor and combustion gasses so they don't get mixed into oil draining down to the sump?

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