Excessive crank case pressure

Discussion in '70-Series Tech' started by divemedic, Sep 14, 2018.

  1. divemedic

    divemedic

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    1PZ, 90* sitting at a light on a slight hill. Idle gets really rough truck almost dies. I feathered the throttle to keep it alive. Light turns green. Truck dies in the intersection. Try to start, fires on forth attempt. Drive into the grass off the road and shut it down. Gauges all real normal. Open the hood. Couldn’t unscrew the oil cap. Weird. Pull the dip stick and blasted by oil. I let it rest a few minutes. No oil on dip stick. Residual oil is black, no signs of mixing. No puddles. No other notable symptoms.

    D51A6B17-A13B-4182-BC9C-AE033F16EEC9.jpeg
     
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  2. GreaseMonkeyJP

    GreaseMonkeyJP

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    Was it running when you pulled the dip stick?

    If not the crankcase vent is definitely very clogged.
    Not sure how this would cause a rough idle on a diesel thought.
     
  3. divemedic

    divemedic

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    Not running. The rough idle started immediately before the shut down.
     
  4. roscoFJ73

    roscoFJ73

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    It needs to be compression tested. Something has caused a massive leakage past the rings. Im not sure if oil pressure could do this and it would have shown on the gauge. Whats the mileage and general condition of the engine?
     
  5. divemedic

    divemedic

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    230k km and generally in good shape. I’ll call around for a shop willing to touch the truck.
     
  6. GreaseMonkeyJP

    GreaseMonkeyJP

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    After it was restarted was it still running very rough, or did it clear out when you were pulling into the grass?
     
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  7. divemedic

    divemedic

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    Cleared up. Ran fine on the drive home (about 2 Miles)
     
  8. roscoFJ73

    roscoFJ73

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    Very odd for it to do that then come good. Is it still getting pressure build up?
     
  9. GreaseMonkeyJP

    GreaseMonkeyJP

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    I think that the crankcase pressure is because of the vent being clogged. Even a perfect engine will have some blowby into the crank case, and on the 1PZ, 1HZ family the vacuum pump also pushes additional air into the crankcase. So given that it maintained pressure while off tells me that the pressure had no where to go.

    This condition may also be made worse by a vacuum leak causing the vacuum pump to pump more air into the crankcase. (This or a clogged air filter would cause extra flow through the vent leading to it clogging)

    Was the AC on when this started? If so I would look at the vacuum hoses as a vacuum leak could have kept the idle up from functioning when the AC compressor went on which would cause a rough idle.

    A pressurized crankcase will also cause oil to leak out of an otherwise leak free engine. Which could be the cause of your low oil level.
     
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  10. divemedic

    divemedic

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    AC was on I will look into this for sure. I am also looking for someone to do a compression test as well.
     
  11. divemedic

    divemedic

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    So I’m fairly certain I figured it out. I had a DIY catch can on, I think the heater hose I used was the culprit. It had become linked on a bend. I replaced the whole thing with an emissions tube for a ford. I’ll be calling Ward Harris soon for a propper catch can.
     
  12. AirheadNut

    AirheadNut

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    I had something similar happen, but my dipstick blew out while I was driving and I lost about a quart of oil into the engine bay. Does your dipstick have something that holds it in?
     
  13. divemedic

    divemedic

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    Nothing other than standard equipment.
     
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