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Crankcase pressure? 700

posted by  dlot on  Fri Feb 21 04:42 CST 2003
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last visit: Sat Nov 17 13:53 CST 2001
[RELATED]

Hi,
I have a friend with a 1988 760T. The motor runs well. He had some issues with
the dipstick blowing out of the tube. So I had him get the breather box
and the PCV system cleaned. Now this still happens. The car has about 150k miles
on the motor. My question is how does the PCV work on the 760Ti motor? The
reason I ask is because the small hose that runs to the fitting on the intake
manifold from the plastic three way connector doesn't block any boost
pressure. Isn't there supposed to be a check valve or something in this hose?
It would appear that when the motor makes boost pressure it can pressurize the
crankcase through this hose. Or does the pressurized air just get diverted to the intake air pipe? I'm willing to believe that his motor just has too much blowby but I want to be sure before we convict it and say it's a bad motor. Are there any other ways that the crankcase could be pressurized and cause this type of problem with the dipstick blowing out? Thank you for all you help
everyone.

Dave 82 242ti 280k mi.








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    Crankcase pressure? 700

    posted by  the kick inside on  Sat Feb 22 01:12 CST 2003
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    last visit: Thu May 17 09:58 CST 2007
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    i had issue on my 940t and that big pipe accross the cam was the issue, it may look big and be clear (i could run degreaser thru mine easily, but mine had coked up enough to not be breathing right...I spent an hour with a piece a plastic coated wire and degreaser (made the hose into a U shape, filled it ran the wire through it, emptied - refilled repeated) and was amazed at (a) the amount of hard rud that came out and (b) the difference it made!

    just a thought - also it doesnt have a flame trap installed does it - cos i believe it shouldnt have! (i.e. fitting is there but mesh isnt!)







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      Crankcase pressure? 700

      posted by  dlot on  Sat Feb 22 05:31 CST 2003
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      last visit: Sat Nov 17 13:53 CST 2001
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      Hi,
      That's my next suggestion for my friend to try. Thank you for the help.
      I'm pretty sure that there is some part of the system that just isn't
      kosher.

      Dave 82 242ti 280kmi.








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    Crankcase pressure? 700

    posted by  Aye Roll on  Fri Feb 21 10:22 CST 2003
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    last visit: Tue Oct 14 21:08 CST 2014
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    A compression test or better yet a leakdown test will verify what the real problem is. It could just be plugged PCV stuff. It could be as bad as a burnt piston. Short of tearing it all down, the leakdown is the best check. It'll find any leak past either rings or valves.
    --
    Rob Bareiss, New London CT ::: 86 244DL, 87 244DL, 88 744GLE, 91 244: 808K total








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      Thanks for the replies! 700

      posted by  dlot on  Fri Feb 21 13:34 CST 2003
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      last visit: Sat Nov 17 13:53 CST 2001
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      Hi Rob,
      Thank you for the reply. We had his breather box and PCV stuff cleaned out.
      I'm going to double check it when I get a chance. I'm with you on the
      tests but I don't know if I'll be able to get him to my place where I can
      do a compression and leakdown test.

      Thank you every one for the assistance! Happy rolling!

      Dave 82 242ti 280k mi.








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    Crankcase pressure? 700

    posted by  VolvoSteel on  Fri Feb 21 07:38 CST 2003
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    last visit: Sun Mar 23 21:28 CST 2014
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    The crankcase ventalation is listerlly pulled right out of the engine on a turbo and then sent right back in and out the exhust, as long as the turbo works right it will pull the pressure out and have it recombust in the chamber and out the exhust and that is done for every fire, now if you think you have a bad motor hence "Rings" you should see white smoke comming from the dipstick area as volvo's tend to let that smoke through normally with good rings youll notice it, check for oil in the pipe which comes accross the top of the valve cover for excessive oil, thats the one which lets the engine breath the legal way. good luck. also keep in mind there is no Brather box or Flame trap on some early turbo models and even later on there still wasnt flame traps this only applies to the turbo models.








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    Crankcase pressure? 700

    posted by  dick on  Fri Feb 21 05:20 CST 2003
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    last visit: Sun Aug 3 15:24 CST 2014
    [RELATED]

    Check that the dipstick O ring is good. Have heard of this being a problem at times. The vent system on a turbo does not use a flame trap and all fumes from the crankcase should be diverted as you suggest.

    dick








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      Crankcase pressure? 700

      posted by  dlot on  Fri Feb 21 06:00 CST 2003
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      last visit: Sat Nov 17 13:53 CST 2001
      [RELATED]

      Thank you for the replies guys! I will have him check the O ring. I'll also have him make sure the big hose from the three way connector to the intake pipe isn't clogged. I guess after that I have to blame the motor itself.

      Any boosted air that gets into those hoses is supposed to be sucked into the intake. Now I understand how it works. I wonder if this is better enough to
      use this setup on a 240? Happy rolling!

      Dave 82 242ti 280k mi.







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