coolant dripping from blowby tube

Discussion in 'Trucks [ Eighteen Wheelers ]' started by rank, Jun 10, 2014.

  1. rank

    rank Road Train Member

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    50 miles north of Rochester, NY
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    1986 Peterbilt model 359. 3406B Cat.

    I noticed a little puddle of coolant under the truck. Started it up and watched. Drip...........Drip.........drip. Coming from the blow by tube or PCV tube that is connected to the top of the rear rocker cover. How can this happen?

    Head gasket leaking, turning to vapor and condensing in the blow by tube as it cools?
     
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  3. rollin coal

    rollin coal Road Train Member

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    Could be that or cracked liner. When mine started doing this almost a couple of years ago I had it inframed. Curious if you were sampling regularly? I wasn't at the time so it was a not so nice little surprise. Not likely that sampling would have prevented anything but it probably wouldn't have been such a kick in the nads had I known a little ahead of time there was an issue. Or probably I would have stressed about it who knows. I never saw any coolant in the oil until I noticed it dripping out the blowby and blowing tell tale steam. Then it got worser and worser until i got it home 300 miles later.
     
  4. GrapeApe

    GrapeApe Road Train Member

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    Could be a few things. Are you getting any oil in the radiator? That could be an oil cooler. The water pump could be leaking into the crank case, which is usually with a cold water leak at the weep hole. After that it gets expensive, head gasket or liner problem. How much coolant is it using?
     
  5. BeenJammin

    BeenJammin Light Load Member

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    Sounds like overhaul time, liner oring or perforated liner problem down low. Drop your pan and take a look around the base of your liners to see for sure.
     
    wore out Thanks this.
  6. special-k

    special-k Road Train Member

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    Doesn't sound good. See if it's pressursizing the rad also. Then pull a valve covers or the one the hose comes from and see how much condensation is in their. If your on the road loosen the rad cap and keep it topped up with water and nurse it home. I wouldn't shut it off more than I have to incase it's going into the barrels. Check the oil to see how bad it looks too. Good luck and hope it's something simple.
     
  7. wore out

    wore out Numbered Classic

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    CHASIN THE DEVIL'S HERD
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    Hopefully its just a water pump or oil cooler issue. I always pull the pan like Been Jammin said and pump up the radiator. Shows the leak for sure every time.
     
    BeenJammin Thanks this.
  8. maggard359

    maggard359 Medium Load Member

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    Could it be running down blowby tube and not actually coming out of it? My b models all had seeped at back of head as a cold water leak with age. Pull oil filler cap you should find it to be milky if indeed you have oil and coolant mixed.
     
  9. BeenJammin

    BeenJammin Light Load Member

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    I forgot about another place to check. Make sure the nozzle adapters that the nozzles go into, aren't leaking coolant back up into head. They thread in and have an oring seal at the top of the coolant passage to seal on the upper side. Seen a few of them leak, but not very often.
     
  10. pupeperson

    pupeperson Light Load Member

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    Another possibility could be the air compressor.
     
  11. rank

    rank Road Train Member

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    50 miles north of Rochester, NY
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    Thanks for the replies. Just bought the truck. I have only put ~7,500 miles on it. Recent inframe , new head, nozzles. Coolant level was down a gallon. Oil is not milky. It does seem to burn some oil....level on dipstick is falling. Faint smell of coolant in can when I turn A/C on.

    At first I did think it was running down the outside of the tube, but then I chaunged my mind. interesting you say that. I will look again. Very slow drip so it's hard to tell.
     
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