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Burning oil...

Discussion in 'The Garage' started by BlackDog714, Nov 10, 2003.

  1. BlackDog714

    BlackDog714 1/2 ton status

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    A friends truck started burning oil recently. It's a 84 K5 /forums/images/graemlins/k5.gif with a 305. What seems wierd to me is that it doesnt smoke at start up. It starts, runs and idles fine, then after 5 min or so, it starts to smoke REAL bad. Another mechanic friend of his (Bubba Joe Mechanic, not a real mechanic) said it was probably the vacuum modulator on the 700R????

    Does this make any sense? I would think rings and valve seals would smoke at start up too.

    Thank you for your opinions...
     
  2. khotmer

    khotmer 1/2 ton status

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    Is the oil level go down ? if not check the tranny fluid level...
     
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    You can rule out the tranny. 700r4s don't use a vacuum modulator.
     
  4. khotmer

    khotmer 1/2 ton status

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    guess i should read entire sentences...
     
  5. k5guyva

    k5guyva 1/2 ton status

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    My guess is that something leaks when the engine gets warm. That means thermal expansion. I would start looking at the head gasket. Retorque the head bolts and make sure nothing is loose.

    Does it burn oil? Is there any in the water from the radiator? Is there water on the dipstick from the oil? How much oil do you have to add?
     
  6. BlazerWheels

    BlazerWheels 1/2 ton status

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    [ QUOTE ]
    Is there any in the water from the radiator?

    [/ QUOTE ]

    Don't mean to hijack...but what does it mean if there is oil(or something) in the coolant resevoir??? /forums/images/graemlins/confused.gif
     
  7. BobK

    BobK 1/2 ton status

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    Bad head gasket
     
  8. BlazerWheels

    BlazerWheels 1/2 ton status

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    Would this also be the reason for the mysterious loss of coolant without any visible puddling or wetness??? /forums/images/graemlins/confused.gif
     
  9. clubba68

    clubba68 1/2 ton status

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  10. k5guyva

    k5guyva 1/2 ton status

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    [ QUOTE ]
    Would this also be the reason for the mysterious loss of coolant without any visible puddling or wetness??? /forums/images/graemlins/confused.gif

    [/ QUOTE ]

    Probably. You have to ask your self that the coolant has to go somewhere, so where is that somewhere? If you have no wetness or puddles, then it is migrating to another system, and the likely place for that is the head gasket. Think about it, the oil, water, intake and exhaust all meet at the head.

    I recently had my C10 pickup develop a pinhole on the side of the head, under the intake manifold. You couldn't see anything leaking, but you could hear water dripping on the exhaust. /forums/images/graemlins/frown.gif
     
  11. femur

    femur Newbie

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    valve ring

    So on the new fixer I have found that it burns oil and it is due to my valve ring, and for some reason it will fould a plug once it has been pushed on for so long is all this caused by the valve ring?
     
  12. dhcomp

    dhcomp 3/4 ton status Premium Member

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    Wait, our trucks arent' supposed to smell like burning oil? Dammit....

    My 94 350 TBI stinks of oil at startup...and when under load at high RPM. But oil is cheap, and repairs aren't.......and its been like this for 70k.
     
  13. sandawgk5

    sandawgk5 3/4 ton status

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    Bad Valve stem seals will let oil past the valve stem and into the flow of fuel and air and therefore into the cylinder. This will foul plugs and obviously cause it to burn oil.

    Ira
     
  14. merace19

    merace19 1/2 ton status

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    pcv valve will cause it to suck oil into the intake and burn it.
     
  15. diesel4me

    diesel4me 1 ton status Premium Member

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    intake or gasket too..

    I've seen high milage motors that started smoking suddenly (and still had good compression when I tested them),they turned out to have a intake manifold that cracked under where it sits over the lifter galley,and it sucked in oil and burned it--it took that motor several minutes to start smoking after a start up,it took awhile for the crack to open up as it warmed up--the idle got poorer as it warmed up too, due to the vacuum leak ,and oil getting on the spark plug in that cylinder....

    Another engine (scrapped by my friend,who labeled it "junk"),had a intake gasket that lost a chunk where the intake and lifter galley is,and did the same thing,plus skip like it had a dead cylinder...ran perfectly again with a new intake gasket and an aluminum intake I had lying around I swapped onto it..:laugh:

    I have seen pistons lose or melt the top "land" above where the first compression ring goes ,and make the motor smoke suddenly--same goes for cracked or broken piston skirts..usually pinging causes this type of piston damage...on other motors I have seen the rings stuck to the piston so bad you had to use a chisel and hammer to get them off the pistons,bonded in by heat and combustion chamber residue..

    A compression test or leakdown test helps pinpoint what the problem is..if it has good compression its likely a PCV system problem ,or perhaps gaskets or intake woes as described already..valve stem seals usually make smoke as soon as it starts and gradually it goes away..they let oil drip into the cylinder overnight or after sitting awhile..a bad valve giude can cause smoking too,but usually the motor wont idle good if they are that loose..



    :crazy:
     

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