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Thread: 99 ford 7.3 disappearing oil

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  1. #1
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    99 ford 7.3 disappearing oil

    so yesterday i ran my truck damn near out of fuel. started loosing power with less than 1/4 tank left so i pulled over, shut it off and dumped my big jerry can of diesel into the tank. started and ran great, stopping to fill tank on way home. drove it last night, all was good.

    then today, went to drive it into town, ran like a bag of chit when reached 3000 rpm in second gear, blowing smoke out the tailpipe. third gear, same. couldn't get past 60kph. pulled over, oil pressure dropped. got out, checked oil, none on dipstick.
    went home, grabbed 15 liters of oil, filled it up, ran fine. drove it back home and parked it.
    went to drive it to town again this evening and again, while idling, started running rough, watched oil gauge drop to zero. checked oil and again none there.

    it isn't leaking on the ground, not smoking while driving, runs fine when full of oil. don't know where it is going. always use royal purple since the engine was swapped at beginning of year.

    is there a way for it to leak into the fuel tank?

    99 ford f450 7.3 standard 5 speed with bull low.
    Last edited by caged; 10-22-2015 at 10:54 PM.
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    even if it leaked into the tank, you would see it in the smoke, you would also smell it. that's not to say it can't get in, but something would need to act like a vacuum. we are talking 15L min, possible 30L I'm sure you would see it on gauge.
    just for laughs have you checked the coolant.
    it just makes more sense!
    a learning experience is one of those things that says, you know that thing you just did...don't do that again.

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    Running out of fuel with 1/4 tank left?


    I think fuel may not have been the issue but letting it cool down addressed your issue temporarily. The huge consumption of oil is worrying. Not sure your total oil capacity but on my Cummings it is 13l I believe from empty with filter change. So yours needing 15 liters makes me ask did it disappear all at once or little by little and no one was checking and now the damage is done and .......

    Lots of variables and without knowing your mechanical aptitude I don't even know what to ask next. My old 12v Cummings would send small amounts of oil out the crankcase breather so a catch can kept the driveway clean but since you don't speak of dropping anything the motor got hungry and ate it. 15 liters doesn't disappear and you can't fit that much oil in the coolant without noticing it. Sounds catastrophic in one way or another. Drain the oil and see what you see. Personally I would be looking for a diesel compression test if the oil drain doesn't come up with glitter.

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    That powerstroke has hydraulically fired injectors which use engine oil. There is a high pressure oil pump (HPOP) that pressurizes the system. If this pump runs low on oil, there absolutely could be drivability issues since the injectors will not be firing properly. For the most part, the 7.3 HPOP is a fairly robust unit and known for being quite reliable compared to the later versions.

    The biggest issue is where the fuk is all of the oil going? Since an external leak of that magnitude should be obvious, the typical other logical explanation is that the engine would have to be burning it off. I would check the crank breather for any excessive amounts of oil or obvious excessive flow and pressure. If there is a lot, there might be an issue with rings and/or a piston.

    HOWEVER, and this is a big however, because of the nature of this somewhat unique fuel system, it IS possible for bad injector O-rings to pump engine oil back into the fuel system via the fuel return at the fuel filter.

    Check the fuel filter for signs of engine oil. If it is there, it could be simultaneously be pumping oil into the fuel system at the engine via the filter AND returning some to the tank.

    Let us know what you find. If that is the problem, replacing the injector O-rings should solve the problem.
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    bingo, i think you nailed it. took off the fuel filter and yep, full of oil. so i dropped it off at the mechanics and he said the same thing, so it's getting new injector seals to start with.

    and no oil in the coolant, good thing.

    i did fill the tank and it doesn't move off full for quite a while, and it was still on full after driving it for that little bit where i guess it should have at least come off the full mark.

    i will let you know when i get it back from the garage.

    thanks guys.

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    Cool. All in all, it is a pain in the ass but could be a lot worse. It sounds like it must have completely blown o-rings right out. Looking forward to hearing the outcome.

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