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B&S oil leaking into air filter?

Discussion in 'Mechanic and Repair' started by Shawn's Lawn, Oct 7, 2003.

  1. Shawn's Lawn

    Shawn's Lawn LawnSite Member
    from Texas
    Messages: 40


    I have a briggs that is leaking oil into the air filter, I was wondering if anyone had any suggestions on why this is hapening?

    thanks for any help....
  2. mower_medic

    mower_medic LawnSite Member
    Messages: 77

    what size B&S? On some of the twin cylinder Vanguard engines, I have seen a blown head gasket cause the air filter to become saturated with oil.
  3. Shawn's Lawn

    Shawn's Lawn LawnSite Member
    from Texas
    Messages: 40

    Sorry for not getting out all the facts....

    it is a 5.5 quantum, it starts up and runs... it did however smolke since the iflter at the time was saturated in oil.. once replaced, it runs without smoking.. also when I open the oil cap smoke is coming out...

    thanks again.
  4. barnard

    barnard LawnSite Senior Member
    Messages: 618

    Either you have a worn out engine with blow-by past the rings or your tipping the mower on its carb sde when cleaning deck etc.
  5. Dave_B-The_Grass_Guy

    Dave_B-The_Grass_Guy LawnSite Member
    Messages: 18

    You didn't say wether the smoke from the oil cap was during or after it was running. Either way, its blowby past the rings, and even new motors will get a little of that. I don't think it's a blown head gasket, those engines are esentially a 1 cylinder flathead, you blow the gasket on them and even if they do run, they will spray oil all over the deck.

    Tipping the mower onto the carb side can allow some oil past the rings and into the carb, but I doubt it would be enough to make it up into the element. Overfilling the crankcase with too much oil will cause excessive splash in the crankcase, resulting in the excessive crankcase pressure(a-heat expansion and b-the aforementioned ring blowby) to cause the extra oil to escape via the vent tube which feeds into the air intake. Although I have never had the experience to actually work on a quantum, the design behind the 1 cylinder B-n-S's is still essentially the same. They all have a tube that vents into the intake, some directly into the carb, others into the filter housing.

    Check your oil level 1st, make sure it isn't past the top line. Store it on a level surface when not in use. If it persists, see a mechanic, the rings may be shot, or the valves seats may have receded, causing the valves to float a bit(briggs are notorious for that over the years, shaving the valve stems to obtain .008 clearence with a belt sander or grinder fixes it, but this is rare unless the engine has seen over 100 hours). Either way it should be done by a compitent mechanic, as reusing the headgasket is iffy at best on a used motor.
  6. barnard

    barnard LawnSite Senior Member
    Messages: 618

    Dave , tipping the motor on the carb side doesn't let the oil past the rings. The oil comes from the crankcase through the crankcase ventilation tube and into the carb. It can saturate the air filter with oil in short order. I have" repaired " several of these returned to our local big box store.

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