Posted by wxford on November 02, 2012 at 17:38:04 from (188.8.131.52):
My lawn tractor is powered by a B&S Vanguard 303447-1147 that is about 15 years old with about 700 hours on the engine. It has performed flawlessly mowing about 2 hours per week – until this spring. Early this spring I serviced the unit and changed to the recommended synthetic oil for the first time. As I began using the tractor, I noticed that it was throwing a LOT of oil. I discovered that the dipstick tube seal-ring had deteriorated – replaced it and the o-rings on the dipstick cap and valve cover oil fill cap.
However, the engine continues to blow some oil through the breather assembly as confirmed by the oil collecting in the air-cleaner base, but in much smaller amount (about a pint every two hours of running). I've replaced the breather assembly (PCV). The leak-down test is about 8% and seems to be the same for both cylinders. I've checked the valve seals, and the left side cylinder has a seal on the exhaust and intake (I don't know why). The right side has the valve seal only on the exhaust valve (as it should).
I continue to believe the engine is still sucking air via a crankcase leak. I'm aware that any small air leak can cause this, but am unable to locate the source of the problem. Any ideas?
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