520 breather line

jdfamily · Jan 5, 2018

I have a nice 520 John Deere runs great. Question, what is the purpose of that small pipe that runs from the governor housing into the air intake going into the carb? Just recently that line started leaking oil.
I did not think there was supposed to be oil in that line?
Any help appreciated.
Thanks

4play · Jan 5, 2018

If you have oil in the breather line it is probably caused by blow-by gasses from the crankcase, blow by gasses carry oil mist and it flows through the breather tube. I'm not saying you have excessive blow by but that's what happens or gets worse when you do. A worn engine, mainly piston rings is the usual cause of excessive blow by. Your oil is level is probably ok but if it's overfull that can sometimes cause more oil mist in the breather tube.

Bob · Jan 5, 2018

This system works differently from engines where the crankcase ventilation system is simply vented to the intake air system.

There's a ventilator pump in front of the governor (the fanshaft drives it) that draws clean air through the tube from the air intake ahead of the carb and forces it into the crankcase, which pushes combustion byproducts out of the crankcase, to the valvecover, and out to the atmosphere through the crankcase vent tube hanging below the valvecover.

For oil to be moving the wrong way, and entering the air intake system, either the ventilator pump has failed, or your air cleaner or air intake system are clogged up and sucking air backwards through the ventilator pump. Or, the engine has a TREMENDOUS amount of blowby.

<img src = "http://oi64.tinypic.com/2u56zc7.jpg">

The ventilator pump components are shown at the lower left area of this parts breakdown. If power-steering equipped, ventilator pump is the same, but PS pump is also driven by the fanshaft

jdfamily · Jan 7, 2018

Thanks I appreciated the information. Will do some checking based on your comments. The tractor does not take oil, and the compression is
good on each cylinder. Guess looking into the venting system is next. It does have power steering so my thinking is that will make it a
little more difficult.

520 breather line

jdfamily

Member

4play

Well-known Member

Bob

Well-known Member

jdfamily

Member

Similar threads