2009 yz450 oil tank breather hose???

2 replies to this topic
  • diamonddave66

Posted November 27, 2011 - 06:25 PM


Was wondering what goes thru the oil tank breather hose, oil,coolant or air? Its the hose that connects just under oil filter cover and runs up and connects right beside the oil dip stick. After riding today noticed what appeared to be coolant on and around the hose at the bottom. My coolant level was pretty low. I did dump the bike over on the right side in a turn today. Just wondering where coolant came from? Can't get it to leak at home.

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  • grayracer513

Posted November 27, 2011 - 10:01 PM


The function of the hose is to balance pressure between the crankcase and the oil tank. Normally, only small amounts of air need to move through it, but excess oil will, too, if the unit is overfilled.

The coolant leak is more probably coming from the water pump. The pump has an oil seal and a coolant seal separated by and air gap that leads to a small port in the right crankcase cover, behind and below the pump. Often times, the pump will leak only when running, or only when sitting, but not at other times. Dusting the area with baby powder can help verify the leak.




  • diamonddave66

Posted November 28, 2011 - 12:41 PM


Thanks for the info .

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