# Oil in the Cold Air Box?

**URL:** <https://community.cartalk.com/t/oil-in-the-cold-air-box/60351>\
**Category:** Maintenance/Repairs\
**Tags:** chevrolet, cavalier, oil, leaks, engines\
**Created:** [January 23, 2011, 4:42am UTC](https://community.cartalk.com/t/oil-in-the-cold-air-box/60351 "2011-01-23T04:42:52Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![cyberyukon](https://avatars.discourse-cdn.com/v4/letter/c/fbc32d/32.png) [@cyberyukon](https://community.cartalk.com/u/cyberyukon)\
**Post date:** [January 23, 2011, 4:42am UTC](https://community.cartalk.com/t/oil-in-the-cold-air-box/60351/1 "2011-01-23T04:42:52Z")

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The cold air box is a black plastic box that sits forward of the engine/valve cover. It connects via black plastic tube to the air filter box on one end and to the engine on the other. I took it off it. 'Lo and behold it was full of oil. Any ideas?

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**Author:** ![BustedKnuckles](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bustedknuckles/32/25_2.png) [@BustedKnuckles](https://community.cartalk.com/u/BustedKnuckles)\
**Post date:** [January 23, 2011, 5:08am UTC](https://community.cartalk.com/t/oil-in-the-cold-air-box/60351/2 "2011-01-23T05:08:28Z")

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You have a lot of blow-by, and the crankcase gases are bqckflowing through the vent tube into the intake hose and the air box. You’ll see one or two smaller hoses attached to the plastic tube, about 1/2" diameter. One of these connects to the valve cover. This is supposed to be the fresh air feed to the crankcase ventilation system. A plugged PCV valve or worn piston rings are allowing the crankcase pressure to be elevated, letting crankcase gasses and oil to be ejected through this smaller hose, and this oil is getting collected at the lowest point, the air box.