Oil coming through intake

HEIDE1234

MEMBER
2005 MAZDA 6
3.0L
V6
2WD
AUTOMATIC
143,000 MILES

Just bought this car it is a hatchback. It did not run got it for cheap. As I did an initial look over I pulled open air box and there is oil inside the hose to air box. I have researched a little bit an have come up with PCV valve failure possibly? What else or what could caused oil to be pushed through top end? It could have been overfilled I have no idea and cannot contact previous owner. It is enough oil in the air pieces that it is quite alarming. When I first turned the car over to see if it started it turned over slowly like battery was almost drained but there was no squeaking or noises so I do not think it spun a bearing. Just needing some help in figuring out the cause so I can fix it.

2 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning.

The first thing I would do is a compression test. It sounds like you have either very worn piston rings or piston damage. Either will cause oil back through the intake.

It looks like the reason it was sitting so long and why you got it cheap. The previous owner was most likely told of the issue.

Roy

https://www.2carpros.com/articles/how-to-test-engine-compression

https://www.2carpros.com/articles/replace-engine-piston-rings

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Tuesday, July 3rd, 2018 AT 3:31 AM

DANNY L

MECHANIC
5,648 POSTS

Hello, I am Danny.

Yes, you are correct about the PCV valve/system. The purpose of the PCV (positive crankcase ventilation)is take all the fumes/gases from the combustion process that have entered the engines crankcase and route them through a hose and valve (one-way check valve-The PCV) from the valve cover to be resent back through the engine to be reburned. It is normal to see some oily deposit, but not a swimming pool. It is possible the PCV is stuck open allowing excess oil in when engine is shut off. High mileage vehicles/worn piston rings can cause excessive blow-by to contribute to the extra oil. PCV valves are inexpensive ($10.00) at any auto part stores and are easy to replace/install. I have attached a picture and circled it in red to show the location. Hope this helps and feel free to ask any questions if needed. Danny-

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