Second Hose from Valve Cover (Not PCV) What is it?

Hehe… i thought i was just going to “lurk” here bc im using my phone and its a bit maddening but… i just couldnt help adding my 2cents

Every garage has an entity that asks questions that might seem designed to send you to a quiet corner of Shady Maples sanitarium however since these questions are mechanical in nature and seem to fall well within my narrow breadth of knowledge i actually have to let them slide

Hey where else can i (or we) look wise?

So i say… think those mechanical thoughts and ask those questions… Lord knows that i ponder questions that are waaay more far out than what we have seen here… im just getting better at not asking them out loud.

Keep those questions flowing and stay curious


If there is ever a sense that car related questions of any kind aren’t welcome on this site, then this site needs to shut down.


Newcomers must run the gauntlet @JoeMario. We must keep up traditions to keep the riff-raff out by restricting membership.

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I not sure what a oil catch can would do for you. I guess if you put a coallising filter there you could stop some of the oil in the blow-by gasses from being burned by the engine. However the engine would still use the same amount of oil and you would have to peroidotically drain or change the filter. I guess that in extream cases it might help keep the intake a little cleaner but I don’t know if it would be worth the effort. I know there were a lot of the 2.4l toyota engines that had excessive oil consumption after about 50K miles. From what I have read, there was a problem with the piston oil rings from about 2000 to 2006. If you are having oil consumption problems due to the oil ring problem I doubt anything you could do with with the crancase ventilation would help. If you are not having problems then I wouldn’t change anything the engineers that designed the system know a lot more than I ever could:)

You need to replace it if it is cracked or has a hole in it. The PVC is sucking vapors from the crankcase which creates a vacuum inside the engine in the crankcase and under the valve covers. The two are linked by the oil drain back holes.

The hose is after the MAF because it accounts for the air being drawn into the intake manifold that did not go through the MAF sensor. In other words, the PCV air is not accounted for but the makeup air is accounted for so it all balances out and your engine runs the way it should.

A breached makeup hose could cause the engine to set a P0171-P0174 code or codes.

You’re late to the party

Volvo told him to replace the hose a few days ago