What's this tube for? PCV line?

No, that's not the PCV valve hose. The PVC hose is down lower on the crankcase. It connects directly to the intake manifold, after the throttle body.

That's probably a valve cover breather hose.

Reconnect the hose and take it for a test drive.

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Here's what the Prius Gen 3 PCV hose looks like, it's the U-shaped hose on the left in this picture.

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Yep, that's the one pictured in my engine bay when I did that IM cleaning.

 

Here's my picture... without the hose.



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I wonder if that hose is tied into PCV system though; on gen 2 a hose like that has the pcv valve at the valve cover end.

 

Oh, it's definitely part of the PCV system; it's the breather hose shown at the top of this picture. It connects between the intake upstream of the throttle body and the valve cover.

Next down, the picture shows the other PCV hose, the little U shaped one, that connects between the manifold downstream of the throttle body and the PCV valve.

Flows in the breather hose can be either direction depending on circumstances. In times of high manifold vacuum, low throttle opening, the breather supplies fresh air into the valve cover, helping to scavenge out the blow-by gases through the PCV hose. In high-load operation, both the PCV hose and the breather hose are pulling gases out of the engine.

 

Thanks for helping us understand this... I was fairly certain it was part of the PCV system...

A couple questions:

1) Can this ever foul the air intake with oil if things go wrong?

2) Is this something Gen3 added than Gen2 doesn't have? Or same thing in both just different location?

 

The two hoses are pretty much the standard arrangement on anything I've worked on (other than a friend's 1965 pre-PCV Ford, which just had a filtered breather oil cap and a draft tube sending the yuck straight into the surrounding wind).

In the 1NZ engine, the two hoses run side-by-side.

 

That's the 2nd gen engine?

My hunch: it's better/safer to install and maintain an oil catch can in along the lower PCV line.

 

1st gen, 2nd gen, and c.

 

That's because he was explaining the difference between Gen2 and Gen3...

 

You would actually want to do the opposite. But leave it alone or put a catch can on.
(LS motors with undersized PCV systems push oil, but when you increase the size of the line it reduces the pressure and reduces the amount of oil they push through the PCV line into the intake)