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)

 

Hello...

I have been studying prius engines for at least a month because I want to buy a prius V... I think the top hose that goes to valve cover is "filtered" AIR INTAKE accounted for by MAF sensor on behalf of the coumputer and the bottom of the engine hose is AIR OUT of the crank case housing via PCV circulation system going into high vacuum intake manifold behind the throttle body aparatuus so that it is constantly via strong vacuum replacing or ventilating air trough the engine to mix with blow by gases of piston rings and this air is filtered and accounted for by the computer in terms of fuel air mixture calculation...
but ... and for the sake of convenience as in closer and shorter hoses TOYOTA in my view has gotten these hoses backwards .... SO I woud have ventilated internals of combustion engine crank case from "bellow to the top" direction and then I would have gotten all the water steam vapours out at the top of the valve cover and then there would have been less oil build up in Prius intake manifold such as it is now (but add oil catch can still of course) and then there would be less oil to mix with carbon in the intake manifold to then gunk up the EGR ports at the valves in the intake manifold that are small and get pluged with carbon from recirculated exaust gases anyways but oil there just makes it worst...
but that is only my opinion and I am NOT an auto engineeeer
I am a computer scientist (dam it) and amatour radio KG6AFF...
so... I still want to buy one prius V oct 2024 ...

who wants to sell me one!!!

call me: 541-390-3663

(I can fix anything except head gasket troubles)

-tibor