What Are The 2 Pcv Hoses On My Engine?

[perdaniel]

I recently noticed that there are two PCV hoses on my 2001 Avensis D4 (1AZ-FSE). One goes from the valve cover to the intake pipe (before the throttle body), and the other goes from the valve cover to the intake manifold (at the engine side). Why does the engine need two sets of PCV?

[frankie406]

1 vents the fumes from the crankcase and draws it into the intake to be burnt off for emissions.

[perdaniel]

1 vents the fumes from the crankcase and draws it into the intake to be burnt off for emissions.

And what does the other do?

[frankie406]

I believe it sucks in fresh air and pushes the oil vapour out into the intake to be burnt off.

[perdaniel]

That sounds strange. Isn't there usually vacuum in the intake pipe?

[frankie406]

Is one coming from air filter box?

[perdaniel]

No, one of them is coming from (or going to) the intake pipe between the air filter box and the throttle body. The position of both PCV hoses are shown in the illustration on this page: http://toyota.afora.ru/EU/AVENSIS/273540/AZT220R-AWMNHW/1201/26650/

[frankie406]

Hope this helps.

[perdaniel]

That might explain how it is supposed to work, but not why the breather hose is needed. It doesn't seem to work as intended, at least not completely, as there is oily residue in the breather hose. It is not as bad as the PCV hose. I checked the PCV valve, and it passed both the "rattling test" and the "blowing test".