For a while now, my power steering on my 2000 LS has been stiff while turning the wheel. It also has a constant whining noise (almost like a supercharger) at idle and higher rpms. I've replaced the power steering pump and tried a few times to bleed air out of the system by jacking up the front wheels and turning the wheel lock-to-lock (with the engine off). The power steering fluid level seems to be fine from day to day. I've been using Toyota ATF T-IV fluid (edit: haven't been able to find a straight answer on what to use. Looks like I'll be trying Dex III).

My next guess is to check the two rubber hoses that go to the air valve (the piece as shown below). How do I know which hose goes to which nipple on the valve? Im sure I've gotten them flipped at some point.

Long story short, I'd like suggestions on how to finally get the power steering noise to go away. Thanks.

 

Toyota T-IV is not the correct fluid.
Replace it with a Dexron III (equivalent)

 

As above try using Dexron II/III compatible fluid since that is what Lexus calls for.

 

This is the only diagram I can find that shows the vacuum hose routing.


Can the "nub" on the valve body (see OP image) denote if that nipple attaches to vacuum or atmosphere?

Note that the long hose is attached to the intake manifold; this is vacuum. The short hose is attached to the intake tract after the air filter; this is atmosphere.

I have never looked closely at the valve and I haven't found any reference to how the valve operates. I would proceed like this:

The valve operation has two possibilities:

1. It's operates one-way.
2. It's open both ways.

I'd pull a vacuum on each valve nipple (one at a time), to determine either 1 or 2 above.

If it's 1, the open valve nipple connects to the long hose.

If it's 2, the hoses attach to any valve nipple.

 

IIRC it does not matter how the 2 hoses are attached to the valve. The valve stays closed during normal operation but opens when the PS pump is under load. Low speed parking lot turning in and out of a parking space is one example. Any additional pressure inside the pump pushes the valve open which creates a loop of air circulation that flows accordingly. This small addition of air raises engine RPM’s slightly which in TURN (pun intended) spins the PS pulley a bit faster giving it a little more power which lessens the amount of force required to turn the steering wheel. Basically creating a high speed steering wheel feel at low speeds.

 

Thanks for the explanation. IOW, the valve is a metered vacuum leak operated by hydraulic pressure from the PS pump.

 

Yes.
Sorry, I was kinda long winded on that description...
To expand on the subject, the ACV is the culprit of the infamous puff of smoke at start up. The seals inside the valve become brittle after several years of use allowing PS fluid to escape into the air passages.
https://www.clublexus.com/forums/ls-...ring-pump.html