fenixnano

I got a 1997 LS400 and it runs pretty good so far.
however, today I just noticed that a hose on the engine is totally broken off.
seems it's supposed to be connected to the air intake but I'm not sure.







I tried to check other threads, but I don't know how to describe it. is it pps hose? or IAC? but pictures in other threads seems only have one hose in this position, where I seems to find 2. so I got really confused.



seems the plastic part where the nozzole came off is blocked by some metal??




so could anyone tell me what is this hose and is it a serious problem?

the car is still running and there is even no check engine light....

Thank you!

fenixnano

btw I do noticed some noise in the engine, sounds like a broken bearing or something.
and when making turns, the power steering is making a whining noise, which is the reason I'm checking and refill the power steering fluid. that's when I noticed this hose issue.

oldskewel

iTrader: (1)

Don't worry, everyone breaks that thing off by accident. I know I did. It goes from that intake plenum to the idle up air valve on the PS pump.
The barb end, and the hose itself get brittle with age, making it easy to break.
You can easily fix the plenum with a brass or plastic barb to screw in there, or I just used a piece of hard brake line pressed and glued into a carefully drilled hole.
Then run a new vacuum line to the valve on the PS pump, and also the other line coming out of that valve and going to the intake manifold.
Make sure your PS idle up air valve is not leaking, while you're in there. Commonly know to damage the alternator, which is underneath it.

17630-16040 is the part number for the valve on the PS pump. Search on that, and you'll find a lot more info on this very common issue.

RA40

iTrader: (6)

Yup, the plastic is pretty brittle, broke mine too. Easily fixed, several options, plug it and run a T-fitting to the other hose or patch the broken attachment.
This is what I did here:
https://www.clublexus.com/forums/ls-...e-fitting.html

fenixnano

Thank you!
so this hose is really supposed to link to the air intake?
I'm just wondering why a vacuum line would be connect to the air intake, which would have unlimited air.

oldskewel

iTrader: (1)

It's the way the idle-up air valve on the PS works.

That valve (PN given above) detects when PS pump pressure is called for, and when that happens, it opens. This then provides an AIR path from that broken-off barb on the plenum, all the way through to the intake manifold. Allowing a little more air to flow there does a similar function to the idle-air-control-valve, or stepping on the throttle, causing the engine idle to increase slightly (or at least not drop) to provide power to the PS pump when it is needed for low speed turns, like when parking the car.

So when that valve opens, yes, the intake manifold vacuum will suck air from that broken plenum, through the first hose, through the valve, and through the second hose. All things are sized properly to provide the desired increase in engine RPM and resulting steering power.

When your PS pump is not asking for extra RPM, that valve is closed, and the whole system may as well be plugged. Some people resort to doing that when the valve fails, removing the low-RPM PS boost feature.

That valve often fails, and when it does, PS fluid will leak past the valve and into that hose. Then when the car is started after sitting for a while, all that PS fluid is burned quickly, producing the infamous white cloud of exhaust. It also of course depletes your PS fluid.

spuds

Great info posters,much appreciated,bookmarked.