fisher972002 Posted October 14, 2011 Posted October 14, 2011 Hi all, 1991 LS400, 196K miles. Power steering whine, air in PS system. Last Feb, the original Rack/Pinion was leaking. Obviously a problem there, but before I had the dealership replace the rack, I replaced the PS Pump with a Napa PS pump. I noticed the PS reservoir is missing the screen inside it. When it was off, you can see daylight from where the rubber tube connects and through the bottom of it, it is basically hollow...I replaced pump, no change. So, in Feb dealership replaces rack at cost of $1500. QUieted down Whine when you drive around town, you can basically drive all around town and no whine even when hot. Problem is when I get on the highway high speeds, and drive more than 10 or 12 miles then you pull off the exit ramp it starts wining... So I do the Bleeding procedure outlines in ALLDATA, keep the RPM's below 1200, open the reservoire cap, turn the steering lock to lock 2 or 3 times, turn off car, see if bubbles... Of course bubbles come up.. I will do this on the side of the exit ramp 2 or 3 start/bleed cycles and it will bleed off... THen be quiet again, until you run again on interstate and whines again. No visible leaks..I replaced the High Pressure hose when I did the pump with a new aftermarket hose. THe return hose, I didn't buy the lexus one, just used universal hose and hose clamps.... I've taken it back to the dealer twice, explaining that you have to drive at high speed for a while to get it to really whine... THey say they can't duplicate it.....and the PS system is fine, but I know it is not.... Few things I thought of, is fluid cavitation, you know if there are 2 types of fluid, but that is not the case I use the Wynns' PS Fluid provided/bought from the dealership..... I'm wondering if the PS reservoire missing the screen, maybe the fluid is flowing too fast and cavitating at high speeds.... About the only thing that hasn't been replaced, is the Reservoir, and the Vacuum booster on the side of the PS Pump, the low RPM boost component with the 2 vacuum lines going into it, the idle air valve I think it's called... Out of ideas, anybody have any ideas...
DEATH Posted October 14, 2011 Posted October 14, 2011 About the only thing that hasn't been replaced, is the Reservoir, and the Vacuum booster on the side of the PS Pump, the low RPM boost component with the 2 vacuum lines going into it, the idle air valve I think it's called... Out of ideas, anybody have any ideas... The reservoir is where the screen should be. If it's clogged, that will cause noise. The return hose to the reservoir can get very brittle and suck air after time. The VSV to raise the idle that is screwed to the side of the pump has a small plug in it that needs to be transferred with the switch when you replace the pump. If it's missing, it can cause a buzzing. Also, there is a screen in the rack that can get clogged. It's beneath where the pressure sensor screws on.
billydpowell Posted October 15, 2011 Posted October 15, 2011 just a passing thought..... IF after driving on the interstate, the heat causes the fluid to boil and that is where the bubbles are coming from, because the missing screen actually slows down the flow of fluid to prevent this. you might also want to read this from 2003-2011 postings. http://www.lexusownersclub.co.uk/forum/index.php?showtopic=8910
fisher972002 Posted December 2, 2011 Author Posted December 2, 2011 Hi All Just thought I'd post back the fix for future searches. It turned out to be a combo of 2 things... #1 The air Control Valve on the side of the pump, Lexus/Toy Part # 17630-16040. It had a slight leak visible on outside, and inside the vacuum piping tubes we found some PS Fluid. I think it was seeping air somehow into the system perhaps when the car was off and still.... #2 and probably more important, I replaced the low pressure reservoire return line that hooks into the side of the pump reservoire. The factory one was all cracked and hard.. I made the mistake of putting on regular cut by the foot tubing from the local auto part store... We noticed that even though the piping fit over the reservoire and return line ok, it was kind of thin-walled and on the curve of the piping, the rubber hose was flat/ from the sucking pressure..... I believe I was unable to bleed the system because of the cheap rubber tube being flat and not holding it's form and the air bubbles couldn't clear up... AFter replacing all the leaky PS parts, Rack, HIgh pressure lines..I replaced the reservoire Rubber tube, not with the Lexus part that is $150 Dollars, OMG, for a freaking rubber hose..Ugh.... I replaced with a larger thicker walled rubber hose/tube that will keep it's circular form better .... Also after doing the LExus bleeding precedure, I still had a ton of air in the system.. We used a vacuum gun, Idled the car, put the vacuum gun on top of the reservoire, added slight vacuum, the pump would wine, wine and then slowly turn... The added vaccum cleared up all the air bubbles and eventually after about 10 minutes of this it cleared up... I have my LS PS back like normal and it FEELS SOO GOOOOD... Steering w/ Pinky again..LOL...
landar Posted December 3, 2011 Posted December 3, 2011 So the bottom line cause for the PS pump whining was a restriction in the system which was caused by a pinched return hose which, in turn, caused cavitation and air bubbles in the system. Good post.
lenore Posted December 3, 2011 Posted December 3, 2011 Also note that as lines age sometimes they expand internally and cause flow blockage...Had this happen a couple of times on Brake systems...The rubber hoses apparently do break down.
landar Posted December 3, 2011 Posted December 3, 2011 Also note that as lines age sometimes they expand internally and cause flow blockage...Had this happen a couple of times on Brake systems...The rubber hoses apparently do break down. I believe that you meant "collapse internally" but yes, you are absolutely correct otherwise. I have had it happen on several Chrysler brake systems which resulted in stuck/dragging brake calipers.
fisher972002 Posted December 6, 2011 Author Posted December 6, 2011 That is correct Landar. Lenore, you are correct, although in this case, the line was only a year old.. SO it wasn't a problem with the return line connecting to the reservoire, breaking down, the line was fine rubber quality wise, it was just too thin... Too thin walled of a hose to make the extreme angle of the reservoire connector down to the PS line... Now we know, examining the factory line, it is really thick and robust.. THis is why.. So if you don't want to spend $175 on a new factory lexus return hose, don't just get the run of the mill pay by the foot hose for this, find a thicker walled hose that will maintain it's shape...or basically the rubber hose didn't really break down, it just couldn't handle the angle w/out sort of folding flat...
landar Posted December 6, 2011 Posted December 6, 2011 I have also used a Gates unicoil to keep the hose from collapsing on a bend. -> http://www.gates-unicoil.com/
fisher972002 Posted December 20, 2011 Author Posted December 20, 2011 Guys, also for future searchers, to replace the PS reservoire return tube sub-assembly 1, LEXUS part # 44406-50010 that tube is $173.86.. replace not with a standard cheapo 3/8" PS return hose, but instead get the Gates Transmission Oil Cooler hose. It has fiber reinforcement and is much sturdier tube than the standard PS return hose that will fold over.. The Gates part # is 27057, get the 3/8" diameter hose and should be good to go.. Also use the Lined Hose Clamps, so you don't dig into the hose...
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