Power Steering Pump/Valve

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awinata

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Location
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Those of you who own a first generation Lexus (90-94) with mileage over 100k bound to experience power steering leaks (if not already). Usually, the valve is the culprit (due to heat)... replacing the pump (and valve) will fix the leak temporarily (it WILL leak again). One solution is to bypass the valve... (1) loop the hose from the pump (valve) to itself (or better yet, remove the valve completely from the pump and plug the hole), and (2) loop the hose from the air box to the engine vacuum. Any comments on this procedure?

Asher
 
I don't think it's a good idea to loop the hose from the air box to the engine vacuum port. I suspect this will make the engine idle faster. Normal operation is that when the pump is under a load ((turning the wheels), the valve opens allowing more air into the vacuum port and increasing the idle speed. Perhaps the engine control computer can compensate for this extra air. A better plan would be to plug both hoses. I did this on my 91 LS400, after I replaced the pump. I didn't replace the valve. I just found a leak on my 94 LS400 with 71K. Looks like it's time to remove the valve on this one.
 
Yes, you are absolutely right... it will affect the idle but I barely notice it though. Lexus is so quiet and smooth you barely notice any subtle changes in idle... amazing car.

What would happen if you plug both the air box and the vacuum port? Do you think this is better than looping the hose from the air box to the engine vacuum port?
 
OK... so you are saying that if I remove the valve and plug the hole I will solve this problem? Do I have to chage my already leaking PS Pump or just remove the valve.
 
Hi, I have this pump problem, can some please post a picture of this valve? Im a newbie and any help or a walk through would be great.
My car puffs white smoke from the exhaust when started and I have read this is related to the PS Pump valve issue, is this correct?
 
If the leak is from the valve then it should solve the problem. If not, I would solve the problem first and then plug it anyway to prevent future problems (the leak problem usually comes from the valve - it made of plastic and cannot withstand the prolong heat from the engine). Let your mechanic do it for you, it's not easily accessible from the top.
 
Valve opens when you turn the wheel to let more air into the motor, thus enabling idle to remain while power steering pump is under load.

I hope that makes sense.
 
Does the sc400 have problems with the valve,(i don't where it is) cause i replaced my power steering pump tonight and it was still making a grinding noise when i started it. I haven't fully bleed it yet, but i'm scared that the pump was not the problem, as it had already been replaced at 53000 miles and i'm putting this new one on at 97000?
 
On my '91, the pump itself was leaking first. I had purchased a seal kit from Lexus, but had not installed it when the alternator quit due to leakage from the power steering pump. I bought a new pump and alternator. Sometime later at about 170K, the bypass valve started leaking. This lets power steering fluid into the intake manifold. It fouled on of the spark plugs. That is when I replaced the valve with the bolt and blocked the vacuum lines. My '94 had the same leaking problem at 80K. Replaced the pump because the valve was still OK. Make sure you have enough fluid after replacing the pump. Insufficient fluid will ruin the new one. Fill it a little over full and pump by hand the try to get out the air. Then start the engine. Immedy stop if you hear noise and add more fluid. Start again and noise should stop. Turn the steering wheel back and forth 3 or 4 times to get all the air out of the system.
 

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I bled the system by removing the upper return hose on the reservoir and holding my finger over the outlet on the reservoir. I put the return hose into a mason jar and had someone start the car and shut it off as fast as possible to allow the pump to pump fluid and the air out. I then refilled the reservoir with the fluid captured in the jar and did this process maybe five times. I reattached the hose to the reservoir and the pump stopped making noise and worked great because the air was now out of the system. This process is similiar to what it said to do in the lexus factory repair manual, anyway i'm happy not have problems with any valves!
 
Bad news, for a few days after my power steering pump replacement the steering was light and fine. Lighter than it used to be with the old pump, which also may the car feel so heavy and slow. Well, it know the steering feels heavy again and it makes the driving experience suck. I even bled the system again, but found no air in it. The fluid was already pretty dirty and had a strange smell to it after only a few days. I read somewhere that the most common cause of failure of a powersteering pump is deteriorating hoses. This would make sense in my case since the car is a 92 and the previous pump had already been replaced and the seal was not leaking when i changed it. It was just grinding like hell and not providing any power steering. My other question is whether i have a problem with the speed sensitive power steering, like it is stuck in stiff mode all the time even at low speed driving. Anyway, this is getting frustrating, thoughts?
 
Did you change the fluid? The fluid on both of my cars ( '91 and '94) looked and smelled fine when the pump was replaced. I didn't let the old pump get too bad before replacing it. It was just leaking, but not making any noise. You may have contaminated fluid if the pump ran dry between refills while it was leaking. My manual indicates that the PS system will not work correctly if there is air in the system. Also, you need sufficient pressure. Insufficient pressure may be due to the pump or the control valve in the gear housing.

Do you have a manual?

On my '94, I used a turkey baster to suck the fluid out of the resivoir and then refilled with new fluid. I did this a couple of times. This changes a portion of the fluid and also doesn't get any air in the system. Hopefully, the pump will last a little longer.
 
I don't think this pump got too bad before replacing it, it did not leak, so i didn't know it had a problem until it started to grind, which it had a slight whine to it since i bought the car. 1st power steering pump was repalced at 53000 miles and this one i just replaced at 97500 miles. I have a manual......if you look back a couple of posts you can see a did a full bleed and flush when i put the new pump in a few of days ago and it worked great for a few days. I don't know what went wrong, besides that the steering is heavy, as it used to be with the old pump. Only did I realize how it is supposed to feel, light and crisp, is when i changed the pump and for a few days it was lite and easy to drive, also I have only owned the car since 87500 miles so I didn't know how it was supposed to feel, although i couldn;t beleive how heavy the steering wheel was when i got until i changed the pump. Control valve problem? Deteriorating hose problem? Help!!!!!!!!!!
 
Do you think you changed enough fluid? Since the old pump was grinding, maybe you have some debris in the system. I would try flushing the system again to try to get the fluid looking and smelling good. Are there any metal particles in the fluid you removed? My '91 still has all the original hoses at over 200K miles. My son is driving it now.
 
A few days ago I flushed it thouroughly again with almost 2 quarts of ATF by removing the return hose pumping the old stuff (about a week old) into a jar, while only putting in new stuff into the system. The system only holds a little over a quart total according to my book, so the car definately had all new fluid and the fact that it was coming out nice and red. I drove the car and it might have gotten slighly better, but not really, the steering is too heavy. There must be another problem. Also, its been a few days so i need to check how clean the fluid is, due to my theory of rapid hose deterioration. Anyway, the lexus manual has a few simple checks for the steering ECU and solenoid, which i haven't done, but i really suspect the control valve in the steering rack. I live in a rural area and am going to Austin, TX next weekend, I'm thinking about taking it into the Lexus dealship for a diagnosis. They can test the pressure the pump is making (according to the manual over 1,000 psi) and anything else because alot of this work may require special service tools and a lift. I'm suspecting my second powersteering pump failed so quickly because something else is not right in the system and am hoping it has not already damaged this new pump. Does anyone know if i buy a new steering rack, if the control valve comes with it, because in the service manual it shows how to remove it from the rack and replace or reinstall, so i don't know if it comes as an individual unit?
 
Okay, the car's powersteeing system seemed to be working fine since that point, and now i've driven about 3,000 miles with the new pump. The last few days here it has gotten cold and again i heard that old psp grind, and my face went arg! I checked the fluid and it seemed to be fine so i drove the car and the sound seemed to go away. I added some fluid tonight anyway, since it might have been a bit down and started the car and indeed it had some whining to it. It did this for about 5min, then as i waited for my McDonald ceasar salad at the drivethrough i turned the wheels left to right fully several times as i remember the manual instructing to bleed air. By the time i got to my friend's house i couldn't hear any whining (about 15 min from start-up). So is this just a symptom of the cold, or is the cold revealing an existing problem. I remember from a the 3 months ago when i changed the pump that the passenger side rack boot looked wet so there is a slight leak there, perhaps it has leaked and allowed air into the system, or perhaps more complicated things are happening which i don't have the ability and didn't have it checked which could involve the powersteering progressive system, including the ecu and control valve and solenoid, any suggestions? I can't beleive how complicated powersteering can be!
 
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