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Power Steering ACV valve

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Old 11-08-10, 12:03 PM   #1
StevieA
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Default Power Steering ACV valve

Just replaced my PS pump & resovoir on the weekend (brand new $150 off ebay). We were worried that the ACV valve was leaking even though there was no PS fluid coming from the vacuum lines we thought the valve itself may be leaking and plus the new pump came with the valve hole pre-plugged with a bolt so we blocked off the vacuum lines and did away with the valve.

Question is I've noticed quite a big difference in steering stiffness especially in parking lots & at low speeds since we did away with the valve and replaced the pump. Anyone else have experience with or without the valve? Does it make that much difference in steering effort? I kinda liked the one-finger effort my LS used to have.......
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Old 11-08-10, 04:52 PM   #2
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I think the only way to be sure would be to steer someone else's LS that has had the valve removed. I installed a new idle up valve in mine, rather than remove it, so I can't tell you. However, I've heard some people say that the difference is nominal. If you want to rule out other causes, you could check the solenoid valve to make sure it's completely clean (in case changing the pump caused some dirt to get in there) and if you eliminate that, you can do some further diagnostics as I described in this thread:

http://www.clublexus.com/forums/ls40...-steering.html

It is possible that the solenoid was somewhat dirty to begin with but did not present a problem with the ACV valve installed (as it caused the pump to run faster, thereby creating higher pressure). Now that there is a decrease in pressure from not having the ACV valve installed, the dirt may be more of an issue. If that's the case, then cleaning the solenoid valve may help.

Last edited by 91LS400vgb; 11-08-10 at 04:52 PM.. Reason: typo
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Old 11-09-10, 03:19 AM   #3
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Thanks 91LS
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Old 11-09-10, 12:45 PM   #4
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Stevie, I plugged mine with a bolt when doing the timing belt. I completely agree with you. The steering feel is much stiffer than before. In fact, I did not tell my wife about it. It is her daily driver. The first thing she said to me was that the steering is much stiffer. On my LS the change was not nominal, but significant. I kept all the parts and may put them back on at some point. I think my PS leak was the tiny O-ring on the bottom of the reservoir.
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Old 11-09-10, 01:59 PM   #5
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I too just replaced pump (used), high pressure hose (new) and rack (rebuild), and noticed stiffness in steering. I did poured in power steering fluid instead of ATF, so I am not sure if that is the cause. But will be draining and replacing with ATF this weekend.

Prior to replacement my rack has been leaking for a while, and I have topped off with power steering fluid (not ATF), and steering was light. So not sure if stiffness came from using non-recommended fluid. But will go with factory recommended fluid since I just replaced everything.

BTW, the main leak was in the high pressure hose. I replaced the rack/pump because that was what dealer had recommended when I first noticed leaks (they wanted $ 2000+). Ended up just paying $400 for parts and $150 for labor.
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Old 11-10-10, 08:08 AM   #6
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Great info everyone.

WHen I bough my '93 last spring the pump had been leaking (as diagnosed from Lexus) along with a slight leak in the rack for about 4 years or 40-50,000km but the steering was light as a feather.

I replaced the high pressure line and topped up the system with Lucas stop leak just after buying the car. I immediately noticed stiffer steering. As time went by it became a little easier.

Then last weekend after about 6 months of ownership we replaced the pump & resovoir & removed the ACV valve and plugged the vacuum lines and filled up with Lucas PS fluid. Now the steering is twice as stiff. For example if I'm in the city around stop lights and turn a corner I can't just let go of the wheel to have the car return to straight after making a corner - I have to force it back (with reasonable effort) or it will remain steering around the corner......

It does get a bit easier as the car warms up.......

Sounds like I have a few options:

Flush & refill with ATF (is that the recommended fluid from Lexus? I have no manual)

Clean the solenoid screen

Replace the ACV with a new one and replace the vacuum lines (which I kept)

Live with it - it;'s not leaking
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Old 11-10-10, 01:59 PM   #7
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Quote:
Originally Posted by StevieA View Post
......

It does get a bit easier as the car warms up.......

Sounds like I have a few options:

Flush & refill with ATF (is that the recommended fluid from Lexus? I have no manual)
.....
Yes, Lexus recommends Dexron ATF - I recommend Mobil 1 Synthetic ATF, which meets and exceeds the Dexron requirements. Good luck, Steve. Keep us updated.
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Old 11-21-10, 09:28 AM   #8
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Well, my wonderful "steal" of a deal of a brand new pump for $149 off Ebay just blew a snap ring from the metal groove due to poor manufacturing/cheap product so tomorrow when I get it repaird we'll refill with Dexron III & I'll report on how it effected the steering effort. I'm expecting it will lighten it.
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Old 11-21-10, 01:48 PM   #9
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I plugged my idle up valve and noticed no difference whatsoever. I believe the idle up valve only increases the rpm of the engine when under certain steering conditions the idle decreases. ( like cold wather in a parking lot)
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Old 11-22-10, 01:05 PM   #10
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So as I posted we had to regroove a slot for the snap ring to fit into to seal the pressure valve. We re-grooved it a bit lower in the shaft making the spring compress more and re-filled with Dexron III ATF. Had some issues since because I think all the shavings from the machine work weren't flushed from the pump and they lodged the pressure valve and I had NO power steering a few times however they seemed to have worked themselves free because now when I have power steering its as easy as ever - one finger type effort - so I have to agree the ACV valve doesn't appear to have a large effect on steering effort because mine is removed and plugged.
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Old 11-27-10, 06:53 PM   #11
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From looking at the valve here is how I think it works. There is a cylinder with a spring behind it. this cylinder's face is exposed to pump pressure. As the pump pressure increases (cold weather, lock steering, steep hill ect.) the piston moves connecting the vacuum hose that is before the throttle plate to the vacuum hose that is after the throttle plate. This in turn does the same as slightly opening the throttle therefore increasing the rpms of the engine. The higher the pressure the more the piston moves the more air it allows to go thought the vacuumm hoses the higher the "throttle opening" is. By the calibration of the spring behind the piston the correct amount of throottle per power steering pump pressure is dialed in. If this analysis is correct than the only times you should see a difference when you do not have an idle up valve (because you plugged it) is during the afore mentioned conditions which are rather infrequent. (especially for me because it does not get cold here and there are not many steep hills plus a usually do not hit the steering stops. I also run my tires at 34 psi so less friction during parking lot manuevering
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Old 12-02-10, 02:00 PM   #12
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Quote:
Originally Posted by StevieA View Post
So as I posted we had to regroove a slot for the snap ring to fit into to seal the pressure valve. We re-grooved it a bit lower in the shaft making the spring compress more and re-filled with Dexron III ATF. Had some issues since because I think all the shavings from the machine work weren't flushed from the pump and they lodged the pressure valve and I had NO power steering a few times however they seemed to have worked themselves free because now when I have power steering its as easy as ever - one finger type effort - so I have to agree the ACV valve doesn't appear to have a large effect on steering effort because mine is removed and plugged.
Great update Stevie! I need to mention that I filled mine back up with PS Fluid and not ATF, so my stiff steering does now sound like the fluid. I guess I will do a flush and fill... http://www.lexls.com/tutorials/steering/psflush.html

Last edited by smamas; 12-02-10 at 02:04 PM..
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Old 12-03-10, 06:43 AM   #13
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Originally Posted by smamas View Post
Great update Stevie! I need to mention that I filled mine back up with PS Fluid and not ATF, so my stiff steering does now sound like the fluid. I guess I will do a flush and fill... http://www.lexls.com/tutorials/steering/psflush.html
Yes that should do it. But you know, to re-fill the system after we repaired the pump it only took about a liter of ATF - but that was enough to make a HUGE difference in steering effort (as opposed to PS fliud or stop leak) - not sure what the whole system holds......
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Old 12-16-10, 11:51 AM   #14
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Quote:
Originally Posted by StevieA View Post
Yes that should do it. But you know, to re-fill the system after we repaired the pump it only took about a liter of ATF - but that was enough to make a HUGE difference in steering effort (as opposed to PS fliud or stop leak) - not sure what the whole system holds......
Guys, just wanted to update this thread, that replacing the PS Fluid with ATF fixed my stiff steering. I did the PS Flush and added just about a quart and a half of Dexron, and the steering turns like a dream again! I had some guy tell me that the only difference between PS Fluid and Trans fluid, was the color....obviously not the case when it comes to Lexus PS pumps!
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Old 12-16-10, 12:02 PM   #15
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i removed the valve, cleaned the solenoid gauze and flushed/replaced the fluid with ATF - steering still nice and light here. Every once in a while when i'm turning at a hot/slow idle the steering will weight up but its never a problem
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Old 12-16-10, 12:02 PM
 
 
 
 
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400, 93, acv, club, fluid, idle, leaking, lexus, lower, ls, ls400, power, pressure, steering, valve

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