Power steering -- Low flow/pressure issue
05-08-10, 10:53 PM
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Power steering -- Low flow/pressure issue
I've lurked and searched, done some stuff and now this. What to do when flow control valve gets stuck in the pump? OR, what is causing the flow control valve to get stuck in the pump?
Complete PS history as I know it, since I've had it:
1993 LS400 with around 167K (miles) on the odo.
mid 2008: had a leak repaired on rack-end of pressure hose. (hint: pressure hose repairs are very economical if you can find this service and it is done right)
late 2009: replaced return hose at reservoir as it was turning brittle (didn't leak yet)
early 2010: pinhole leak on pump end of pressure hose spayed fine mist all over pump, leading me to believe pump seals were going, so bought seal kit and bearing and rebuilt my pump, reinstalled and discovered said leak in the hose. Had same hose-repair guy fix pump-end of hose, he mentioned he was careful about re-installing the in-line restrictor/regulator or whatever it is that is crimped mid-section into that end of the pressure hose. Deleted vaccuum-assist valve thingy with metric bolt and thin app of silicone on the threads and rubber caps on the intake.
Here's what I found when I rebuilt my pump: I was not the first one to do so. I looked all over for the screen in the reservoir (mentioned in various tutorials and stickies) and there is NO screen in my reservoir. However, I did have a tiny screen on the flow control valve itself, which had a nice collection of grit on it, which I cleaned up. If you don't already know about this screen, look for it next time you are in your pump (perhaps it is certain models, there are 6 different types of valves to choose from should you have to buy a new valve). VERY IMPORTANT DETAIL: the previous genius who had it apart had the flow control valve in either a vise or a pair of pliers at some point, causing teeth marks and tiny ridges on it. Not good.
Anyways, I didn't want to mess anymore with the valve, so I stuck it back in as is. It worked before, right? Maybe...
When I put it all back together, and bled the system, I had power steering for about a minute, and it went away before I could get my wheels back on the ground. Drove around for a week with no PS and took my pump back out the next weekend to have a look-see, as I recalled the ridges on the flow control valve. The valve was STUCK, in the by-pass/dump position all the way back with the spring fully compressed. I had a talk with my wife's brother-in-law (used to rebuild trannys for a living, knows a thing or two about hydraulic valves) and he (and another mechanic I know) suggested I file off the ridge marks with some fine emery cloth, so I did, and put everything back together. Same deal. Worked for about a minute and then nada.
So I did more lurking and more reading, removed the rack solenoid to clean the screen and what's this? NO SCREEN ON THE SOLENOID. No good. There were teeth marks on the solenoid nut, I suppose the same genius had been in there too. Anyways, what am I to do but clean the solenoid with brake cleaner and slap it back on sans screen. Took the pump out a 3rd time, valve is stuck again, emery-clothed the ridges a bit more just to feel good, and slapped it back in. Flushed the fluid this time with a brand-name Mercon/Dex product. Noticed while flushing, some black crud came out, and the flow seemed to be not really all that great, a little more than a trickle. Aren't these suppose to be high pressure/high flow systems? Bled the system, and again, worked for about a minute, and then... that valve must be stuck again, but 3 times a charm and I have not taken it apart since.
Of note... there is definitely flow. I could see the air bubbles in the reservoir when I bled the system. The flow seems much lower than when it worked: you could hear the flow in the reservoir and see the fluid swirling a bit before, but now the swirling is gone, and the sound of the flow is 'quieter'. The pump is QUIET, I can no longer hear the sound of the vanes turning in the pump housing, and no noise occurs on lock-to lock, which I am attributing to the flow-control valve being stuck in the lock-to-lock position.
Last weekend I took the rack solenoid back out and hot-wired it to the battery for a couple of seconds, and it does work. I also ran an ohm meter on it and it is good according to the "Power steering bible". Also ran a volt meter on the wires with engine running and it shows around 7-9 volts (which I am assuming is good, since the PS computer steps the voltage down, right? PS bible mentions not leaving it on 12V for very long or it burns out...) I am assuming the solenoid is doing its job, even if it is missing its screen. Bled the system again and knew there was flow because air bubble in the reservoir, but same deal, still low flow, still no power steering.
All I can think of that is happening is that something must be blocking one of the lines. I want to take a compressor and try to blow them out. Going back to the pressure line re-build, is it possible to install that in-line restrictor/regulator thingy crimped into the line backwards? Is it one way or uni-directional?
So, I am tired of pulling the pump out now on a regular basis, and do not want to do so without any more info. Has anyone ran into a stuck flow-control valve before? I'm coming up dry searching that subject. I am convinced something is causing a pressure build up in the system, pushing that valve all the way back to where it's not supposed to go, and am more interested in solving the cause of the problem before considering a new pump with a valve that does not stick.
I don't have too much of a problem with it, but my wife is almost not physically capable of parking this thing without power steering, so it means she doesn't get to drive it much anymore...
Any thoughts? Thanks in advance...
Ben
Complete PS history as I know it, since I've had it:
1993 LS400 with around 167K (miles) on the odo.
mid 2008: had a leak repaired on rack-end of pressure hose. (hint: pressure hose repairs are very economical if you can find this service and it is done right)
late 2009: replaced return hose at reservoir as it was turning brittle (didn't leak yet)
early 2010: pinhole leak on pump end of pressure hose spayed fine mist all over pump, leading me to believe pump seals were going, so bought seal kit and bearing and rebuilt my pump, reinstalled and discovered said leak in the hose. Had same hose-repair guy fix pump-end of hose, he mentioned he was careful about re-installing the in-line restrictor/regulator or whatever it is that is crimped mid-section into that end of the pressure hose. Deleted vaccuum-assist valve thingy with metric bolt and thin app of silicone on the threads and rubber caps on the intake.
Here's what I found when I rebuilt my pump: I was not the first one to do so. I looked all over for the screen in the reservoir (mentioned in various tutorials and stickies) and there is NO screen in my reservoir. However, I did have a tiny screen on the flow control valve itself, which had a nice collection of grit on it, which I cleaned up. If you don't already know about this screen, look for it next time you are in your pump (perhaps it is certain models, there are 6 different types of valves to choose from should you have to buy a new valve). VERY IMPORTANT DETAIL: the previous genius who had it apart had the flow control valve in either a vise or a pair of pliers at some point, causing teeth marks and tiny ridges on it. Not good.
Anyways, I didn't want to mess anymore with the valve, so I stuck it back in as is. It worked before, right? Maybe...When I put it all back together, and bled the system, I had power steering for about a minute, and it went away before I could get my wheels back on the ground. Drove around for a week with no PS and took my pump back out the next weekend to have a look-see, as I recalled the ridges on the flow control valve. The valve was STUCK, in the by-pass/dump position all the way back with the spring fully compressed. I had a talk with my wife's brother-in-law (used to rebuild trannys for a living, knows a thing or two about hydraulic valves) and he (and another mechanic I know) suggested I file off the ridge marks with some fine emery cloth, so I did, and put everything back together. Same deal. Worked for about a minute and then nada.
So I did more lurking and more reading, removed the rack solenoid to clean the screen and what's this? NO SCREEN ON THE SOLENOID. No good.
There were teeth marks on the solenoid nut, I suppose the same genius had been in there too. Anyways, what am I to do but clean the solenoid with brake cleaner and slap it back on sans screen. Took the pump out a 3rd time, valve is stuck again, emery-clothed the ridges a bit more just to feel good, and slapped it back in. Flushed the fluid this time with a brand-name Mercon/Dex product. Noticed while flushing, some black crud came out, and the flow seemed to be not really all that great, a little more than a trickle. Aren't these suppose to be high pressure/high flow systems? Bled the system, and again, worked for about a minute, and then... that valve must be stuck again, but 3 times a charm and I have not taken it apart since.Of note... there is definitely flow. I could see the air bubbles in the reservoir when I bled the system. The flow seems much lower than when it worked: you could hear the flow in the reservoir and see the fluid swirling a bit before, but now the swirling is gone, and the sound of the flow is 'quieter'. The pump is QUIET, I can no longer hear the sound of the vanes turning in the pump housing, and no noise occurs on lock-to lock, which I am attributing to the flow-control valve being stuck in the lock-to-lock position.
Last weekend I took the rack solenoid back out and hot-wired it to the battery for a couple of seconds, and it does work. I also ran an ohm meter on it and it is good according to the "Power steering bible". Also ran a volt meter on the wires with engine running and it shows around 7-9 volts (which I am assuming is good, since the PS computer steps the voltage down, right? PS bible mentions not leaving it on 12V for very long or it burns out...) I am assuming the solenoid is doing its job, even if it is missing its screen. Bled the system again and knew there was flow because air bubble in the reservoir, but same deal, still low flow, still no power steering.
All I can think of that is happening is that something must be blocking one of the lines. I want to take a compressor and try to blow them out. Going back to the pressure line re-build, is it possible to install that in-line restrictor/regulator thingy crimped into the line backwards? Is it one way or uni-directional?
So, I am tired of pulling the pump out now on a regular basis, and do not want to do so without any more info. Has anyone ran into a stuck flow-control valve before? I'm coming up dry searching that subject. I am convinced something is causing a pressure build up in the system, pushing that valve all the way back to where it's not supposed to go, and am more interested in solving the cause of the problem before considering a new pump with a valve that does not stick.
I don't have too much of a problem with it, but my wife is almost not physically capable of parking this thing without power steering, so it means she doesn't get to drive it much anymore...
Any thoughts? Thanks in advance...
Ben
05-09-10, 07:58 AM
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take off the reservoir .... and soak it in purple power or something like that i also couldnt see the screen but as i cleaned it i could see particles coming out,,, what happens just like a transmission or engine with a pickup screen or filter the filter gets clogged and then when the pressure builds up all the junk blocks the filter and doesnt allow any fluid through so then it "starves" the system worth a try right ? worked on my sc4 GOODLUCK
05-09-10, 08:26 AM
#3
My solenoid didn't have the screen also. The solenoid worked but after a while would freeze up. Probably from all of the grit and crap that got down in it. I cleaned the valve as much as I possibly could and it would for a day or two then get really tight again. I ended up replacing the entire rack with a good used part since you can't buy just the solenoid from Toyota. It's part of the PPS valve. It's been work great ever since. I think I paid around $190 shipped for the rack, can't complain there. Better than pulling my hair out trying to fix a broken part.
05-09-10, 09:50 AM
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take off the reservoir .... and soak it in purple power or something like that i also couldnt see the screen but as i cleaned it i could see particles coming out,,, what happens just like a transmission or engine with a pickup screen or filter the filter gets clogged and then when the pressure builds up all the junk blocks the filter and doesnt allow any fluid through so then it "starves" the system worth a try right ? worked on my sc4 GOODLUCK
Ben
05-09-10, 10:05 AM
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My solenoid didn't have the screen also. The solenoid worked but after a while would freeze up. Probably from all of the grit and crap that got down in it. I cleaned the valve as much as I possibly could and it would for a day or two then get really tight again. I ended up replacing the entire rack with a good used part since you can't buy just the solenoid from Toyota. It's part of the PPS valve. It's been work great ever since. I think I paid around $190 shipped for the rack, can't complain there. Better than pulling my hair out trying to fix a broken part.
I am still leaning towards some kind of blockage in the lines from when I did the flush, or a problem with the in-line pressure regulator crimpy thingy...
Ben
05-09-10, 10:25 AM
#6
too much reading...blockage test can be done by taking off the return line and holding it over the reservoir while its running,should be an even stream coming out of the line,if its spitting or inconsistant u may have a blockage issue in the line somewhere
05-09-10, 10:45 AM
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): I need to get into the pump and free up the suspected stuck valve first, right? Then do the above mentioned test?I should mention, every time I put the pump back together, I made sure the flow control valve was moving freely back and forth, full 360deg rotation of valve in all positions.
Ben
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05-09-10, 12:06 PM
#8
I HAVE to make a comment here. I got a new power steering pressure hose from RockAuto- Edelmann brand - for something like $57 delivered. Installation was a breeze. Doesn't make sense to repair an existing power steering hose if you can buy a new one for so cheap.
05-09-10, 08:24 PM
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here it is...
you could say...
I got hosed on that one.
Are you happy with the Edelmann hose?
Definitely good enough to last me the rest of the time I'll own the car.
05-09-10, 10:32 PM
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Thanks.
Ben
05-10-10, 09:16 PM
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so... am I to understand nobody else has experienced a condition where the flow control valve gets pushed back (due to back pressure? I don't know) in the pump and gets stuck there? ...don't mean to come across as impatient by bumping my own thread, I'm going in a trip in 2 weeks and hopefully it'll be with power steering. 
Ben
05-11-10, 05:59 PM
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no can do, would rather buy a re-built pump, which I am trying to avoid since I already rebuilt mine with new seals and bearing... If someone can price that valve better, I am all ears.Ben