SC300 Power Steering problems (Replaced nearly everything, please help!!!)
02-06-21, 12:18 AM
#1
Driver School Candidate
Thread Starter
SC300 Power Steering problems (Replaced nearly everything, please help!!!)
Hey guys,
I've got a 94 SC300 5MT with about 220k on the clock. Pretty high miles, but overall well taken of car.
My last SC was a 97 Auto, and the power steering in that car worked flawlessly, so I do recall what a properly working system is supposed to be like.
Here's the thing....I've been FIGHTING the power steering in this car. I've not been able to get it to be 100% since day 1 of ownership back in October of 2020.
The previous owner has disclosed he had a whine with the power steering, and I felt pretty confident I would be able to tackle it, since I'm pretty well aware of the common PS issues these cars typically have.
I have replaced nearly every single component possible in the PS system. Here are my following of my attempts to chase down the problem(s).
- My first attempt was getting rid of the factory high pressure feed line, and converted that over to -6AN hoses, as that was a common leakage problem. I have also replaced all the soft hoses in the return lines, PS cooler, and eliminated the idle-up vacuum valve. I also added a Magnefine inline filter on the bottom of the PS cooler return loop.
- My second attempt, I have tried 2 different used PS pumps. That didn't solve the problem, and the whining/shuddering/hard steering is still there
- My third attempt, I've tried washing and cleaning the PS reservoir screen, replaced the Reservoir o-ring, and dropped the steering rack the first time and washed the PPS solenoid screen. No luck here.
- Then, I decided to replace the original steering rack, as I discovered some oil seepage past the inner tie rod boots. I've purchased a Reman OEM rack from Longo Lexus. Still whines/shudder, didn't solve it.
- Then, I've decided to use a Mityvac hand pump tester. I've pinched off the High pressure side hose, and pressurized it from the return line, to see if I can find any pressure drops that would indicate a hard line leak. I went up to about 20 psi here only, as it is the return side. Pressure held solid, no signs of it dropping.
- Then I've tried 2 different BNIB OEM Toyota PS pumps from Toyota. I've even put together a PS pressure tester tool, with a shut off valve with a 2000 psi gauge for testing.
All testing have been done on BNIB pump #1.
I followed the TSRM diagnosis instructions, and tested the pump with the valve fully shut with the engine running at idle, and it comes up to right about 1140 psi +/- which is the minimum pressure of what Toyota wants to see.
Test 1 at idle speed, Toyota wants to see a min of 1140 psi with the valve fully shut.
Test 2, with the steering position locked to lock at either position with the valve open, Toyota also wants to see a min pressure of 1140 psi. If either side of the full lock shows a significant value different than the other, or low, then one of the possible cause is a bad rack seal.
Links to the videos of the pressure tests I've done. For those who are curious about what the value looks like, here are the links to the clips below. You can also hear the whining/shuddering in these vids below.
Idle test
/
Turning lock to lock test
At this point, I'm lost. How can the pump be within spec, and have the symptoms that it has now??? Unless it was bad tolerances in the vane plates set from factory???
Usually a OEM part have a much stricter QA/QC then aftermarket, and the chances of something like that happen with a OEM is not impossible, but very very unlikely.
But just in case, I've reached out to my parts guy, and discussed about taking it apart to rebuild my self. But then all the OEM Toyota vane plates are discontinued??
I started to wonder if I had a bad pump, and then replaced it with another BNIB OEM Toyota pump.
The whining/high steering effort is still there, but the shuddering is gone. For a moment, I thought I was heading in the right direction, but no matter how long I've drove the car, the whining seems to come back progressively worst and worst. Especially when the fluid temps are hotter. I've tried Redline D4 ATF, Redline high temp ATF, and back to Toyota Type TIV, with no difference on all these 3 fluids.
Then I wondered if there was anything potentially wrong with the rebuild of the reman rack?? Even if the pressure comes up to spec on the PS tester at full lock, the TSRM states that if there is even ANY a slightest amount of scratch on the rack during the rebuild, this can cause a potential fluid/air leak as the rack travels past the seals on it's way to full lock.
I decided to take the reman rack off, and pulled the tie rods boot back, and here's what I found.
(BE WEARY OF REMAN RACKS, PLEASE DOUBLE CHECK FOR THESE BEFORE INSTALLING REMANS ON YOUR CAR!)
Upon finding this scratch, I decided to run my finger nail through this. It is very slight, but it does catch my fingernail. Then I decided to throw on my spare Mkiv Supra rack that has probably about 5k miles on it. That one was not a rebuild. It is brand new, and worked flawlessly on my Supra, so I know there's nothing wrong with that one. So I proceeded to having it installed just for testing, and then.....
The whining/high steering effort at stationary is still there....... Well *****!!....
At this point, I'm completely burned out. The only thing left in the car I have not replaced, is the factory hard lines, and factory PS cooler lines.
Those were tested with my Mityvac and weren't leaking. Unless there was a restriction, I can't think of anything else at this point.
When I run the car with the reservoir cap off, it looks it's getting a constant supply of fluid to the pump, and the level stays pretty constant while it's running. No bubbles after bleeding.
If anyone has any idea, of know of something that I don't, please chime in. I would appreciate any help at this point. I've tried just about everything I could think of, and I am just completely defeated.
I've burned tons of money between those OEM parts, and done more alignments than I would've liked between pulling parts off every now and then for testing.
I really would like to accurately pinpoint for my next approach for chasing this down, before just throwing more money at it.
FWIW, my front wheels are 9.5in wide, 255/30/19 tires up front, and running about 7.5 degrees of caster, and about 35psi of tire pressure.
My Supra runs a 10.5 up front, 295/30/18 at 10 degrees of caster, but my PS system in that car works much better than this one without *****ing
Thanks for looking
I've got a 94 SC300 5MT with about 220k on the clock. Pretty high miles, but overall well taken of car.
My last SC was a 97 Auto, and the power steering in that car worked flawlessly, so I do recall what a properly working system is supposed to be like.
Here's the thing....I've been FIGHTING the power steering in this car. I've not been able to get it to be 100% since day 1 of ownership back in October of 2020.
The previous owner has disclosed he had a whine with the power steering, and I felt pretty confident I would be able to tackle it, since I'm pretty well aware of the common PS issues these cars typically have.
I have replaced nearly every single component possible in the PS system. Here are my following of my attempts to chase down the problem(s).
- My first attempt was getting rid of the factory high pressure feed line, and converted that over to -6AN hoses, as that was a common leakage problem. I have also replaced all the soft hoses in the return lines, PS cooler, and eliminated the idle-up vacuum valve. I also added a Magnefine inline filter on the bottom of the PS cooler return loop.
- My second attempt, I have tried 2 different used PS pumps. That didn't solve the problem, and the whining/shuddering/hard steering is still there
- My third attempt, I've tried washing and cleaning the PS reservoir screen, replaced the Reservoir o-ring, and dropped the steering rack the first time and washed the PPS solenoid screen. No luck here.
- Then, I decided to replace the original steering rack, as I discovered some oil seepage past the inner tie rod boots. I've purchased a Reman OEM rack from Longo Lexus. Still whines/shudder, didn't solve it.
- Then, I've decided to use a Mityvac hand pump tester. I've pinched off the High pressure side hose, and pressurized it from the return line, to see if I can find any pressure drops that would indicate a hard line leak. I went up to about 20 psi here only, as it is the return side. Pressure held solid, no signs of it dropping.
- Then I've tried 2 different BNIB OEM Toyota PS pumps from Toyota. I've even put together a PS pressure tester tool, with a shut off valve with a 2000 psi gauge for testing.
All testing have been done on BNIB pump #1.
I followed the TSRM diagnosis instructions, and tested the pump with the valve fully shut with the engine running at idle, and it comes up to right about 1140 psi +/- which is the minimum pressure of what Toyota wants to see.
Test 1 at idle speed, Toyota wants to see a min of 1140 psi with the valve fully shut.
Test 2, with the steering position locked to lock at either position with the valve open, Toyota also wants to see a min pressure of 1140 psi. If either side of the full lock shows a significant value different than the other, or low, then one of the possible cause is a bad rack seal.
Links to the videos of the pressure tests I've done. For those who are curious about what the value looks like, here are the links to the clips below. You can also hear the whining/shuddering in these vids below.
Idle test
Turning lock to lock test
At this point, I'm lost. How can the pump be within spec, and have the symptoms that it has now??? Unless it was bad tolerances in the vane plates set from factory???
Usually a OEM part have a much stricter QA/QC then aftermarket, and the chances of something like that happen with a OEM is not impossible, but very very unlikely.
But just in case, I've reached out to my parts guy, and discussed about taking it apart to rebuild my self. But then all the OEM Toyota vane plates are discontinued??
I started to wonder if I had a bad pump, and then replaced it with another BNIB OEM Toyota pump.
The whining/high steering effort is still there, but the shuddering is gone. For a moment, I thought I was heading in the right direction, but no matter how long I've drove the car, the whining seems to come back progressively worst and worst. Especially when the fluid temps are hotter. I've tried Redline D4 ATF, Redline high temp ATF, and back to Toyota Type TIV, with no difference on all these 3 fluids.
Then I wondered if there was anything potentially wrong with the rebuild of the reman rack?? Even if the pressure comes up to spec on the PS tester at full lock, the TSRM states that if there is even ANY a slightest amount of scratch on the rack during the rebuild, this can cause a potential fluid/air leak as the rack travels past the seals on it's way to full lock.
I decided to take the reman rack off, and pulled the tie rods boot back, and here's what I found.
(BE WEARY OF REMAN RACKS, PLEASE DOUBLE CHECK FOR THESE BEFORE INSTALLING REMANS ON YOUR CAR!)
Upon finding this scratch, I decided to run my finger nail through this. It is very slight, but it does catch my fingernail. Then I decided to throw on my spare Mkiv Supra rack that has probably about 5k miles on it. That one was not a rebuild. It is brand new, and worked flawlessly on my Supra, so I know there's nothing wrong with that one. So I proceeded to having it installed just for testing, and then.....
The whining/high steering effort at stationary is still there....... Well *****!!....
At this point, I'm completely burned out. The only thing left in the car I have not replaced, is the factory hard lines, and factory PS cooler lines.
Those were tested with my Mityvac and weren't leaking. Unless there was a restriction, I can't think of anything else at this point.
When I run the car with the reservoir cap off, it looks it's getting a constant supply of fluid to the pump, and the level stays pretty constant while it's running. No bubbles after bleeding.
If anyone has any idea, of know of something that I don't, please chime in. I would appreciate any help at this point. I've tried just about everything I could think of, and I am just completely defeated.
I've burned tons of money between those OEM parts, and done more alignments than I would've liked between pulling parts off every now and then for testing.
I really would like to accurately pinpoint for my next approach for chasing this down, before just throwing more money at it.
FWIW, my front wheels are 9.5in wide, 255/30/19 tires up front, and running about 7.5 degrees of caster, and about 35psi of tire pressure.
My Supra runs a 10.5 up front, 295/30/18 at 10 degrees of caster, but my PS system in that car works much better than this one without *****ing
Thanks for looking
Last edited by BoostWang; 02-06-21 at 12:44 AM.
02-06-21, 07:06 AM
#2
That is impressively thorough.
"Those were tested with my Mityvac and weren't leaking. Unless there was a restriction..."
A restriction somewhere in the system (most likely the cooler, at this point) was my only thought right up till the end. That would explain the pump testing okay for pressure but the rack still whining, as well as the system having no leaks with those symptoms, but I'm not sure whether the lack of circulation would be obvious from a visual inspection of the reservoir.
"Those were tested with my Mityvac and weren't leaking. Unless there was a restriction..."
A restriction somewhere in the system (most likely the cooler, at this point) was my only thought right up till the end. That would explain the pump testing okay for pressure but the rack still whining, as well as the system having no leaks with those symptoms, but I'm not sure whether the lack of circulation would be obvious from a visual inspection of the reservoir.
02-06-21, 02:50 PM
#3
This isn't much help but my SC300 shudders when turning to the left at low speeds as well. I've replaced bushings and LCA bushings. Only thing I haven't changed is inner tie rods. Can't really help but it's annoying. Does it do it when the front wheels are up or only when there's resistance?
02-06-21, 04:59 PM
#4
Driver School Candidate
Thread Starter
That is impressively thorough.
"Those were tested with my Mityvac and weren't leaking. Unless there was a restriction..."
A restriction somewhere in the system (most likely the cooler, at this point) was my only thought right up till the end. That would explain the pump testing okay for pressure but the rack still whining, as well as the system having no leaks with those symptoms, but I'm not sure whether the lack of circulation would be obvious from a visual inspection of the reservoir.
"Those were tested with my Mityvac and weren't leaking. Unless there was a restriction..."
A restriction somewhere in the system (most likely the cooler, at this point) was my only thought right up till the end. That would explain the pump testing okay for pressure but the rack still whining, as well as the system having no leaks with those symptoms, but I'm not sure whether the lack of circulation would be obvious from a visual inspection of the reservoir.
I'm looking into picking up a set of hard lines off a 98 as we speak. But in theory, if the fluid level remains at the top of the reservoir, then the pump isn't drawing in fluid faster than what the return can supply right?
I'll still replace the lines anyways. Last desperate measures at this point.
This isn't much help but my SC300 shudders when turning to the left at low speeds as well. I've replaced bushings and LCA bushings. Only thing I haven't changed is inner tie rods. Can't really help but it's annoying. Does it do it when the front wheels are up or only when there's resistance?
Mine was consistently shuddering on left turns, and occasionally on the right. Whines the most under the lowest speeds and while sitting which is at it's highest load.
After swapping to the second pump, the shuddering is gone, but I'm still getting a constant whine and heavy steering under load speeds/sitting.
02-06-21, 07:57 PM
#5
As a side note, I think 400s have full (dynamic depending on speed) assisted power steering and the 300s (at least the 5-speeds) did not. I remember the difference between the 400 and my 300 for sure. There's even an unused plug on my steering rack that has no connector on the car side.
02-06-21, 11:17 PM
#6
Driver School Candidate
Thread Starter
As a side note, I think 400s have full (dynamic depending on speed) assisted power steering and the 300s (at least the 5-speeds) did not. I remember the difference between the 400 and my 300 for sure. There's even an unused plug on my steering rack that has no connector on the car side.
I'm not familiar with the 400s, but if memory serves some of the late model 2jz powered sedans had their PPS solenoid on the high pressure outlet of the PS pump, instead of being on the racks themselves.
They were at least on the GS and Aristos. Can't remember if they were on IS' or not.
If anyone has a spare clean set of PS hardlines from a 97+ and up, hmu!
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02-10-21, 12:01 AM
#8
Driver School Candidate
Thread Starter
**Update**
I swapped the PS from my Supra into this car, and no matter how much I try to bleed the system, the whine and hard steering effort is all still there. The pump works perfectly fine on the Supra, and I know the rack is good. So the factory PS cooler and hard lines are the next suspect. I'm looking to purchase a set of lines, so here's my WTB ad. Thanks for looking
https://www.clublexus.com/forums/market/961351
I swapped the PS from my Supra into this car, and no matter how much I try to bleed the system, the whine and hard steering effort is all still there. The pump works perfectly fine on the Supra, and I know the rack is good. So the factory PS cooler and hard lines are the next suspect. I'm looking to purchase a set of lines, so here's my WTB ad. Thanks for looking
https://www.clublexus.com/forums/market/961351
03-23-21, 02:30 PM
#9
Driver School Candidate
Thread Starter
**Update**
Replaced the factory PS cooler from another car. Symptoms have significantly improved. Finally, I've got a lead towards a solution
Picked up a 97 cooler, because the loops are routed differently to fit better with the 97+ bumpers. Compared the part #'s, and they were different from early gen cars.
I believe there was blockage(s) that is causing aeration of the fluid while running, even though there is no leaks and pressure tested.
Perhaps someone may have attempted a leak fix using something like "Stop-leak" at one point.
Now I'm looking to replace the last 2 metal return lines that is bolted to the engine bay. My wanted ad is listed here
https://www.clublexus.com/forums/market/961351
Let me know as I'm looking to purchase asap.
Thanks
Replaced the factory PS cooler from another car. Symptoms have significantly improved. Finally, I've got a lead towards a solution
Picked up a 97 cooler, because the loops are routed differently to fit better with the 97+ bumpers. Compared the part #'s, and they were different from early gen cars.
I believe there was blockage(s) that is causing aeration of the fluid while running, even though there is no leaks and pressure tested.
Perhaps someone may have attempted a leak fix using something like "Stop-leak" at one point.
Now I'm looking to replace the last 2 metal return lines that is bolted to the engine bay. My wanted ad is listed here
https://www.clublexus.com/forums/market/961351
Let me know as I'm looking to purchase asap.
Thanks
Last edited by BoostWang; 03-23-21 at 02:34 PM.
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