I replaced the pump on my 97 LS 400 with an aftermarket reman unit. All was well until the temps dropped, when on cold mornings the pump would grind very loudly until it warmed. Assuming it was a faulty reman unit, I replace it (under part warranty). However, I still have the same symptoms. If the temp is below 40F, then it makes terrible noise, both at idle and with load. I self installed, so I am assuming it has to be an error I made, but I am lost as to what it could be. I have no leaks, and when warm it works w/o errors. Any ideas appreciated.
BTW - I read this site weekly - awesome Lexus stuff.

 

did you open up the reservoir and clean it out? sounds like you have crap in there blocking the pickup when the fluid thickens up.

 

Thanks for the suggestion. Turns out the screen appeared to be clogged, and when I cleaned it a bunch of crap came out. However, the pump sounds even worse now (noise maintains even when warm). I really can't believe a power steering pump is this much work. Anyway, I can't find someone who will work on an older Lexus (no dealer within 100 miles), so I will keep at it.

 

Check your PS fluid level. It will make noise if it is low.

 

Sounds like air is in the system. Is the fluid foamy?

 

Thankd everyone. No, the fluid level has always been good. Re: air in system - I haven't noticed foamy fluid, but I will make sure. I have suspected air in system (possibly where the high pressure side attaches to pump). Is there supposed to be a brass washer on the pump side of the fitting? My only other guess is that the reservor tank feed tube fits kind of loose in the pump (o-ring is still there). Really appreciate the ideas.
Note: just after I cleaned the screen, in my 60 degree garage, system worked perfect. Next morning, loud - and loud ever since, regardless of temp??

 

https://www.clublexus.com/forums/ls4...p-problem.html
Did you see this thread?

 

And now, without any intervention, this morning it is almost quiet..got to be air from somewhere..

 

How do you bleed the PS or just leave the cap open?

 

I just leave it open

 

Now, on a 25 degree morning, I had no noise whatsoever, but no power assist at all! I am about to replace the pump, rack, and lines - maybe thats what it will take. My symptoms are all over the place.

 

Sounds like the pump finally gave out.

 

Should not need to do all that. That will take care of it all but racks are usually last to go. Your not leaking fluid on the ground? If your pump is out, doing the lines and pump together would be smart. Otherwise, fix the leak then bleed the system by taking the cap off, engine running, and turning the wheels rack to rack as many as 15 - 25 times to get all the air out. Obviously, maintaining dextron 3 fluid level. Do this with the wheels off the ground. Not good on the front tires to do this on the ground. The rubber hose connecting the reservoir to the pump often needs replacing too.

 

Your power steering solenoid screen may need cleaning...

https://www.clublexus.com/forums/ls4...ystem-diy.html

 

Again, thanks for the input from fellow LS400 owners. Have to say I looked forward to owning one for a long time, for many reasons, one of which was its legendary reliability. I bought one with an amazing Lexus dealer service record...but this power steering issue has me about whipped.

I have been on/off of it for about 4 months now.
I replaced the pump yesterday, again. It is 50 degrees this morning, and I still have a mild growl. I have not replaced the lines because yet because I have no leaks, so I was confident that they were ok. I will try cleaning the solenoid screen soon.

Notes: I am using Castrol Des/Merc fluid. When I did the first replacement mid summer - it worked w/o issues until temps dropped. My 2nd replacement was when temps dropped, and it was only quiet on a very warm day - and I think I just pushed it to far - because it eventually lost all function. However, even on very warm days, I would notice slight loses in function at low rpms.

Obviously - my diagnostics could use some work....