Weird steering problems (not the lower shaft u-joint!) - Diagnosis help needed (1 Viewer)

[indridi]

Hello all,

I have a 2004 Prado 120 (= GX470 in the mechanics department) with some steering stiffness issues. It has 280k km on the clock (170k miles)

Since the lower steering shaft u-joint seems to be by far the most common known source of steering stiffness issues, I sort of blindly assumed that was it, and had it changed (new lower shaft with u-joint, original Toyota part). That didn't help, so I had to start thinking.

So I guess I'll need to describe what it's about:

• The following problems are only present when the car is warm, say after driving at least 15-20 minutes, the first 10-15 minutes, everything is normal.
• The following problems became considerably less pronounced after I changed the fluid (which, I must admit, probably hadn't been changed for ages, if at all).
• After fluid change, stiffness is less stiff, and becomes noticeable after a longer drive than before.
• I still have the old fluid, is there something there I could look for?
• Fluid level is normal.
• It is not leaking fluid.
• I have heard no weird noises when steering.
• Steering is normal when centered - driving straight on the highway, with the minimal 3-5 degree corrections of the steering, everything feels normal.
• Occasionally (but quite often), when rotating the steering more than one does on a straight road, the steering wheel comes into a "stiff region" - it doesn't block but for maybe 5 degrees of turning it is much stiffer so I need to apply maybe 3-5x the normal force to keep rotating it.
• If I keep turning the steering wheel for just a bit, it comes "out of" this stiffness region, and becomes smooth again.
• The same kind of stiffness over a limited, quite clearly defined "region of stiffness" can be felt when going back, i.e. when return the steering wheel to the central position.
• This can be felt at maybe 15 degrees of turning, e.g. for a fairly normal (non-violent) turn on a curvy highway at 90km/h or 60mph
• I tried revving the engine whilst in the "stiff region", I couldn't feel that it made a difference.

I asked at the local Toyota dealerships mechanical shop, but the mechanics there weren't sure what this was, and wanted to get the car in for some research (mech hours over here are ridiculously expensive so I'm trying som...).
Obviously, one suspects that the steering rack is simply shot. However, the lack of sounds, and the fact that everything is ok when cold apparently doesn't fit with the most usual symptoms of shot steering rack, which, so they say, are usually more pronounced when cold. Also, these steering racks are apparently indestructible.

Does this issue sound familiar to anyone?

Greetings,
Indriði

 

[Rednexus]

Were there any metal shavings in your old fluid? The racks on the 120 are actually kind of weak. You could have an internal issue in the steering rack making it hard to turn, and metal shavings in the fluid would be a telltale sign of that. The racks are not terribly expensive but do take several hours to install and remove. My rack was worn out at 150K, with the bushings being shot and the fluid was full of metal flakes (although I didn't have the hard steering issue you had).

 

[aztoytec]

I would try and flush the power steering fluid again, maybe a couple times. Might have some debris in the pump. If it was the rack I’d think it would do it all the time

 

[indridi]

Thanks @aztoytec and @Rednexus.

I got a reasonable price on a new rack, but a fuzzy estimation of "quite some amount of hours" of replacing it. Used to do this stuff myself, but lost access to the shop where I could do it.

Before I buy a new rack and have it replaced, I'll: filter the fluid and see what I find. And flush the rack once or twice more.

There was also talk (somewhere on the internet) of a filter in the reservoir, where some debris might sit.

Greetings,
Indriði

 

[Rednexus]

I did my own rack as a DIY and it took around 8 hours. I also spent several hours messing with other things and getting a new power steering line. For an experienced mechanic with a lift, it would probably be a 4 hour job. You will also need an alignment after the rack is installed.

At 18 years and 170k your rack bushings are probably shot anyway, so it is worthwhile to replace it and improve your steering and handling.

 

[Jstawgn]

The grease on the preload adjuster probably dry out and cause the adjuster to dig in into the rack. There is a spring and a mating cup behind the plug circled in red.

Do you have a prado with diesel engines or actual GX470? There is a video in YouTube for Prado diesel and they have a lot more room. It seems much easier to do on Diesel Prado.

 

[indridi]

I did my own rack as a DIY and it took around 8 hours. I also spent several hours messing with other things and getting a new power steering line. For an experienced mechanic with a lift, it would probably be a 4 hour job. You will also need an alignment after the rack is installed.

At 18 years and 170k your rack bushings are probably shot anyway, so it is worthwhile to replace it and improve your steering and handling.

Ok, nice to know that it's not more hazzle than that. My mech guy sounded like it would be more. He hasn't changed one in a 120, despite servicing a lot of those cars. So my worst-case scenario isn't quite so bad after all.

 

[indridi]

The grease on the preload adjuster probably dry out and cause the adjuster to dig in into the rack. There is a spring and a mating cup behind the plug circled in red.
View attachment 3095829

Very interesting. Would this match the fact that the stiffness is quite localized, and appears only when warm?
I'm not sure I get the mechanical details though. It's an adjuster with a lock nut I assume - when the grease dries out, does the adjuster come lose and sort of get turned inward by the shaking of the car?
Or is the dried-out grease inside the rack, behind the adjuster?
So, what needs to be done is to un-tighten the adjuster a little bit? Or remove it and fiddle with the spring and the mating cup (hope not, though, sounds very iffy with the rack still in the car?)

Do you have a prado with diesel engines or actual GX470? There is a video in YouTube for Prado diesel and they have a lot more room. It seems much easier to do on Diesel Prado.

It's a diesel Prado.

I can't seem to find the video you mention, @Jstawgn , do you mind posting a link, or the title so I can find it?

And thank you a lot for your answer.

 

[Rednexus]

Also, one other suggestion would be to install a power steering filter, like a Magnafine (see my build thread for pictures of how I installed mine). If you do put in a new rack, you don't want any leftover metal particles in the fluid damaging either your new rack or your old power steering pump. I'm not sure it's possible to get 100% of any debris/gunk out of the system even with flushes/fluid changes, so a filter is good insurance against future problems.

 

[Jstawgn]

Very interesting. Would this match the fact that the stiffness is quite localized, and appears only when warm?
I'm not sure I get the mechanical details though. It's an adjuster with a lock nut I assume - when the grease dries out, does the adjuster come lose and sort of get turned inward by the shaking of the car?
Or is the dried-out grease inside the rack, behind the adjuster?
So, what needs to be done is to un-tighten the adjuster a little bit? Or remove it and fiddle with the spring and the mating cup (hope not, though, sounds very iffy with the rack still in the car?)

It's a diesel Prado.

I can't seem to find the video you mention, @Jstawgn , do you mind posting a link, or the title so I can find it?

And thank you a lot for your answer.

This is the power steering rack replacement



This is the best flush method I use

 

[indridi]

@Jstawgn : in your original post, you said

[...] and cause the adjuster to dig in into the rack [...]

Would this mean that the rack is shot, and I need to replace it, or is there a chance that by re-adjusting the preload, I can keep using the old one?

And since I'm commenting : flushing the steering fluid in a prado diesel is actually even easier than in this video - I just pop off the return line and put it into a bottle that can lay around there in the plentyful unused space in there.

 

[Jstawgn]

@Jstawgn : in your original post, you said

Would this mean that the rack is shot, and I need to replace it, or is there a chance that by re-adjusting the preload, I can keep using the old one?

And since I'm commenting : flushing the steering fluid in a prado diesel is actually even easier than in this video - I just pop off the return line and put it into a bottle that can lay around there in the plentyful unused space in there.

Try removing that adjuster and see the condition. It need the preload from it to work properly. It it become too rough you need to smooth out the rack part and at that point a replacement would be much easier.