sweeks

I've recently acquired a 2005 RX with air suspension.

It drives well but there are two things that bothers me.

1. I hear a knock at low speeds coming from the rear.
2. When taking corners at medium to high speeds , the vehicle seems a bit unstable.

The entire front suspension was changed out a year ago. And all the rear bushings and arms seems fine.

Are the rear shocks shot?

RX330inFL

Air suspensions are usually either good or bad. There is really no in between. If there are no lights on the dash to indicate a problem and if all the bags inflate and they function as they should that is about as good as it gets.

The knock is very subjective and could be many things. Did you check the hatch area to make sure all the tools and such are in place and not moving around? Have you tried different settings on the air suspension to see if the noise goes away at these lower speeds?

As for being unstable while taking corners at high speeds, this RX is a tall wagon and not a sports car. The air suspension is as much about ride comfort than anything and really does not make it any more sporty. Does it adjust properly to the three settings of high, normal and low? Have you tried turning the air suspension off to see how that changes the ride characteristics for you?

http://drivers.lexus.com/t3Portal/do...6U/pdf/3-1.pdf

Not trying to be dismissive, however, you do not give us much to work with in trying to diagnose your problems. Can we assume by replacing the front suspension you mean they replaced the power steering rack? Or, did they change out the front pneumatic struts?

sweeks

I'm fairly new to air suspension.

No lights are on in the dash. Are you saying that if there's a problem with the struts, a warning light will come on? I will road test using the different modes over the weekend to see if the noise goes away while in any particular mode. However I don't believe there is an off button to turn off the air suspension (will have to double check).

BTW I did notice some uneven wear on the rear left side tyres.

The struts, stabilizer bushings, link assemblies, ball joints and lower cradle arms were replaced. The power steering rack was not replaced.

Thanks for responding.

RX330inFL

The URL I provided shows the appropriate section of the Owner's Manual discussing the air suspension you will need. If you do not have those buttons you do not have air suspension.

HtownBlue

If you have a bad air strut, one side of the vehicle would likely look lowered at times as opposed to normal. Lights on the dash usually indicate failures not worn out issues like a worn inner strut or a leaky air bag.

RX330inFL

OK, uneven tire wear is something to work with. Is the tire cupping or is it just wearing unevenly across the tire with the inner or outer wearing more?

As HtownBlue mentioned, one side may be lower than the other as an indication of a problem. Get out the tape measure and try setting the vehicle at each of the three height settings: hi, normal and low. Check the body height to see how each side compares in the rear. Do you have family? If so, open the hatch and have them sit in the hatch area to see if the extra weight causes one side to be abnormally low. Also, try the bounce test in that one corner with the abnormal tire wear -- somewhat old school test. Any noises? Does the vehicle continue to bounce? Should be one bounce and stop. Here is some additional information to help explain what to test for or ask about. Even though you have the air suspension the thought process follows:


Wow, that was a lot to have replaced.

sweeks

Our RX is currently doing 65k miles. And it has air suspension. There isn't a button to turn off the air suspension but there is the Height Control switch on the center console and an indicator (Lo-N-Hi) below the tacometer on the instrument panel.

I did the road test last night using the different settings. In all modes I got the knock coming from the rear. (I even got a knock from the from going over a speed bump in the Hi mode but I'm not too worried about that)

The tire wear is taking place on the outside of the left rear tyre (Michelins 255/55 18s).

On a flat surface, the vehicle looks level from the front and from the rear. However I will confirm later with the bounce test and measuring the three heights.

RX330inFL

The On/Off switch is there. You have to look for it under the dash. Check your Owner's Manual and/or the the section of the same I provided in the above URL on page 437. You will need to familiarize yourself with that section of the manual to understand how the system works.

HtownBlue

Mine went out twice. Once on front, and one rear. Neither time had a clunk from rear either time. If it was out or bad, you'd feel the entire car bounce up and down and it would be leaning to one side. If not, unlikely that it is bad. Your height should be about 33 inches I think from ground to fender. Maybe 31? Can't remember. Regardless. Stand behind your ride. Look to see if it is leaning to one side or the other. Report back or don't ask for further advice.

Not trying to be a *****, but both of us have told you things to look for and you have failed to do so or at least failed to post that you did. We can only help you so much if you do not perform the tests we ask.

sweeks

Front 33 inches
Rear 32.5 inches

The ride feels firm and it doesn't lean to any side.

There is no on-off switch. My particular model came out of Japan, and I'm located in Trinidad WI. I've been through this section of the owner's manual and have a fair idea of how the system works.

My wife uses the RX most of the times, hence the delays in responding. I'll continue troubleshooting the knock as time goes by.

sweeks

I recently took everything out of the car and test drove it. Apparently the tools in the booth area weren't secured and was knocking every time the car went over bumps.

Thanks for the help guys.

RX330inFL

Some times it is the simple things. Why I had asked if you checked for this exact problem.

sweeks

Yup ... The thing is that I don't have that much time with the car. Thanks again.