carfanmd

Happy holidays all. Quick question. I have a 2006 LX470, just shy of 88K on it. Fully serviced great driving car. I notice, however, that I have some creaking/rough riding noises coming from front passenger dash/door or center console when I drive over wavy roads such that the vibrations of the road travel into the cabin and make it sound harsh. Car is silent on smooth surfaces. I drive in Luxury/Soft mode so expected these to be minimal. Hydrolics have been recently serviced. Not sure about this but the travel of the ride seems a bit harsh. Any ideas? Any suggestions? Not a huge deal but I like the car to be very soft suspension wise. Thanks all.

kwatt1

The "hydraulics recently serviced" is suspect. Did a Lexus dealership serice it? If not, you need to find out what was put in the AHU. If you look at "AHU" threads you will find LOTS of cases where people put in the wrong fluid. Brake fluid seems to be the big one. If it was very recently done and AHU fluid was not used you need to jump on fixing it very quickly. Anything other the AHU fluid WILL cause the membranes in the dampener to fail. They are $400-500 each. Don;t let anyone try to tell you it doesn't matter what fluid you put in there.

If you aren't sure, open the AHU resevoir (big white resevoir on the PASSENGER side by the firewall.) and look inside. New AHU fluid is PINK. IF the AHU was recently serciced the fluid should still be pink. If its brown or anything other than pink or you are suspect to the fluid used. Get 3 cans of AHU fluid (from LEXUS) and FLUSH it asap. Each bottle of AHU fluid will do 1 flush so you'll be doing this 3 times. AHU is about $40 a can. This is a very easy system to change fluids. It will take less than 30 minutes to do the whole thing.

- Set the ride height to LOW and let the vehicle drop down
- Get a hand vacuum pump and suck all the fluid out of the resevoir.
- Fill the resevoir about 1/2 way. It will hold tbhe entire can but you don't want to contaminate the new fluid with the residual stuff in the resevoir.
- Locate the bleeder for the accumulator. It's behind the front wheel and higher than the wheel dampener. If I recall correctly, it's on the passenger side, but I cantt swear to that.. Connect a tube to the bleeder. You want to createe a loop/hump so the fluid is forced up before it goes down. This will prevent air from entering the system and you can also see if you had air in the system if bubble comes out.
- Very slowly open the bleeder. The vehcile will collapse down so watch your head and let it go slowly. If you made the hump/loop it won't matter if you let it bottom out. If not, pay close attention to how far it moves so you don't bottom it out and let air in..
- Close the bleeder and start the vehicle to let it pump up. Set the comtrol to High which will pump the vehicle up as high as it will go. DO NOT allow the resevoir to run empty All that will do is pump air into the system and then you will have to do all this over again to clear the air out.
- Refill the resevoir to about half.

Follow the same procedure for each wheel (don't suck out the AHU fluid from the resevoir after the 1st time). The bleeders are all next to the dampeners. The rear's are in front of each rear wheel and the front's are behind each front wheel.

After the accumulator, Start with the rear wheels since that is the furthest point from the resevoir. Keep filling the resevoir so it never runs empty. Each time you purge the wheel, that pushes the bad fluid out of the hydraulic cylinder (shock absorber) and pulls the clean fluid through the tubing when it refills. This should be done every 60K miles as per your drivers manual.