additude

I bought this bad boy in 2000. I only have like 125k miles on it, but it's showing its age. Recently had to replace the steering power cylinder and lines. All was good for about 6 months and then started noticing that the drivers front wheel air suspension was deflating after the vehicle was turned off. That went on for a few weeks before I had time to investigate it. The wife said the other day that it was like spooky driving it from work to home, maybe about a mile and a half home. She had a few days off and I looked at the car. It was deflated, as usual on the driver front and I started the car up and waited, but the drivers front didn't rise back up. So, I toggled the Height Hi/Lo switch back and forth a few times and it started to rise. However, all 4 wheels on the car rose in height all the way to maximum. Even higher than the normal "Hi". I shut the car off and I let it sit for a while, but none of the air shocks deflated at all including the drivers front, did not deflate. I disconnected the positive battery cable with car shut off; car still held its height. Connected the battery and started the car, and the height settled back to normal, except the passenger rear now stayed at the "over hi" level. I messed with starting, stopping, using the height switch between Hi/Normal for a while, turning the Height switch to Hi, then to Low (Normal) several times, but I couldn't get the car to raise or lower again between Hi and Normal. So, now I'm back to it acting just how it was before, deflating the driver front after the car is shut off and now the passenger rear stays over inflated.
Any ideas?
Thanks.

timmy0tool

iTrader: (7)

the car has low miles but the air suspension components don't age as well as the rest of the car. sounds like the air valves are sticking open or closed, and/or you have a leak in the system (usually at the air bellows around the shocks but can also be at the lines).

arm yourself with soapy water and spray it on the air suspension lines and bellows. any leaks will present themselves with bubbles!

most folks here convert their car to standard strut/spring combo to not have to deal with these air suspension woes.

additude

Hi and thanks for the reply. It seems to me that if the air shocks would over-fill and then stay over-filled for a while after I shut the car off, then there shouldn't be any air leaks. At first, I thought some air leak related to the driver front, because it was deflating, but the driver front stayed over-filled as well and it didn't deflate until after I restarted the car. Then driver front went back to normal...and now, deflates as had been doing.
Things seem inconstant.
Thanks.

paulo57509

Does the '97 set trouble codes for the pneumatic suspension (blinking Height/Hi indicator on the dash)?

CELSI0R

This might be worth a watch.

Even though it's for the first gen model, I would assume it should be similar to the 2nd gen LS:


At 3:40 it's mentioned that there is a level sensor at each wheel of the car. If this is the same for the 2nd gen model and you are finding that the system does correctly hold air, this sensor may need to be checked.

I would still double check for leaks with soapy water as per Timmy's suggestion

timmy0tool

iTrader: (7)

good idea on the height sensors. i forgot about those which can get bent or even break off.

additude

Unfortunately, the blinking Height/Hi light is not blinking and I have verified it is operational.
Thanks.

additude

I will check this link out as well as the use soapy water.
Thanks.

Yamae

Sounds like the air suspension computer is not functioning well enough to me. Without analyzing it myself, I can't say enough, but as an EE, I'd check the voltage regulator and the ON/OFF reset circuit using an oscilloscope. Your type of problem is sometimes caused by the poor regulation of the voltage regulator and the unstable voltage causes the malfunction of the reset circuit as well as the processor's abnormal run which doesn't show any error code like the engine ECU acts when the ripple voltage is too much.

deanshark

I had a 93 which acted the same way. It would leak out the passenger rear at night and then blow back up when I started the car. And same as yours, if I put it on "high" it would go extremely high. After a while of driving like that, maybe 10 miles, the back would go lower then usual and front would stay high. It looked like a "lead sled" from the past. I was able to hear the air leaking from the rear shock.
I ended up putting on conversion shocks, just on the rear and kept the front air, (financial reasons) for about 2 months then a front shock started leaking so I did the same. Better to do all 4 at same time. But if you do change over make sure you get some good ones. Don't go cheap like I did, it wasn't worth it. Plus, once you start having problems with the air, you'll always have more problems. Another part will break after the first is fixed.

CELSI0R

Part 2 of the air suspension video, just in case it's helpful for thinking of the diagnostic approach:


This one talks about the wheel sensors and how the car determines the vehicle height from them.

additude

I was able to order the replacement caps for the ECU. I haven't changed them out yet.
I have watched both video's, which were very helpful. I performed the tests in the first video. All tests worked. I need to do the tests in the second video. The videos are for a pre-1996 LS400. Mine is a 1997, so there are some differences. In the 1997, I think the ECU is up by the glove compartment, the videos show it in the trunk. I spent most of my time just gaining that knowledge.
So, I need to breakout the connector on that ECU and perform the tests.
So far, with just normal operational testing, I have had inconsistent results. I've had the vehicle stay inflated for over 2 days, then it would just deflate. Opening the driver's door before turning off the ignition and having the height switch to "Hi", will keep the vehicle inflated, most of the time. But not always...

mikaelse

My 1998 also has air suspension. It is giving me no problems at all. Never deflates and also shock action is OK after 24 years. However I can not claim that is is in anyway better than my 1995 winter car with normal spring suspension. (However There I had springs breaking due to corrosion that needed replacing in the rear.)
Your problem sounds like is logical at least partly.
Leaky airspring belows in the shocks is normally what happens with age/mileage. Leaky valve on driver front wheel is also reasoanbly a possibility but sounds less likely to me.
If you aim to keep the air suspension that leakage should be fixed promptly since the pump is working overtime.
I guess is that your driver side front airschock needs to be replaced. Some people has the idea to replace ONE airshock with a used one but if more stuff breaks they convert to normal springs on all four. You can sell working air shocks and pump.
There are also height sensors on all corners. These can also malfunction. More common it seems though in the LS430.
The multiple strange things that happened to you more indicates a control issue . I do not know which controll box handles this stuff or what to do about it.

C0nn0r91

The height indicator in the dash cluster can be used to give you trouble codes if needed.

See attached photos from the lexus maintenance manual.