jonasolof

The LS400 that I have owned since I bought the car in 1991 now has 240k kilometers (150k miles). There is an intermittent problem with height adjustment. Sometimes the left rear sinks down regardless of high/normal button position. Sometimes it sinks symmetrically. And sometimes the car is raised as it should be when the button is in high position. I have a feeling that having suspension in sport helps somewhat.

It seems that the front is always high. If the rear is also hight, the car will remain high when parked - also for several days. I have photos of the car in high position front and rear and in high front low rear. The button in the trunk is "on".

The behaviour is erratic and I have not figured out what determines the behaviour. I have also noticed that air pressure is no longer released a while after the car is locked.

I need some clues when going to the nearest Lexus rep. since their experience with the older LS400 is very limited here in Sweden.

I have ordered second hand pneumatic suspension left which I found in Sweden, this since the problem started with the left rear not lifting. However, it seems that the problem is more more complex since the car can go high front and rear symmetrically sometimes. Could be a height sensor problem if there is one for each wheel. If the car is low in the rear, the ride is very bumpy from the back. When high it is OK, also when driving so fast that the car swiches to norm.

In high position and rear high. Car is level longitudinally and sideways. Sometimes this works but I can't find a way to force it.

Button is on high but rear is low. Front is always high, also when button is on normal.


Regards

Jonas

sha4000

iTrader: (1)

Your air suspension might be on its way out. Do you hear the air compressor running all the time? If so there could be a leak in the system. I doubt that they are still making parts for the factory air suspension in your car so you might have to start looking into converting it to regular shocks.

jonasolof

No sound from any compressor. As noted, when the system works and the car is put in high position, the car can remain high for several days. The front is always high.

sometimes the rear is lifted and then symmetrically. In the beginning, it would be low in the rear left. Now it is low on both sides, except the occasional time that the system decides to go high.

There could be a faulty cylinder although there can't be a constant leak. I believe there is a fault in sensors.

Yamae

I'd check the sensor's voltage first. It should be about 2.5V at the middle and almost 0V @ lowest and almost 5V @ highest. Also does the sensor send the voltage to the controller without any glitch/dip/pip? It would be the best to check those using an oscilloscope. But an analog voltage meter could be used if an oscilloscope was not available. A DVM can be used but it's not very easy to check the those strange voltage swings.

deanshark

My experience with the air on my 93; The left rear started going first, then the right rear a month after not repairing the LR. It eventually turned out to be slow leaks in the shock cylinders. The air would drain over night. If I started the car and put on "high" it would raise back up in about 5 minutes. Starting and leaving in "norm" did nothing, unless I drove it for a few miles then it would lift up. I converted the rear with conversion shocks. Then the front started acting up so I converted those also. I just decided to convert to regular cuz parts were too expensive at the time and once one thing goes, then other parts are going to follow. Gotta think, those parts are 30 years old. Hope your used shocks work out for ya cuz chasing down parts can get expensive and aggravating. Height sensors, compressor, actuator, ECU.

jonasolof

Thanks. I appreciate learning from those that chose to change shock absorbers because of slow leakage in the pneumatic cylinders.

in my case, the car has recently emained level and hight for 36 hours after ignition was switched of and height button in high position. Thats when I took the first photo. The distance from the ground to the top of the wheel well was 72 cm all around four wheels so there can't be a leakage since I doubt that the height adjustment compressor would work when the key is out of the car.

deanshark

I haven't dealt with the air for about 8 years now but if I remember correctly, (when it was working right) mine would drop about 2 inches out of all the shocks very slowly when the key was turned off and then raise back up again when the car was started. I used to love the air ride but it got very aggravating when it started to go bad.

jonasolof

Thanks for your input. I have noticed already some time if and when the car was in high position as the key was turned off, the car would not sink at all. There seems to be some logic which has become scewed up. One could believe that this is because the car is already low but that is not the case as can be seen from the first photo.