Ls 430 Sunken Rear Suspension

Jackie Brambles · January 8, 2013

Hi All, I have a 2001 LS 430 with air suspension. The suspension on the car never gave any problems whatsoever until I parked the car up for 12 months. When I restarted the car after this time the rear of the car was sunken to the ground and did not pump itself up as normal. I have been unsuccessful in trying to get anything to work. The fuses are fine, the relay is fine, the height sensors seem fine. Any help would be gratefully received. Thanks in advance.

ambermarine · January 9, 2013

Hi

Welcome to the club,

The issue here is the time the car as been stood idle, problem with air suspension is it needs to be constantly working as the seals are only going to work properly in the operative mode as they are designed that way.If the car as been unused for a long period the seals dry out and the bladders distort and perish in the same way a tyre does that as not been used.I assume the car is driveable so I would ask Lexus to give you an opinion as the air systems are usually peculiar to individual manufacturers and they will have the background knowledge that should identify the problem.Alternativly you could download a workshop manual from the web (About £10) and troubleshoot the cause, the issue here is specialised equipment ,the need of .

Best of luck.

steve2006 · January 10, 2013

Hello and welcome to the LOC.

As Ambermarine has said these systems need to be used regularly or things fail similar to an unused AC system where seals perish with lack of use.

Have you tried running the engine for an extended period of time to see if the suspension rises?

It is unusual for both rear airbags to fail at the same time, the Air Suspension pump is located in the front O/S wheel arch along with the front height control valve, if the front is at normally height it could be assumed that the pump is working.

There is another height control valve in the n/s rear wheel arch which controls the rear suspension.

The system is complicated and as suggested it may be a good idea to get the car transported to a dealer for at least a diagnostic check. From there you could either have the repairs carried out or once you know which parts have failed buy some good secondhand ones and have them fitted at an independent garage.

I would not recommend driving the car with the problem as it could cause further damage, if you have breakdown cover get them to transport the car.

I don't know how savvy you are with car electrics but there is a method in the factory manual where you can run the compressor continuously for a short period to see if the suspension then responds.

You can also look for leaks in the pipework and unions by spraying a soap solution on them and looking for bubbles.

One final suggestion is to remove the link rod on the rear height sensor and manually adjust the sensor arm from its highest to lowest position to see if this activates the airbags, there have been cases where these devices have contaminated electrical tracks internally and then fail to give an output signal to the ECU.

ambermarine · January 11, 2013

Hello and welcome to the LOC.

As Ambermarine has said these systems need to be used regularly or things fail similar to an unused AC system where seals perish with lack of use.

Have you tried running the engine for an extended period of time to see if the suspension rises?

It is unusual for both rear airbags to fail at the same time, the Air Suspension pump is located in the front O/S wheel arch along with the front height control valve, if the front is at normally height it could be assumed that the pump is working.

There is another height control valve in the n/s rear wheel arch which controls the rear suspension.

The system is complicated and as suggested it may be a good idea to get the car transported to a dealer for at least a diagnostic check. From there you could either have the repairs carried out or once you know which parts have failed buy some good secondhand ones and have them fitted at an independent garage.

I would not recommend driving the car with the problem as it could cause further damage, if you have breakdown cover get them to transport the car.

I don't know how savvy you are with car electrics but there is a method in the factory manual where you can run the compressor continuously for a short period to see if the suspension then responds.

You can also look for leaks in the pipework and unions by spraying a soap solution on them and looking for bubbles.

One final suggestion is to remove the link rod on the rear height sensor and manually adjust the sensor arm from its highest to lowest position to see if this activates the airbags, there have been cases where these devices have contaminated electrical tracks internally and then fail to give an output signal to the ECU.

You could'nt get better advice anywhere, nice one steve you hav'nt pm'd me yet.

ipwn · January 12, 2013

You could come to my house if you ever near my neck of the woods, I have Techstream if you want it connecting.

Jackie Brambles · January 18, 2013

Hi all and thank you all for your advice and your kind offer IPWN. I have had a chance to spend the afternoon working on the car and have the following update. When the car is jacked up fully (each of 4 wheels) the front wheel hang down a long way from the car (as per normal) but the back wheels stay right up next to the wheel arches. The fuses and relays to the air suspension were tested and are definitely ok. I believe I found the air compressor for the suspension. If I am correct it is on front of the right front wheel just behind the bumper. It does not appear to be working at all. Why then are the front wheel not sunken as per the rear. If I remove the compressor could I test / verify that it is broken. What I do not want to do is to buy a new compressor and find that it is an ECU problem or similar.

mikesands · May 13, 2013

Jackie.

I now have the exact same problem as you - did you get it sorted?

Thanks

Mike

Dom175 · October 23, 2013

Hello All,

I have a 2002 LS430 and I think the suspension is inoperative presently. Car looks high at front and low at rear. It is presently in sport with low ride height, should this be the case as I know it is not a sports car but luxury car. I don't hear a pump when I change the ride height, is this something you would normally hear? Are there any obvious checks I can carry out at home easily with limited tools?

Thanks and love the forum, it's always great knowledge. Dom

steve2006 · October 24, 2013

Not sure if the LS430 is the same but I have an LS400 on air suspension and I can definitely hear the pump when high is selected and the hissing of escaping air when reset to normal.

Apparently the height sensor units are prone to failure on the 430 which may be the case,they can be tested and checked with the correct diagnostic equipment, this will obviously cost you at Lexus but at least you will then know where the problem lies.

mikethebike · November 12, 2013

The rear sensor has snapped off on mine, probably because its seized (the suspension seems to be in correct position thankfully).

Lexus dealer has quoted "somewhere in the region of £300 for the sensor"...gulp!

Maybe I should start looking for one being broken up and get the sensor...seems easy enough to fit?

Weloveourcar · August 13, 2016

Hi, I'm a newbie, I have a problem with my near side rear suspension on an RX300 2003 model. We took the car to Lexus and they diagnosed the nsr height control sensor needed replacing, as they could t get a part u til next Tuesday, and the fact that we are on holiday Monday, I asked what could we do to get the part, they told me that they sell the genuine part on eBay and with next day delivery it could be done before Monday. The part arrived and I took it in. The next day, all fixed and collected the car, 13 mile trip home all back to normal. Our next trip out it reverted back to the original state, rang Lexus today's and they are trying to say it's the part, logically, it's highly unlikely? A brand new genuine part? Surely it's something else happening, we have to take it back on Monday, putting our holiday back and buying another part is another £218.... Help please?

steve2006 · August 14, 2016

Lexus recommended eBay for the part?

If parts are in the UK then Lexus can usually get them delivered next day especially with a commonly failing part as the height sensor, was the eBay seller a Lexus dealer as I know certain ones do list parts and did it come in genuine Lexus packaging as certain far eastern countries are very good at couterfeit parts.

Looks like a case of having the part fitted again and then sending the eBay one back to the seller for a refund.

Sorry I know this isn't much help or comfort but if Lexus do supply the part and fit it there will be a warranty on it.

Finally welcome to the LOC, please keep us posted on what happens.

DaKa · September 27, 2017

I hope that you get the original air suspension working soon.

I would imagine that other than donor parts (that can't be trusted) and of course the knowhow/equipment to fix it yourself, this could be expensive.

I'm just wondering if an after-market adjustable rear suspension kit would be both better and cheaper?

I recall an episode of Wheeler Dealers where they did the same for a Mercedes I believe?

MLW · September 27, 2017

Yours sounds pretty bad.

However, I did an oil change, and started the car up in the air to check for leaks. All OK. Lowered the car and the suspension had dropped right down. Total panic as it was OK before, totally normal.

Decided to drive it. At this stage it came up. After about a mile, totally normal. If you can drive it, maybe try doing so and see what happens. Mine 'sorted itself out' a year ago and has been perfect since.

The driving cured it. Maybe when it moves, the computer says time to 'pump up'.

ScottishLS · February 20, 2021

Late to this thread but bought my first LS430 bronze 2001 yesterday.

The owner an older gentleman for the last 6 years.

Said the rear suspension became temperamental after going through a big puddle and has now completely stopped raising. I tried jacking it up on the day before collecting it and both wheels came up. Drove it home and it was bouncy as ****!

Today I jacked it up as I couldn't hear any hissing from the air bags, nor did it scrape on the ground the entire journey. As I jacked it up both sides the wheels stayed down, so I believe I've freed the struts as the car was sitting for a long time like that but it fell back down after taking the jacks out.

Before I get right under to check the components and the solenoid for water in them or incase they are loose.

Would a blown fuse next to the relay in the fuse box under the bonnet cause it drop?

The relay and the fuse in the drivers side door panel are fine.

There is no noise at all for it to even attempt to raise even pressing High height on the centre console.

Any advice is appreciated as I've had help from a breaker assisting me but want to know a little bit more from anyone with a similar issue before I get struts incase its a cheaper job than I imagined cheers!

George

The-Acre · February 20, 2021

There is a 40 amp fuse for the suspension system under the bonnet near the Battery, have you checked that? Mine is a Celsior so some positions of components can be slightly different but I'm happy to take a picture of the fuse compartment in the morning if it helps. If you can't hear the pump running at all it could well be the fuse or the pump has gone kaput from over work. The height sensors are prone to water ingress so the story of the puddle could be right. You can dismantle the sensors to clean and reseal if they haven't been too damaged. Removal of the sensors is easy enough, and no need to be concerned about the removal and replacement of air struts, it's very straightforward, but parts are very expensive!

Brik · April 5, 2021

On 1/10/2013 at 10:15 PM, steve2006 said:

There is another height control valve in the n/s rear wheel arch which controls the rear suspension.

I've tried to find this valve on my early '02 LS 430 and there is nothing in the n/s r wheel arch area, following the pipe work back from the strut there is a valve under the car towards the centre.

steve2006 · April 5, 2021

The control arm is shown highlighted Richard, according to the diagram there is one on each corner, find the arm and the sensor is connected to the top of it.

Brik · April 5, 2021

Thank you for that, I found the height sensors but they just measure each corner of the car and send an electrical signal to the controller, there are no air lines on them so they are not a valve.

https://drive.google.com/file/d/1UxovRSfZnNsN9LFi-Sx68AvdoztEnb9X/view?usp=drivesdk

BigBoomer · April 6, 2021

The output from the suspension compressor must have a multiplex valve system that pressurises each shock according to the info it receives from the level sensors. I very much doubt that they will be individual valves unless they are in the strut itself, which is a possibility. How many wires connect to each strut, in addition to the compressed air line? There will be one pair of wires for the shock damping control and another for the valve, if it's in the shock.

The-Acre · April 6, 2021

2 hours ago, BigBoomer said:

The output from the suspension compressor must have a multiplex valve system that pressurises each shock according to the info it receives from the level sensors. I very much doubt that they will be individual valves unless they are in the strut itself, which is a possibility. How many wires connect to each strut, in addition to the compressed air line? There will be one pair of wires for the shock damping control and another for the valve, if it's in the shock.

The shock must have valving inside as there's a sensor/controller that plugs into the top of each unit.

Brik · April 8, 2021

On 4/6/2021 at 3:55 PM, BigBoomer said:

The output from the suspension compressor must have a multiplex valve system that pressurises each shock according to the info it receives from the level sensors. I very much doubt that they will be individual valves unless they are in the strut itself, which is a possibility.

As I mentioned above, there is a unit under the rear of the car, near the diff.

This has two valves on it that, I guess, control the amount of air going to the struts.

https://www.ebay.co.uk/itm/New-Lexus-LS430-Air-Suspension-Rear-Valve-Block-Height-Control-No-2-4809650040/203335283824?epid=1713774933&hash=item2f57ba3470:g:0yMAAOSwXXpgaL3O

Edit:- Just found the unit online.

BigBoomer · April 9, 2021

That's the beastie. :thumbup:
The wires going to each shock are for the electronic damping adjustment Phil. 🙂

The-Acre · April 9, 2021

12 hours ago, BigBoomer said:

That's the beastie.
The wires going to each shock are for the electronic damping adjustment Phil. 🙂

The shock still has valves inside. There has to be valves inside to allow air to escape/ be replenished.

Brik · April 10, 2021

On 4/9/2021 at 8:47 AM, BigBoomer said:

That's the beastie.
. 🙂

Yep, and today after closer inspection I have found this part to be leaking from the plastic housing, caused by it's metal bracket corroding.

21 hours ago, The-Acre said:

The shock still has valves inside. There has to be valves inside to allow air to escape/ be replenished.

The shock is a sealed unit filled with oil, there maybe some electrical magic added to adjust the firmness.

The 'spring' is the airbag which is controlled by the valves I linked to above, they are mounted externally and adjust the amount of pressure in each bag accordingly.