RX 300 2004 UK suspension issue

Roger001 · July 4, 2022

Hi there

i have a 2004 RX 300. UK

Rear suspension won’t work.Air bag has been replaced. Compressor has been replaced. Valve has been replaced. All by a Lexus dealer. Still has the issue.

Any Suggestions ?

Herbie · July 4, 2022

Quite a few people take this as an opportunity to get rid of the air and change to standard coils. A whole set of four coils/struts can be had for not much more than the cost of just one air strut and you'll never have the problem again.

b4u2 · July 4, 2022

What did the dealer suggest @Roger001

Roger001 · July 4, 2022

He didn’t know. No air leak found. Then compressor changed. Then valve unit. Still the same. I took it to them as they should be the experts ?

Roger001 · July 4, 2022

The dealer thinks that the air isn’t getting to the air suspension unit.

Neil E · July 4, 2022

1 hour ago, Roger001 said:

Hi there

i have a 2004 RX 300. UK

Rear suspension won’t work.Air bag has been replaced. Compressor has been replaced. Valve has been replaced. All by a Lexus dealer. Still has the issue.

Any Suggestions ?

That sounds very expensive not to have resolved the fault. A Lexus technician should know if the compressor pump is working or not and whether the air is reaching a suspension leg or not and be able to detect if there is a leak. Has the Lexus dealer charged for all of the parts and labour so far?

Is it one rear corner or both? If it's one side, did they check the height controller first?

Roger001 · July 4, 2022

They haven’t charged me for parts. The air bag was replaced under warranty (I had only just bought it in Nov last year) by the garage I bought it from and replaced and calibrated by one Lexus dealer. It was repaired three months later.

the suspension then went two weeks later and has been with another Lexus dealer. They allowed me to supply third party compressor and valves as they couldn’t get the parts ? They have just agreed to waive labour charges so far.

Car drives like a kangaroo jumping. Both sides.

Neil E · July 7, 2022

It sounds like they don't know what they are doing and the car isn't fit to drive.

Do you have pictures of the parts supplied? Pics or a video of the car might help too.

Is the suspension completely down on both sides at the back or is it uneven in height? On a flat surface measure the arch lip to the tyre on both sides to see if there is any height difference.

Does the steering pull to the left or right?

If the car is started and left to idle, switch to the 'high' setting, does the air pump 'run' and does the rear raise up at the back at all on either side?

Most air sus faults are caused by faulty height controllers but if a leg is losing air through a leak then it usually has to be replaced. Sometimes you can trace the air leak by ear and touch.

Malc · July 7, 2022

On 7/4/2022 at 7:57 PM, Herbie said:

get rid of the air and change to standard coils. A whole set of four coils/struts can be had for not much more than the cost of just one air strut and you'll never have the problem again.

Oh my Neil ... if your car is free of rust and all else is good to go then for heaven's sake bite the bullet, save yourself a fortune, and do the above

Malc

Roger001 · July 7, 2022

I considered doing that but you have to notify the insurance company ?

air bags on suspension are a disaster waiting to happen.

Could the height sensors being corroded be the issue ?

Thanks.

Neil E · July 7, 2022

If the height sensors (height controllers) are faulty or stuck, yes that could be the cause but a trained technician can establish what's wrong by checking everything carefully.

13 hours ago, Malc said:

Oh my Neil ... if your car is free of rust and all else is good to go then for heaven's sake bite the bullet, save yourself a fortune, and do the above

Malc

Hi Malc, quite the opposite, I've had 3 cars with air suspension and saved a fortune by fixing them instead of following poor advice to replace all of the suspension legs with lesser standard suspension. I don't deny that eventually they can fail like normal struts will wear and 4 brand new air struts would be a fortune for a complete refresh but if you take the trouble to learn about the air system, they really aren't as scary as many make out.

I've explained before that owners will write off a whole car because someone can't find an air leak or diagnose a fault with a little height controller that takes 20 minutes or less to replace. The term air 'bag' makes them sound flimsy but they're actually quite robust and reliable.

PCM · July 8, 2022

... in the last 4 years or so, all my air struts have been replaced ( 3 under warranty ).

Never sure if I can sense the difference or not, but i do like the height adjustment button!

Rust on the frame has been a bigger issue for me...

Roger001 · July 9, 2022

I supply workshop diagnostics to workshops throughout the UK and teach and train technicians.

if the height sensors were the cause of this issue and could cause this fault then this would be a massive error for a workshop to make.

when the problem occurred it was 2 weeks after an air strut had been replace and the sensors calibrated by another Lexus dealer.

it was very heavy rain and driving through a puddle there was a squeal and then the car started to bounce.

The conclusion from two garages, one a Lexus dealer is that the air isn’t getting to the rear suspension units.

no leak can be found. Rear solenoid valve sets have been replaced, compressor has been replaced

both height sensors going at the same time would be very unusual.

Herbie · July 9, 2022

53 minutes ago, Roger001 said:

The conclusion from two garages, one a Lexus dealer is that the air isn’t getting to the rear suspension units [...] no leak can be found.

The laws of physics can't be defeated - it's only air from a source, travelling through a pipe to a destination.

If the air is being pumped out by the source and going into the pipe, but crucially not reaching its destination, it can only be either escaping before it gets there, or its being blocked from getting there.

First, get a jam jar and put some water in with a few drops of washing up liquid and then, using a brush, brush all along every pipe and every joint. Leaks will form bubbles.

If there are no leaks, take each section of pipe off in turn and either try to squirt water through it or blow compressed air down it. That will show up any blockages.

Roger001 · July 9, 2022

First thing both workshops did was look for a leak. I don’t know if they have tried a blow though. I’m sure it’s the second thing Lexus should have done. I’ll double check. I know it’s a very simple system. 3 months !!!!!

Neil E · July 9, 2022

On 7/7/2022 at 1:16 AM, Neil E said:

Do you have pictures of the parts supplied? Pics or a video of the car might help too.

Is the suspension completely down on both sides at the back or is it uneven in height? On a flat surface measure the arch lip to the tyre on both sides to see if there is any height difference.

Does the steering pull to the left or right?

If the car is started and left to idle, switch to the 'high' setting, does the air pump 'run' and does the rear raise up at the back at all on either side?

I asked the questions above to determine whether the air compressor is actually working, is there any air in either side of the rear of the car and are the height controllers calling for air to each corner or not?

PCM · July 9, 2022

3 hours ago, Neil E said:

I asked the questions above to determine whether the air compressor is actually working, is there any air in either side of the rear of the car and are the height controllers calling for air to each corner or not?

Does it make a noise?

I know I hear mine when it's 'doing' some work... ( not all the time, maybe when I have stopped on an incline ).

Roger001 · July 9, 2022

Both the old compressor and new compressor are working. They thought the old one wasn’t giving out enough air pressure.

Herbie · July 9, 2022

On 7/7/2022 at 1:16 AM, Neil E said:

Do you have pictures of the parts supplied? Pics or a video of the car might help too.

Is the suspension completely down on both sides at the back or is it uneven in height? On a flat surface measure the arch lip to the tyre on both sides to see if there is any height difference.

Does the steering pull to the left or right?

If the car is started and left to idle, switch to the 'high' setting, does the air pump 'run' and does the rear raise up at the back at all on either side?

Most air sus faults are caused by faulty height controllers but if a leg is losing air through a leak then it usually has to be replaced. Sometimes you can trace the air leak by ear and touch.

5 hours ago, Neil E said:

I asked the questions above to determine whether the air compressor is actually working, is there any air in either side of the rear of the car and are the height controllers calling for air to each corner or not?

Just to add to that - it is possible that the compressor is actually working but is 'weak' and can't pressurise the pipework. I have no idea what pressure these things are meant to run at.

Herbie · July 9, 2022

Haha, just seen that the OP replied while I was typing that out. Ignore that then :laughing:

Herbie · July 9, 2022

7 hours ago, Roger001 said:

First thing both workshops did was look for a leak. I don’t know if they have tried a blow though. I’m sure it’s the second thing Lexus should have done. I’ll double check. I know it’s a very simple system. 3 months !!!!!

Indeed it is, and it will be an equally very simple fix - you've just got to find where the fault is.

Assuming that it is just an air problem and that the mechs/techs who've looked at it so far have ruled out, beyond any doubt, any electronic and/or sensor problem, it can only be one (or more) of four things:

The source of the air, ie, the compressor - which you've ruled out
Pressure not high enough from the compressor - which you've ruled out
A leak or a blockage on the way from the compressor to the struts
Air is reaching the struts at the correct pressure but the struts are faulty and can't use the air to do their job

I used to be a telephone engineer on BT and all of our old copper trunk and junction cables (and also the modern fibre optic cables) that go from exchange to exchange, or from exchange to the green street cabinets, are all pressurised to 9psi. The reason for this is twofold - if there's a fault then air coming out prevents water from getting in; and secondly, once the cables are pressurised there should be no flow. If air starts to flow (in what should be a sealed system) then pressure alarms ring and we can measure the approximate location of the fault.

I know that chasing an air leak on the Lancaster - Manchester No.6, or the Preston - Blackpool No.2 is different to chasing a problem around a car, but the basic principles apply.

Neil E · July 9, 2022

1 hour ago, Roger001 said:

Both the old compressor and new compressor are working. They thought the old one wasn’t giving out enough air pressure.

That's good....so if the compressor is working and the rear suspension is down, the left and right rear height controllers should confirm the low level and signal for air. The compressor pump should be whirring to supply the air until the rear reaches the correct height and then it will cut off. (which it isn't doing as the rear of the car remains low)

If the compressor keeps pumping and the rear doesn't go 'up,' that would suggest an air leak. (no leak found)

If the compressor doesn't run or switches off before the rear is raised to the correct level then the system isn't signalling for air - suggesting a height controller fault/electrical fault/air-sus ecu issue. (as the compressor works and there's no air leak, perhaps this is what the technicians should investigate next) From under the car, they might even be able to push or adjust the controller rods to see if it makes any difference.

There are a few threads on the subject but I couldn't find a complete RX air-sus component diagram.

Useful info from CL

HC test and repair

location and replacement of a height controller

Roger001 · July 15, 2022

I’ve just been into Lexus to check directly with the technician working on the vehicle.

he says he now thinks it could be the air drier on the suspension with blocked filters ?

he’s ordered a new air drier…..

Herbie · July 15, 2022

1 hour ago, Roger001 said:

he’s ordered a new air drier…..

Are they paying for this or are you?

If you're paying I would insist that they bypass the air drier with a short length of pipe to see if that improves the situation, or take out the filter if it's removable, before spending any money.

Neil E · July 15, 2022

9 hours ago, Roger001 said:

I’ve just been into Lexus to check directly with the technician working on the vehicle.

he says he now thinks it could be the air drier on the suspension with blocked filters ?

he’s ordered a new air drier…..

Are they still guessing?

I agree with Herbs and Piers, the tech should be able to test for a blocked line and the air compressor makes a distinctive, obvious and clearly audible whirring noise when it's working. It can be heard in the cabin, easily.

Has the technician actually tested and ruled out a fault with the height controllers or the signal from them to the ECU?