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Air Suspension Problem


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#1 wacko

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Posted 17 September 2008 - 03:29 PM

Hi

My 2005 LS 430 has suddenly developed a very soft rear end. This happened over the period of a week. Dropped some friends off at the airport, 2 adults and 2 suitcases, on the trip there it was fine a week later when I picked them up the rear is all over the place.

Pushing down on the back of the car three or four times can make the suspension travel 100 to 150mm with very little effort. When released the rear will continue to bounce 2-3 times before stopping.

All of the height sensors on the car have been checked by Lexus and they say that they are ok.
The ride height is correct front and rear and the car still self levels and will rise to the hi position and return without a problem.

On the road the back bounces even more especially on uneven roads and over speed bumps. Sport mode when driving seems to make the ride firmer but the back end still bounces. Changing the suspension to sport mode has no effect on the rear of the car when I bounce it by hand.

If it was a normal car I would say that the dampers had gone.

So here are the Questions.
Do air shocks have hydraulic dampers? I have looked under the car but see no evidence of a leak.
How does the damper change from normal to sports mode?
Has anyone else had a similar problem?
The car has 62000 miles on the clock and I have only owned it since July this year. Itís booked in for a full check over at Lexus; it will take 2 days due to the rear seat and aircon having to be removed.
The car was purchased from a Lexus dealer with a RAC inspection and has a 12 month warranty, but as it's shocks they may just say that it's wear and tear.

Does anyone have an idea how much to have the struts replaced by Lexus. I know it will be expensive, but how expensive.
If the cost of replacement is too dear how difficult is it to replace the struts myself and where would you order the struts from.

Any help or advice appreciated.

Thanks in advance.

Mark

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#2 Matrixabc

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Posted 17 September 2008 - 06:55 PM

Hi Mark,

I have just replaced one strut on my LS430 (2001) myself as it had a leak.

in answer to your questions

the air bags do not have any hydraulic dampers they are basically an air bag or bladder, and a week spring inside , they are pumped up , and the ride hight is controlled by the ride hight sensors, the two rear air bags are controlled independently, so technically one could go flat and not affect the other. if you had a leak on one then that side would lower over time, mine dropped 30mm overnight. it turned out to be a small leak in the air bag.
they change from normal to sports mode by turning a small needle in the top of the strut by 90 degrees, it is supposed to stop a bypass valve (not quite sure of the operation).

I did put up on here the costs of replacements, Lexus wanted to charge £600 for one strut. I managed to get one for around £480 from "cheap Toyota parts"

if it went suddenly then i think it must be a control problem possibly the common three way valve feeding the rear air bags. does the other side react when you push down? as i said they should be independent, and when the ignition is off there will be no control at all, and all the valves locked shut.

the air bag is just an "air bag" which rolls over the outside of the strut, the shock absorption is controlled by the amount of air in the bag and the strength of the air bag walls.

is it possible that the air is being pushed from one strut to the other? when you lower the suspension the air is released through a common valve to the front of the car where the air compressor is , which is behind the drivers front headlight.

I was told repeatedly that the air bags are very reliable and they have have had very few failures. if they fail it is usually down to an air leak. I didn't think they could wear out (im sure some one will correct me)

If you jack the car up you can see the air bags and a dust cover around them.

Let us know what you find.

Regards

Alex.

#3 Haylands

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Posted 17 September 2008 - 06:57 PM

Mark

Sounds very odd to me.... why would both struts have the same fault at the same time.... I'd put my money on the ecu for them... anyway see the below it will answer some of your questions.

I have heard that the struts are about £1000 each but it maybe an exageration....

Posted Image

Good Luck hope you get it fixed soon, let us know what it was. I don't think you could call a failing strut fair wear and tear with that age and mileage....

Pete

#4 Haylands

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Posted 17 September 2008 - 07:00 PM

Alex

Sorry, posted at the same time as you.... good to hear they can be got cheaper... but as I said I'm with you it must be control not strut failure

Pete

#5 wacko

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Posted 18 September 2008 - 06:18 PM

Hi

A quick update.

Both rear suspension struts are faulty and need to be replaced. :tsktsk:

It's not a leak of the air bag but some internal fault.
Don't have the full details yet, Iíll get that tomorrow when I pick up the car, it may be Saturday depending on parts delivery.

The garage say they have never see a fault like this on any air suspension equipped car. It's normally a faulty sensor or at worst a leaking air bag. They also don't understand why the both seamed to failed at the same time.

The good news is that the replacement cost will be covered by the warranty :D .
Thatís fine by me. I've be told that the replacement cost including labour is not just expensive but ludicrously expensive.

I also get to drive an IS 250 SE-L around for another day. It's a nice car for throwing around town and playing with the floppy paddle gearbox. But I canít wait to get the LS back and go for a silent cruise.

I'll update this if I get any more information from Lexus.

Mark

#6 Matrixabc

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Posted 18 September 2008 - 06:47 PM

How unusual,

thats like getting two punctures at the same time!, lucky you have warranty. strange that both should suffer internal faults at the same time.
please let us know the outcome.

Regards

Alex.

#7 wacko

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Posted 19 September 2008 - 03:03 PM

Hi

Picked the car up from Lexus today.

Unable to speak to the technican who did the work on car. The only information was from the job card which said faulty dampers.

Massive difference to the car, the back of the car is now nice and firm on the road but still comfy.
The difference does make the front feel a bit soft, but that could just be down to the before and after feel of the car.

i'll see if it settles down in a couple of days. But it's possible its just me.

many thank for the replys to my original post.

Mark

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