Rear suspension low

Tomtit · July 17, 2021

The left hand rear suspension on my 2002 LS430 drops overnight. It drops a little further after each subsequent night. I have read a number of posts on this forum and I am now wiser for it. I have the Lexus workshop manual.

I have checked the following:-

1. Techstream shows no fault codes.

2. I have sprayed soapy water on the pipe connections at the compressor, rear height control valve and the LH suspension strut. I also sprayed the rubber part of the strut in situ. There are no bubbles to indicate an air leak and I can't hear a hissing noise anywhere.

3. I removed both rear height level sensors and checked their voltage outputs as per the workshop manual. The readings were OK. The sensors were very clean inside with the faintest trace of carbon dust which I removed. The terminal connections were clean. I could not disconnect the sensors at the lower arm as the nuts had siezed. I disconnected them at the other end of the rods. With the LH sensor disconnected from the lower suspension arm I turned the ignition on and moved the sensor arm up and down but the suspension did not raise or lower. As an afterthought, I wondered if the engine has to be running for the compressor to work. I had the car jacked up at an awkward angle to get access and I did not want to cause problems by starting the engine.

4. When I start the engine the compressor will raise the car to normal ride height within about 30 seconds. When I set the switch to high the car lifts by a further inch. From this I assume the compressor and its wiring from the ECU are OK.

I have not removed the suspension strut for a closer look. There is some work involved and I don't fancy doing it in this heat (27 degrees and no shade).

I suspect that I will need another height level sensor or strut but I don't want to throw parts at it and end up spending more than the value of the car.

Any thoughts would be appreciated. Thank you.

steve2006 · July 17, 2021

The outer rubber boot on the strut is not fully airtight it is a dust cover, any leaks from the strut seals would not show using LPF or soapy water on it.

New struts as you are already aware are expensive, secondhand may or may not last plus even those are attracting premium prices now.

Mine had already been converted to springs, which given if one has begun to fail the others tend to follow, is a reasonably cost effective longer term solution.

I think there are also aftermarket coil over kits available too.

I think for now continue to monitor the situation, if the car continues to drop lower overnight and the suspension takes longer than present times to fully inflate then further action will be needed. It’s unlikely to completely fail leaving you stranded but has now fired a warning shot across the bow.

The-Acre · July 17, 2021

You could chance a used one. Removing the rear seat is nowhere near as bad as some suggest, you could do it in 15 mins. Remember the rear struts are handed, unlike the fronts which are the same.

Tomtit · July 17, 2021

Steve/Phil.

Thank you.

The workshop manual says remove the outer dust cover then check the rolling diaphragm for damage. I need to remove the strut from the car to do this. I have no problem removing the rear seats; it looks straightforward. I just don't fancy doing it in this heat. I will leave it for a cooler day. I will read up about conversion to springs. I am reluctant to lose the magic carpet ride but I don't want to spend more than the value of the car just to keep the air suspension.

I know that M.O.T testers don't do the bounce test on shock absorbers nowadays. Does anyone know if a low back end would be a M.O.T. failure?

The-Acre · July 17, 2021

17 minutes ago, Tomtit said:

Steve/Phil.

Thank you.

The workshop manual says remove the outer dust cover then check the rolling diaphragm for damage. I need to remove the strut from the car to do this. I have no problem removing the rear seats; it looks straightforward. I just don't fancy doing it in this heat. I will leave it for a cooler day. I will read up about conversion to springs. I am reluctant to lose the magic carpet ride but I don't want to spend more than the value of the car just to keep the air suspension.

I know that M.O.T testers don't do the bounce test on shock absorbers nowadays. Does anyone know if a low back end would be a M.O.T. failure?

I can't see why a low corner would be a failure if the tester couldn't find an actual fault. Mine had oil misting so it was obvious, although it didn't leak air! Also worth mentioning that detaching the air line is easier on the rears as you have more access. Another thing probably worth a mention is the pre and facelift models share the same struts if you're looking to buy used. There's nothing complicated about removing/refitting the suspension system on the LS430, apart from limited access on the front airlines.

Tomtit · July 19, 2021

Having read many posts on this and the U.S. forums it makes financial sense to fit a new coil spring and shock absorber setup all round. There was a previous M.O.T. advisory for oil mist on the front struts, so I don't know how long they will last.

I would be looking for standard springs and KYB struts to aim for a similar ride quality to what I have now. The parts diagrams show that I will also need ancillaries such as strut mounts.

Can any member recommend a supplier who will charge less than the main dealer? I can fit the parts myself.

Thank you.

steve2006 · July 20, 2021

You will struggle to get the same ride quality as air suspension.

I have these fitted to mine, works out around £1200.00 shipped and duty.

Made in USA too.

https://www.strutmasters.com/suspension-parts/lexus/lexus-ls-430/2002-lexus-ls-430

A set of decent coil overs are around £800.

Or buy all the parts from Rockauto.com

From Lexus you are looking at around £450 a corner for all the bits, top mount, insulator, spring and damper. There are 2 types of front damper one at around £80.00 and the other at £220.00 !

That’s assuming all the parts are still available as stocks for earlier models have been dwindling for some time now.

Tomtit · July 25, 2021

Steve.

Thank you for the information.

I have read many posts on the U.S. forum. One member said that the Strutmasters kit left the LS430 sitting too high. Someone said that the kit would not fit and that Strutmasters wanted a 25% restocking fee. That together with the cost of sending it back to the U.S. could be expensive. I looked at the Suncore Industries coilover kit but someone said that it sags after a while. The kit from American Air Suspension looks good but they only ship to U.S. and Germany.

After a lot of thought I decided to get KYB coil springs, dampers and ancillaries. I have ordered the parts piecemeal from four different sources including U.S. and Japan, and some parts may not arrive until September. For the benefit of other members I will report back when I have fitted them.

The-Acre · July 25, 2021

5 minutes ago, Tomtit said:

Steve.

Thank you for the information.

I have read many posts on the U.S. forum. One member said that the Strutmasters kit left the LS430 sitting too high. Someone said that the kit would not fit and that Strutmasters wanted a 25% restocking fee. That together with the cost of sending it back to the U.S. could be expensive. I looked at the Suncore Industries coilover kit but someone said that it sags after a while. The kit from American Air Suspension looks good but they only ship to U.S. and Germany.

After a lot of thought I decided to get KYB coil springs, dampers and ancillaries. I have ordered the parts piecemeal from four different sources including U.S. and Japan, and some parts may not arrive until September. For the benefit of other members I will report back when I have fitted them.

I fitted the Strutmaster kit and it sits about the height of air suspension on high. I didn't find the ride to be any different to air quite honestly. You will need to remove the suspension system fuse which will disable any warning lights. The actual removal of air and fitting of a conventional setup is very straightforward, all you need is basic knowledge. If you're not intending to go back to air you can simply cut the airlines, especially on the front, and that will save time and knuckles!

Tomtit · July 25, 2021

Phil.

Thank you for the information. I will probably not go back to air suspension due to cost. I have just bought a fuel line disconnector kit which was recommended by a forum member. Using this I should be able to disconnect the air lines without damaging anything. I am patient and methodical and I don't like to cut or break things if it can be avoided. I have not removed the front wheelarch liners yet, so if access to the front air lines is tight there may be the tiniest amount of bad language!

The-Acre · July 25, 2021

1 hour ago, Tomtit said:

Phil.

Thank you for the information. I will probably not go back to air suspension due to cost. I have just bought a fuel line disconnector kit which was recommended by a forum member. Using this I should be able to disconnect the air lines without damaging anything. I am patient and methodical and I don't like to cut or break things if it can be avoided. I have not removed the front wheelarch liners yet, so if access to the front air lines is tight there may be the tiniest amount of bad language!

I didn't remove the wheel arch liners, I used a piece of nozzle from a silicone tube with a slot in the side, obviously the proper tool will make it easier. The air struts are surprisingly light so that helps with removal. Looking forward to the end result. Also if you could eventually let us know the total cost it might help others. I see Rockauto are selling a complete strut assembly for £55 with a two year warranty, but I think the route you're taking is likely to produce better results. It's also a good time to check your front upper control arms as the struts need to come off to replace them.

Malc · July 25, 2021

6 minutes ago, The-Acre said:

to check your front upper control arms

now that too could be an 'orrible cost if those 4 need replacing ...... say 150 - 200k miles longevity on the originals maybe

Malc

Tomtit · July 25, 2021

That is a good point about the control arms. Mine have 140k on them so I will have a look.

At this stage I don't know what the total cost will be as there may be import duties to pay. I will post the final cost in due course. I have learned a lot from the forum and I am happy to help others.

Tomtit · August 18, 2021

There seems to be a shortage of parts in the U.K. I have ordered parts from eBay U.K., amazon U.K., amazon U.S. and Amayama in Japan.

The KYB coil springs ordered through eBay U.K. arrived within a few days. The parts from amazon U.S. arrived piecemeal within a fortnight. The parts from Amayama took about a fortnight. The 2 shock absorbers from amazon U.K. gave an estimated arrival time of 2 weeks. After 3 weeks they still had not been despatched and they could not estimate a delivery date. I cancelled the order and ordered a pair from eBay. They are coming from California and have been despatched.

I had to source 2 rubber boots/suspension insulators for the front strut mounts as they did not come with the KYB mounts. They arrived quickly from eBay U.K.

The parts diagram for the rear coil springs showed an insulator which was not supplied with the springs. The insulator has its own part number but the Lexus dealer said it was not supplied separately and that I would have to buy 2 coil springs to get the insulators. I already have the springs so that was a non-starter. I have now ordered 2 insulators from Amayama. I ordered them during a national holiday in Japan so there will be another delay. Internet pictures suggest that the insulators are only pieces of rubber which fit onto the coils. I have seen them fitted on the second coil down so I assume that they are to prevent the coils rubbing together and creaking during compression.

I probably could have obtained all the parts for the conversion from the main dealer, but at £450 a corner it would work out at double the part-exchange value of the car. I now have most of the parts and I should be able to start work soon. To help others I will make a list of all the parts needed, the prices and where I sourced them. I will also report back on how the job went and how comfortable the ride is.

Tomtit · September 12, 2021

This is a lengthy post but it will hopefully help others who want to convert from air suspension to coil springs and shock absorbers.

The part nos. have been taken from lexus-europe.epc-data.com and are for a 2002 model.

FRONT SUSPENSION

90950-01310 x2 rubber cover. Do not order as it will not fit the support washer on the KYB SM5566 mount.

48680-22050 x2 support washer. Do not order them as they are supplied with KYB SM5566 mount.

90178-10014 x6 nut for support. Supplied with KYB SM5566 mount.

48680-50110 x2 support assembly. Ordered KYB SM5566 from amazon U.S.

48257-22070 x2 bump stop. Comes with KYB SB104 ordered from amazon U.S.

Rubber boot x2 ordered from eBay as not supplied with mount.

48131-50130 x2 coil spring. KYB RG6461 ordered from eBay.

90177-12002 x2 nut for shock absorber is supplied with the shock absorber.

48510-59366 x2 shock absorber. KYB 341392 ordered from eBay U.S.

90105-14153 x2 shock absorber bolt. Ordered from Amayama.

REAR SUSPENSION

48553-50100 x2 cap. Ordered from Amayama.

94130-61000 x6 nut. Did not order. Used existing nuts.

48755-50110 x2 washer. Do not order. Supplied with mount KYB SM5565.

90179-10088 x6 nut. Do not order. Supplied with mount KYB SM5565.

48755-50100 x2 support. KYB SM5565 ordered from amazon U.S.

48341-50070 x2 bump stop.Comes with KYB SB104 ordered from amazon U.S.

48257-50020 x2 rubber boot. Supplied with support KYB SM5565.

48258-50020 x2 rubber seal. Ordered from Amayama.

48231-50170 x2 coil spring. Ordered KYB RG3072 from eBay.

90177-12002 x2 shock absorber nut. Supplied with KYB 341393 shock absorber.

48530-59416 x2 shock absorber. KYB 341393 ordered from amazon U.S.

90177-14004 x2 shock absorber nut. Ordered from Amayama.

Total cost of parts and carriage between £1000 and £1100.

NOTES ON THE CONVERSION

I have not given full instructions as these are available elsewhere.

1. To disconnect the air lines from the struts you will need to make a tool. I used a 1 1/2 inch piece of 8mm plastic tube with a slot cut on one side.

2. You cannot do this job without coil spring compressors. They have to be long enough; my existing compressors were not and I had to buy longer ones.

3. If you are doing the job without a helper (like me) you will need a long crowbar for levering components into place.

4. When fitting the shock absorber/strut assembly a trolley jack under the hub may help to line things up.

5. Rear seat removal is no great problem. Do not be put off by it. Despite what the workshop manual says there is no need to remove the high intensity brake light. There is no need to remove the rear parcel shelf. It only needs to be raised a few inches to access the mount nuts.

6. On the front suspension you will have to split the upper arm ball joint to get the shock absorber out and fit the new one. Be ready to catch the hub when it comes free and tie it up to avoid straining the brake hose. To access the shock absorber lower nut you can disconnect the anti roll bar drop link.

7. The offside lower front shock absorber nut was a challenge to undo. It needed a 3 foot breaker bar and a blowlamp to move it. I am glad that I ordered replacement bolts.

When you have finished, have the wheel alignment checked and inform your insurers about the conversion.

The end result:- The ride is slightly firmer than on air but perfectly acceptable. It is comforting that I will not have to spend many times the value of the car on air struts, height level sensors and air compressor, any of which could fail at this age.

Malc · September 13, 2021

well done, a huge achievement for sure

Malc

Tomtit · September 13, 2021

It was a challenge. The car will not fit in the garage, so I was grateful for the spell of dry weather.

I was surprised at the weight of the air struts. I thought they would be heavier. They were easy to lift out. The most time-consuming part was compressing the coil springs far enough. My existing compressors were not long enough. I bought a pair of Sealey AK3846 long reach compressors. (£23.95 on Amazon). They were not a perfect fit, and at times only 3 of the 4 claws were hooked over the spring. I used my existing compressors as a back up in case the Sealey slipped. The front springs had to be compressed to 29 cms before they would fit. I can't remember the length of the rears.

On the test drive afterwards there were 2 slight problems. There was a knock from the front nearside on uneven ground. I re-checked the torque settings and they were all correct. I then noticed a bit of play between the mount support washer and the shock absorber nut. I ignored the official torque setting and tightened the nut to eliminate the free play. Problem solved. The second problem was a slight judder through the brake pedal for the final few yards. Techstream showed no fault codes. I took out both rear wheel speed sensors and cleaned the ends with PCB cleaner. I checked the reluctor rings for corrosion or damage and they were OK. I cleaned the white corrosion from the holes where the sensors fit. The sensors went in more easily. The original problem must have been a sensor not positioned correctly as the problem has not recurred.

To help others, I wanted to cover these points on my previous post but after a lot of typing I was afraid that I might be timed out and lose all the typing. If anyone contemplating this job has any questions i will be happy to share my experience.

George86 · September 20, 2021

Hello. I hope some of you can help to solve the issue with my LS 430 year 2003.
I park my car afternoon and until next morning the rear left suspension lower then the others, but only the rear left. I have replaced the level sensor on the buttom, but still the same, after a replaced the air strut as well, but still does the same. I have been in a garage they checked by computer, But did not show any trouble codes. If any of you have got any idea let me know please. Thanks you!