400fanboy

Originally posted here, and on reddit and I'm sure many other places. Originally written by [unknown], Updated by 400fanboy Mar, 2024.

Disclaimer: I'm not a professional mechanic nor do I work for Lexus. I'm just an enthusiast who loves these cars, obsesses over keeping them on the road in good condition and is learning how to DIY. These cars are quite easy to work on as they are designed intelligently, as a Toyota should be, even one as complicated as this.

If I may preface two items here.

1) Do not buy aftermarket parts for this car. Almost universally, they are a cost-down version and make huge sacrifices in quality to achieve that. This is doubly important for any seal or rubber component. It's not like a Toyota Corolla. It's very common to replace something with some aftermarket thing from Autozone, only to be back replacing the same thing only a couple of years later. Every aftermarket part I've put on my car has failed me. Fan clutch, shock mounts and brake rotors, in some cases nearly instantly. This has yet to happen with any OEM part. However, sometimes you won't have a choice because as good as Toyota is, parts availability, especially for early LS400's, is becoming difficult. So you won't have a choice for some items. Amayama and Lexuspartsnow and several online dealership parts counters are the 3 places I find my parts.

2) There are three types of cars which are available. A) Are ragged cars with any number of miles, usually high, run on deferred maintenance, running for better or worse like just a normal cheap car. B) Cars owned by old folks, original or second owners (often flipped by dealers on auction sites), usually with very low miles which appear attractive. Many of these are still on all-original parts. They may have been sitting for years before behind sold if they are part of an estate, and more often than not are on the verge of needing a ton of work to bring it back to its former glory. An "all original" 30 year old car means it needs $2000-5000 of deferred maintenance. C) Enthusiast owned cars that have already been gone through, with these major service items addressed as they came up. These are very rare to find, especially a all-stock unmodified example. Almost all LS400's fall into first two silo's.

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POWER STEERING

This warrants it's own sections as it's one of the biggest issues with these cars, especially the first generation ones. The main issue is that the pump will leak on almost all cars, and conveniently leak onto the alternator, frying it and leaving you without power. Make this the first thing you check on every car. First generation cars can also leak from the power steering reservoirs onto the alternator, or from the hose to the reservoir in 98+ cars. Also, if power steering fluid level drops but you don't see a leak, or if there's a puff of white smoke on startup, then you have a leak from the idle up valve that uses vacuum to raise the idle when the power steering pump is operated. It's screwed in to the pump and has two vacuum lines coming from it. It can be very difficult to replace with the pump still on the car, so if you ever have to remove the pump, make sure to replace this part and the hoses that lead to it!

ENGINE

Timing belt and water pump. They should be changed every 100k miles or 10 years, though many cars survive to see double that. Cue the endless internet debate on how long you can run a timing belt. There is a sticker under the hood, usually on the engine cover. 90-94 cars have a non-interference engine, meaning that if the timing belt jumps or snaps, your engine will just die but no mechanical damage will occur. 95+ engines are interference, so loss of timing will cause the pistons to hit the valves and result in catastrophic failure. When buying a 95+ car then timing belt change becomes more critical. Make sure you buy the whole kit and replace everything. Tensioner, idler, water pump, etc.

Cam seals and the crankshaft seals have a tendency to leak. You will notice by seeing an oily mess on the front of the engine, coming from behind the timing cover. In bad cases it will even drip on the ground. It is normally suggested to replace these while doing the timing belt and water pump service, it's not that much more work to address it then. 98+ cars require the cams to be removed, so preventative maintenance here is not recommended. Address it when it comes up. 98+ also have a seal in the VVTi gear that can leak. I've had to do all three in three separate occasions (read: labor $$$$) because I was being a cheapskate and the shop I used wasn't keen on "while we're there" maintenance.

Valve Cover Gaskets. These usually start to go around 80-150k depending on your luck. You will notice by a little wetness around the valve cover itself, or in really bad cases by dripping towards the rear of your engine. If it's really bad it will leak onto your hot catalytic converter releasing a puff of smoke when you're at a standstill. You can also pull a spark plug and see if it's oily as the spark plug tube seals usually fail at the same time and should be replaced as part of the job. These are very commonly overlooked and replaced with ****ty aftermarket junk! Make sure to do them and use OEM.

Ignition. 98+ cars use coil pack ignition, and I would recommend not addressing these at all unless they fail (which is very rare). However, earlier cars use distributor iginitions, and by this age, failures will be common and may cause drivability issues. If it hasn't been done, I would expect it to be on the list.

Vacuum recovery box. There's a plastic box along the intake tube that goes from your air filter to your throttle body on the 98+ cars to which several vacuum lines attach. The nipples for these lines are made of plastic and snap off on most cars, resulting in people jerry rigging hoses with RTV (I've even seen electrical tape!). You can check this easily by just removing the engine cover and taking a look. This can cause vacuum leaks and should be addressed. You can buy barbed brass fittings at the hardware store, drill out the hole where the old nipple was to enlarge it and screw the fitting in, putting some RTV around the joint for safety. Be careful not to crack the plastic in the process as it's very thin. Depending on the model and year of your car, you can still order new runs online. Though this window is quickly closing. The PCV valve is also part of this system. Replacing it, while simple, can prove to be hard as the grommet is extremely difficult to remove. An xacto knife, a variety of your pliers and patience to are your friend here. Be careful you don't drop it into the valve covers!

Hoses. Check them to make sure they're soft. With the age and heat most of these have gone hard and brittle. If you ever work on your car and plan to remove a hose, make sure to buy a replacement as it is very likely to split when you remove it.

Serpentine Belt. On high mileage cars check the tensioner and idler pulleys and make sure there's no bearing noise. They're cheap and easy to replace so I suggest doing it next time you change your belt on a high mileage car.

The fuel injectors are bulletproof, but 98+ are air-assisted and the passage can become choked with carbon. This is a service which is almost never performed and can make a big difference:
https://www.clublexus.com/forums/ls-...ttle-body.html

SUSPENSION

Strut rod bushings, every 100k miles. Symptoms are: clunk when you first tap the brakes (you'll hear it in parking lots), slight vibration when going 60-65 mph or a shimmy under light braking from highway speeds that will be felt in the steering wheel instead of in the pedal like warped rotors normally would.

Lower ball joints, every 100k miles. They're heavy cars and wear them out faster than other models. If they are leaking or torn, obviously, they need to be replaced. However, they can be worn out even if they are not visually degraded or have excessive play! The car may have excessive body roll in corners, may be "vague" in the front. The car will be sensitive to crosswinds on the highway and want to tramline in the road grooves. You may have a loose steering column which you can hear clunking when you go over certain types of bumps. If you grab the steering wheel at 12-6, can actually move the entire wheel\column and hear that dull clunk. You may have any combination of these symptoms, or maybe others not documented here. They are a very easy replacement and are not expensive and can totally transform how the car drives, and IMO are one of the most transformative repairs you can make on any LS400 which hasn't had them replaced recently.

Shocks: If you plan on replacing the shocks, this is a great time to replace the upper control arms as the shocks need to come out to replace them. Lots can be said here. Many people want lowering springs or full coilovers, and there are mild options which retain some (but not all) of the stock glide. Tradeoffs must be made. If you desire a firmer\tighter ride\handling, you will be surprised how much stiffer and tighter a car with blown suspension gets when you refresh back to OEM. A word about parts - KYB is a common aftermarket replacement shock for the LS400. The product is good. While KYB also makes the OEM shocks, it is not known if the ones in the KYB box sold at Autozone are made to the same standard as the ones in the Lexus box. Whether you want to pay the Lexus premium is up to you. Make sure you also replace the insulator (aka boot), shock mounts and bump stops while you're in here. Buy OEM parts for these accessories, do not save a few bucks by getting aftermarket parts and they all do need to be replaced at the same time as these age at the same speed as shocks.

Air suspension: Good luck if you want to keep it working. As air suspension systems go, they seem to be quite robust. But they are old systems and parts are extremely expensive now (if they even exist). There is no penalty or difficulty reverting to standard suspension once the air suspension breaks.

And at the age of these cars, you can include every other bushing as well.The front has an upper and lower control arm with several bushings. The rear multi-link has 5 bushings per corner, with one tie-rod like end. Two bushings are pressed into the rear knuckle and are unavailable for all LS400's. And of course there are sway bar links\bushings. As would be expected, replacement of these can return a lot of new car tightness.While the LS400 is very soft, it's by no means imprecise or difficult to keep straight on the highway.

The driveshaft has rubber in it too and we're starting to see these rotting away. There are two major items. The center support bearing, which requires complete removal of the driveshaft from the car thankfully is not too common of a wear point. But the flex discs\guibo's are a very common issue as these cars are 25+ years old. There are two, one on the trans one on the diff. They all will have lots of hairline cracks as they age, and may present driveline slap or minor vibration in certain speed ranges.

ENGINE AND TRANS MOUNTS

These have a big effect on the ride quality in the car. A bad transmission mount can show itself in many ways. Here are some: a phantom like vibration you feel when accelerating through 1800-2000 RPM. It's a kind of flutter sound, similar to when you go high speed with the windows open but will be very difficult to discern and your passengers might not even feel it. You can also put your hand on the shifter and if you feel a vibration in that rev range or during acceleration, it's probably shot. You may also feel a clunk or a thud under acceleration from a dead stop. This comes from the driveline being loaded with torque from the engine and physically moving the entire assembly.It costs less than $100 and takes 30 minutes to change so there's no reason not to.

Engine mounts are more of a pain and I used a shop for mine. The 1UZ should be able to have a glass of water put on it's intake manifold and show no ripples. Other than the torque of the engine twisting the car slightly, you should not be able to feel the engine if you rev it to redline in neutral. The allowable tolerance here is zero. The car may idle smoothly, but you will feel vibration before 2000rpm if they are shot. These can make a BIG difference to the overall smoothness and roughness and glide of the car. All three of mine were split in half at 145k when they were changed. Additionally, on 98+ cars, excessive movement of the motor from broken mounts can lead to the feed hose for your power steering pump from the reservoir tearing, dumping the contents of the fluid everywhere.

TRANSMISSION

The transmissions on these cars are very solid. Failures are extremely rare and usually are coupled with abuse.

The biggest misdiagnosis is actually the fluid level, the transmission is quite sensitive to them. It can cause all kinds of problems, including no shifting. The correct procedure is to measure the fluid level is: with the car warmed up, having been driven (or at least the gear selector used), with the car on and on level ground. Measure the hot level.

On the first drive of the day, it will hang in 2nd gear up until around 2600 RPM even if you're easy on the throttle then slam or slip into 3rd. Just once. Afterwards it will never do it again. All 1UZ Lexuses I've driven do this and the consensus seems to be that it's normal.

Be mindful of the condition of the fluid. This does cause accumulated damage over time and you may experience harsher and harsher shifts and inconsistent shift quality as the transmission ages. You should have high standards for shift quality. Transmission flushes should be the last resort to save a transmission, normal maintenance is to drain and fill the pan regularly with T-IV fluid. 2 quarts, I do it once a year.

ELECTRICAL

On 90-97 cars, the ECU capacitors tend to leak causing all sorts of crazy issues. The most common ones seem to be hard starting, transmission not shifting, unstable idle, ECU not communication and many many others. Problems will often be intermittent at first and be puzzling as they cross through many separate systems. The ECU can be rebuilt quite affordably by a specialist either by mail-in or locally if you live around one, as only about a dozen capacitors need to be re-soldered. The worst model year is 1997, as that was the first year of the immobilizer combined with very common ECU failures. If you fail to repair the ECU, you now must migrate this to a new ECU. 98+ ECU failures, while still possible, are much less common and they also have the immobilizer problem.

Here is the megathread with info on it:

https://www.clublexus.com/forums/ls-...capacitor.html

And here is how you check it without removing it from the car:

https://www.clublexus.com/forums/ls-...-by-yamae.html

The instrument cluster has two main failure modes. The CCFLs on the needles can go out, leaving them dark, or the Speedometer and/or Tachometer needle will be stuck at zero. Both can be solved by sending it out for rebuild. There are several places in the US that offer this service for the LS400 for between $150 and $300.

Corroded grounds can give funky electrical issues, including a no-start condition where the starter will click once then the whole car will just go dead as if there were no battery plugged in. It will usually start and work properly after pulling the negative battery terminal for a couple of minutes then connecting it back. I had the intermittent no-start issue and replacing all parts in that thread cured it after a relatively straightforward fix.

The starter motors usually don't give people trouble until they age out and fail outright. Failures seem to be more common on later model cars. It's listed here because it is quite expensive to replace because it's buried in the v of the engine. The intake needs to be removed to replace it, the book time is something like 8 or 10 hours.

Coolant temp sensor does what it says on the tin. May become inoperative or sluggish as it ages. Most commonly affects MPG, power output and overall engine profile. OEM part is $20 and it takes only a couple minutes to replace.

https://www.clublexus.com/forums/ls-...ange-pics.html

INTERIOR

The steering wheel tilt motor commonly fails. The steering wheel should move up and away from you when you turn the car off, and return to it's set position when you turn the car on. They can be noisy. And failures seem to be more common than is ideal, sometimes it's a internal gear which fails sometimes it's the motor. Lots of info here:

https://www.clublexus.com/forums/per...ng-repair.html

Audio. There are no "harness" kits for cars with optional navigation (97+). The only way to get modern audio is either a bluetooth radio, a cassette adapter or a full standalone custom system. The 4th unsung option is to delete the navigation completely, but this requires the HVAC and radio from another LS400. Cars without navigation have reasonably standard ways of updating the audio.

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Final notes. If you take care of these cars, they will take care of you. You will notice that virtually none of these items are "leave you stranded on the side of the road". Only two of them are, the power steering and the starter motor. And neither of these come out of nowhere, they will both present signs before becoming a problem. This is one of the reasons why these cars just keep on going and going and going. Everything addressed here is about optimizing that experience.

Thanks and hope this helps!

400fanboy

Let me know if if I missed something or got it wrong. I probably have. Let's make this the best it can be!

timmy0tool

iTrader: (7)

i think the closest thing the UCF30s (LS430) have to the LS400 is the engine, but having a larger displacement, thus the same criteria you shown here would still apply. that's really it. UCF30s have different suspension geometry, making their parts incompatible. Brakes are different, wiring, interior, body panels, etc are different and overall they have different quirks specific to the generation. to me the LS430 is a new platform altogether.

400fanboy

That's fair, line removed

Stroock639

interestingly in terms of the engine and transmission the LS 430 has more in common with the 1998 LS, than the 1998 LS has in common with 1997 and earlier LS 400s... but yea a different story with the rest of the car

the rear brake rotors on the 1998 LS do actually have the same part number as the rear brake rotors on another 90s toyota product, the MK IV Supra!

timmy0tool

iTrader: (7)

it's fascinating to see a 3UZ in an LS400 due to the commonalities!
https://www.clublexus.com/forums/ls-...nto-ls400.html

windsorvr

Random note on the idle up valve for the power steering pump- I replaced my power steering pump with a brand new OEM unit bought from the dealer august 2023. Pump came with the idle up valve port already plugged with a bolt that had some kind of orange thread lock. Not sure if that's an update/revision but it's how mine came. I was going to delete it anyway so it saved me a bit of time. I can't tell the difference between with or without but I rarely drive the car.

400fanboy

I don't like cranking the wheel while not moving either (I always roll a little bit to make it easier on the PS pump), so the assist it provides then is a pretty useless feature to me as well. Just added complexity that will inevitably leak. I will most likely blank mine off as well if I ever address it.

razor61

Great post, it's very helpful, honest, practical with 'real world' advice based on experience.100% agree to only buy OE parts if available and not aftermarket, no matter what it is.

Regarding replacing shock absorbers with KYB or Lexus KYB manufactured shocks. I rebuilt all the suspension on my 98 LS400 with Lexus OE parts but fitted KYB shocks. I figured KYB make the Lexus OE shocks so all should be good.
That was not the case, there is a difference between the KYB shocks and the Lexus OE 'KYB manufactured' shocks, differences listed below.
After 12 months I replaced all the KYB shocks with Lexus OE 'KYB manufactured' shocks to bring back the smooth ride qualities and fix a weird 'bouncy' ride over 'less than good' road surfaces.

Quality:
Lexus OE 'KYB manufactured' shocks are better quality, the bushing at the bottom is a lot bigger/wider/stronger and iirc the shock itself was wider and just felt better and stronger. When I removed the KYB shocks after 12 months the bottom bushes were detaching from the shock 'eye' at the bottom. And I did fit the KYB shocks correctly, tightened the bushing bolt with load on the car.

Performance and ride quality:
The KYB shocks are stiffer and improves the handling quite a lot, it really does, if that's want you want. I wanted the factory smooth ride and 'softness/smoothness' driving over 'speed humps', fitting Lexus OE 'KYB manufactured' shocks brought this back.
I had a weird bouncy effect on a lot of road surfaces with KYB shocks, sometimes my knee/leg was bouncing up/down and I could see the passengers head bouncing up and down. It's not easy to explain but it just wasn't right and was really annoying. Again, fitting Lexus OE 'KYB manufactured' shocks resolved this.

400fanboy

Interesting. So you did shocks twice, and noticed a difference in the ride quality between aftermarket and OE. Thanks for contributing!

I was going to say that all new shocks should feel stiffer than tired, old or potentially broken old shocks. But you did a new comparison on both! Very interesting. I will say that the front of my car is quite stiff but I'm not too spiffy about it - especially after I just solved a ride quality issue with the rear.

There is a lot of subtle stuff that goes into the feeling of a shock. I replaced shock mounts and got a improvement in ride quality, the same bumps are still there but they somehow are significantly less severe. The magnitude of the energy entering the cabin is dramatically lower and the car feels like it can absorb such a wider variety of **** the road can throw at it.

razor61

Yep, I'd spent a lot of money renewing 'all' the suspension front and rear. I did all the work myself and below is my story
I started with the front and planned to do the rear at a later date, took the car for alignment but this couldn't be done because the rear camber bolts were all rusted/corroded and seized (very common in the UK due to the climate and salting/gritting the roads). This forced me to do the rear quicker than I planned, which I did apart from the rear shocks and mounts etc. Reason was that I had 'read' that the rear shocks are a pain to remove and the springs needed to be compressed on the car to remove the rear struts so decided to do that later - approx. 6 months later I discovered that the rear struts can be removed no problem at all - without compressing the springs on the car.
So there was a gap of about 6 months before I fitted the KYB aftermarket rear shocks, this is when the weird 'bouncy' thing started. I read and was told that fitting aftermarket shocks causes an 'odd' ride on the LS400. After a few months I could not live with it and it just wasn't 'right'.
New rear Lexus OE 'KYB manufactured' shocks ordered and fitted, the weird 'bouncy/odd' ride disappeared but that meant I needed to fit new front Lexus OE 'KYB manufactured' shocks so all shocks matched and were correct. This I did so all shocks are now Lexus OE 'KYB manufactured' shocks. That was all done 18 months ago. The ride is 'as it should be' and smooth riding over speed humps/bumps (of which there are lots and lots of in my area in the UK) without needing to slow to a crawl. I didn't like the stiffer suspension because of the harshness over speed bumps, may sound a bit silly but when you live in an area with lots of them and have to slow to a crawl over them it's a Royal PITA and very annoying.
The better handling was a bonus but not worth the odd ride and speed bump thing. Of course the handling is a lot better with the new Lexus OE 'KYB manufactured' shocks, old shocks were 'way' past their best and the car was was 'wallowing' way too much, even for an LS400 but not leaking.
As you know, shocks and suspension wears gradually and owners don't notice or simply don't do anything about it until a garage or 'tester' (MOT in the UK) detects leaks. It's not until someone else drives the car that worn shocks and suspension becomes apparent, I drove my fathers Mercedes C230K a few years back and the shocks were pretty bad and so was the rest of the suspension. I told him this and he had simply adjusted over time to the difference and it was 'normal' to him. He had all the suspension done and said it was like driving a new car.
I have created my own 'draft' buyers guide for the LS400 and is attached. Some of the stuff is related to common rust/corrosion areas that UK cars suffer from and probably US 'rust belt' areas.