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Well it looks like Osaka have found the problem to my really odd vibration.  

The off-side top-cap has gone, and so that does explain why vibration started at about 15mph, peaked at around 35mph, and then came back with a vengeance at 70+.

Scary thing is at any time (say on speed humps) it could pop the shock off the mounting, and hey presto one big mess. Scares me that I took the LS up to the Lakes two weekends ago!!!!

Been told a new part is £190, and on back order (I guess not a common failure).

If I had thought just to pop the rubber caps off, could have spotted it myself.

Photo attached. (That split goes all the way around)

Given I had two tyre places look at my car in last 6 months  -and I said can you check to see if all the front suspension is okay, and neither found any problems!!!

What is odd is that the top plate was likely to be failing at the time Osaka put new front shocks on, but even they could not see a problem with it 6 months ago, and this odd vibration had been happening for about 8 weeks before I got new shocks.

Just waiting for Osaka to see when they can source part, not sure if I should look at Amayama, but if someone can let me know part code for Mk4 LS400 model might see if this is quicker option.

Now need to get used to driving the wifes Mazda 2 for a while.

Top Mount Split.JPG

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That looks like its missing a split pin?

The rubber Cap on my Car over the front springs in theEngine bay both have holes in the top. Not sure that they would make any difference to the ride / vibration etc??

I just glued a couple of Window suckers over the holes.  If its only the circular panel and rubber surely a breakers yard is the way to go?

Perhaps I misundertand this thread.  (Wouldn't be the first time!)

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Pete. Not wishing to put a damper on this "no pun intended", and I hope I am wrong, but I fail yo see how the top mount can cause the vibration. I do agree the mount needs changing, but i would be concentrating my search area to the wheels, and tyres. I would imagine you have already had the wheels balanced off the car. Are there any bulges or misshapes on the tyres? is there any buckle on the wheel? are the bearings in good order? Have you tried swapping wheels from front to back?

I have had a vibration on a car some years ago on a BMC 1800 that only appeared when towing my caravan on a long uphill incline. It never occurred at any other time.
I found the fault by accident when replacing the front discs. I noticed the drive shaft boots were perished "not holed or split" so I decided to change them while I had the front end in bits.
On taking the drivers side boot off the CV joint was dry of an sort of grease just a deposit of graphite looking material. I cleaned, and re-greased the CV joint, and the vibration disappeared.
Under heavy load the CV joint was getting warm, and expanding making the balls tight in there tracks 


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Thanks for thoughts so far.

The team at Osaka have prodded and used pry-bar on all the bushes, checked wheel bearings, and other things.

The vibration I get is from the side of the car that the vibration (and clunking) is coming from, which is why two other places went around with pry-bar and said all bushes fine.

It is the top mount that has failed [my posting title a bit mis-leading], (which according to Google is not good!), and the signs are shown by the split at the top, due to stress on the rubber (I assume).

If replacing this does not cure the vibration, I have been thinking about changing to a GS450h or some such, but would really like to keep the LS for another 5 years (to celebrate its 25th birthday if poss).



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As said in my previous post I do hope I am wrong on this, but replacing the mount should at leased cure the knocking.
The LS400 is a beautiful piece of engineering. I do not know if you have driven a GS450H, but strongly suggest you do even if your not ready to change yet. The 450H is on another level performance wise while keeping rely surprising levels of fuel economy along with great comfort.


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48 minutes ago, Britprius said:

I do not know if you have driven a GS450H,


Not driven one yet, but am tempted to try one next year, seem like there are some decent ones around for £4K-£5K.

My missus will give me grief if I do buy one, given the money spent in last year on LS (though to be fair given the price I paid and the money spent on it in last 6 1/2 years - still only coughed up around £5K for a luxury barge).


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Part numbers are as follows

Support Assembly (The bit with the threaded studs which pass through the inner wing) 48680-50100 £100.00

Bumper ( The rubber bit that slides onto the shocker piston rod) 48331-50070 £30.00

Insulator ( the part that has failed I think) 48157-50010 £40.00.


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Looking at Amayama the earliest delivery is 24/12/2019 and by the time you have paid import duty/VAT I would be thinking of getting one from Lexus here in the UK, maybe try our forum Lexus dealer or Lexus Birmingham.

I don’t know where the £190.00 price came from as this is still very expensive even if it included an hours labour for fitting!

Even with the insulator gone all you have is metal to metal contact the strut itself is still firmly attached with the 3 mounting studs, top nuts and centre nut so it cannot just come adrift.


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On 12/9/2019 at 12:43 PM, Cotswold Pete said:

but if someone can let me know part code for Mk4 LS400 model might see if this is quicker option.

As far as I can tell, the part number for your failed top mount is 48680-50100 and is the same for both sides, if one side has gone then the other may be on it's way out as well.

The other bits, Bump Stop 48331-50070 and insulator/rubber boot cover 48157-50010 may need replacing if they are deteriorated, this will become more apparent when the strut is removed and disassembled.

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Having a soupcon of the Scot in me, I seem to recall that the rubber protectors on my rear Dampers were pretty shot and when the Springs were replaced I gave my mechanic a pair of these and asked him to cable tie them to what was left of the originals.   Did the job fine and saved a few pennies.

(Ps Can't recall if it was exactly this gaiter or another of similar shape and size)

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17 hours ago, runsgrateasanut said:

Having a soupcon of the Scot in me,

Thats a darned good trick, might need to use that - my rear shocks likely to need sorting in next year, and the protectors do look a little past their best.


18 hours ago, Razor61 said:

 if one side has gone then the other may be on it's way out as well.

When the other one starts to go, I now know the signs, and so prefer to just get the one done for now and then be listening out for the nearside failing.  With the car at 206K, expecting the UCAs to need looking at (given the rears were done 50K ago) in the next couple of years, so expecting to be spending a few bob over next few years.. 

Having been driving around in the wifes 2 year old Mazda 2, (which would have been £17K brand new), makes me really appreciate that spending money on a 20 year old LS is still worth it, but at this time of year money a bit tight (as missus likes to do these Xmas trips, so off to Gdansk to get cold for a few days). 

On the other hand I might be tempted to try a GS450h, or a 460 and see if I am prepared to let my love affair with the Mk4 finish.

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