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Hi everyone, my first post on here, although I’ve been on here reading plenty of threads before now but still can’t find a constructive solution to my problem! 

Ive had my current ls430 just over a year and it’s a dream but in order to get it through its last mot I needed to get the rear back boxes welded up due to leaks. 

All passed and I thought all was good but now there is an awful droning noise from underneath the car that just fills the whole cabin with noise especially speeds higher than 40mph. 

Took it back to get looked at as I was sure the exhaust wasn’t fitted back together properly but all looks ok. Went to another garage who confirmed this but they also test drove it and could hear the noise but couldn’t pinpoint the problem. 

Weeks later I’ve picked up a used good condition centre silencers and back boxes and had them fitted yesterday and alas the problem is still there. If nothing else I think it’s worse. 

I miss my quiet 430 and wondered if anyone had any experience of this. I don’t fancy a custom exhaust build or paying ££££ Lexus themselves. 

I thank you guys in advance and looking forward to any replies. Please not I am not a mechanic!!

Cheers

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7 minutes ago, Stevofoto said:

Hi everyone, my first post on here, although I’ve been on here reading plenty of threads before now but still can’t find a constructive solution to my problem! 

Ive had my current ls430 just over a year and it’s a dream but in order to get it through its last mot I needed to get the rear back boxes welded up due to leaks. 

All passed and I thought all was good but now there is an awful droning noise from underneath the car that just fills the whole cabin with noise especially speeds higher than 40mph. 

Took it back to get looked at as I was sure the exhaust wasn’t fitted back together properly but all looks ok. Went to another garage who confirmed this but they also test drove it and could hear the noise but couldn’t pinpoint the problem. 

Weeks later I’ve picked up a used good condition centre silencers and back boxes and had them fitted yesterday and alas the problem is still there. If nothing else I think it’s worse. 

I miss my quiet 430 and wondered if anyone had any experience of this. I don’t fancy a custom exhaust build or paying ££££ Lexus themselves. 

I thank you guys in advance and looking forward to any replies. Please not I am not a mechanic!!

Cheers

have you had the wheel bearing checked, droning noises normally come from there especially at speed. 

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Hi, all bearings are almost new. This happened immediately after the back boxes had been welded. 

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You aren't a million miles away from Tony Banks exhausts in Leeds, i'd go there and ask them, they will sort you out i'm sure. Took my LS400 there to fix the usual rusted Y pipe to the Cats, sorted it no problem!

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Hi yoda400 I’ve seen his listings on eBay and heard the good things on the forum about his work. Might be a trip over there at this rate. Cheers

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Did it have covers on underneath and they've not been put back on?

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Droning usually comes from resonators (center box) or cats, if you have changed the resonators and the rear boxes then it must be the cats... you will probably find that welding the rear boxes needed some use of a hammer which has dislodged the honeycomb in the cats and is making the noise... try to knock the cats gently with your hand, if they rattle or sound hollow ( the honeycomb can shatter and get blown out the tailpipe in small bits causing a hollow sound) then they have failed... a decent exhaust shop should find the culprit...

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Try to knock gently not only resonators and silencers for droning sound, but every thermal shield (this thin metal sheets here and there, over the pipes and under the car). Their screws and clips are easy loose a bit after years, especially if anybody works next to them and touches/moves them, and next they could rattle as hell. In fact, I had this problem yesterday, I patched a big leak under GS, car was much quiet now, but she annoyed me immediately with droning (it was masked before by roar of V8). I had to jumped under the car one more time and solid screwed one of the shields.

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Out of interest, what is the life of  430 exhaust. I thought being stainless steel, about 20-25 years. Am I wrong?

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Isn't it only stainless on the LS400? I thought they started cutting costs with later models... Will still be a decent exhaust, but not stainless

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6 minutes ago, Yoda400 said:

I thought they started cutting costs with later models..

Ive heard that as well & not just on here I've also had it from Lexus main dealer & an indi mechanic, the comments were on the car as a whole not any specific parts.

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I think it is still stainless but there are different grades, some of which will corrode well before 20 years.

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I'm sure later models are superb, but no denying the cost cutting. Take a look at the seats for example. The leather usually stays in very good condition on the 400s, but in the 430s you often see ratty seats!

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5 minutes ago, Yoda400 said:

I'm sure later models are superb, but no denying the cost cutting. Take a look at the seats for example. The leather usually stays in very good condition on the 400s, but in the 430s you often see ratty seats!

I think it must be to do with all the tiny holes in the ventilated seats, they surely can't be as robust.  That said, the seats on my 430's were all excellent. Having had two 400's I know it would be hard to improve on the quality of the leather.

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53 minutes ago, ColinBarber said:

I think it is still stainless but there are different grades, some of which will corrode well before 20 years.

This is the crucial point, IMHO. Everybody think Lexus or some aftermarket sources or fabricators delivery bulletproof eternal exhausts, because they are shiny and stainless steel (SS). Yes, they are, nobody lies, this is SS, with small deception. Because what we need (and wrongly presume we got) is highest grade heat-resistant stainless steel. Automotive typicaly use lowest grade SS, very good in room temperature and with some water action, but not with exhaust temperatures and exhaust agressive chemistry. It is slightly better than mild steel, but don't even think about 20yr or more. Good fabricators use any marine grade SS, much better, designed and certified for decades in salty enviroment. It withstand much longer, but still could be nasty suprise in very hot parts, because still - it is not heat-resistant enough or at all.

The problem with real heat-resistant SS is: it is not only expensive, but very difficult to form and work with and insanely difficult to weld. Only applications I remember are aircraft industry, maybe military and some exotic chemical equipment. And this is main reason even car manufactures with such a price tags they could afford any technology, prefere same as aircraft industry - not the best heat-resistant SS, but titanium or similar alternatives.

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9 hours ago, Ben01 said:

Only applications I remember are aircraft industry, maybe military and some exotic chemical equipment

and quite clearly my 1995 Ls400 ....  now nearly 209k miles and going strong ( ly stainless ) and 23 years young

Malc

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Yeah, in early '90 they probably use slightly better steel than 2002. Or 2006. And the south is not so salty as Wales or Scotland, probably.

BTW in late '80 - early '90 even bigger fords (sort-of my area of expertise) got decent exhausts, like good mild steel with aluminium plating. It withstands 20+ years, maybe 30 in no-salty-winter countries. It was common knowledge for big fords technical savvy owners "dont scratch or weld or cut any ori exhaust "silver" parts with Motocraft logo and punch your mechanic in the face if he did it", becouse after welding overheat or grinder, the parts dissapear faster than you say "where did this aluminium plating go?". But this epoch has gone.

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You need to check some of the posts I've listed and commented upon.

There is a Polish Ebay selling German made LS430 exhausts delivered to your door for circa £150.

A couple of guys on this forum including me have had them fitted - waste of time getting the old one welded at this price!

 

 

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