Vibrating noise in cabin

[Razor61]

A couple of weeks ago my wife mentioned a vibration/rattling noise in the cabin while driving her 2010 IS250.
I drove the car and there was indeed an annoying noise coming from behind the dash on the drivers side, or so it seemed. Noise was more evident when cruising/overrun and in hindsight was a clue. Spent a bit time trying to figured out what was causing the noise, aircon off/on, trying fan speeds, audio on/off and lots of other tests. Nothing found so because the car is under extended warranty I booked it in for Tuesday at Lexus Bolton. Although it’s under warranty there is a diagnostic charge and if it’s a part that’s faulty the diag charge isn’t charged. Agreement with Lexus was that I try and figure out what was causing the issue and it’s not a problem removing the drivers dash trim to try and diagnose it.
So today I spent some time looking at the issue ‘properly’.
Went to the car armed with spanner’s etc to start removing the lower dash trim and start looking, before I began I started the engine and from outside stuck my head in the drivers footwell and revved the engine. Noise wasn’t from the behind the dash but from underneath the drivers seat.
Checked under the seat, checked seat bolts and for anything that could be vibrating. Couldn’t find anything.
I then did a Google search for the noise under the seat, I found a post for a GS250 about a metal plate under the car with loose bolts, directly under the seat causing a very similar noise.
Armed with this info I had my wife sit in the drivers seat and rev the engine up and down while I looked underneath and pressed/held various bits. When I reached under and held the heat shield on the exhaust the noise stopped. Repeated a few times to make sure, next step was to get the car on the ramps and have a good look.
Car on the ramps, looked underneath and found an exhaust heat shield clamp broken. Took it off and started the engine, repeated revving and no annoying noise.
I would have sworn the noise was coming from inside the cabin and underneath the drivers seat, I could hear something outside underneath but nowhere near as loud as inside the cabin at all. Just shows how car noises can deceive and the cause can be outside but the noise is heard inside.
 

[normski2]

This has occurred before with a few folk on the forum.

Well done for having the sense to have a look first for your own peace of mind. It nearly always pays to investigate problems yourself in the first instance!!

[Razor61]

9 hours ago, normski2 said:

This has occurred before with a few folk on the forum.

I did find this post and the noise in the video is the exact noise. Noise is a lot louder in the video though and in my case was there at higher speeds as well but noise goes when accelerating. Loose exhaust was mentioned but discounted and I can understand why as it sounds like inside the cabin not outside or exhaust, when sat in the car. Even outside you can’t hear much with the car on the ground, maybe because the exhaust is tucked in the transmission tunnel. If the car was on a ramp and you were stood directly underneath it would be obvious I guess.

https://www.lexusownersclub.co.uk/forum/topic/136384-lexus-is250-rattle-under-steering-wheeldashpedals-when-driving-slow-video/

[Mr Vlad]

Must admit Paul your post made me giggle a bit. Yes it's a phenomenon how sound travels. How long have you had the is250? How do you find Lexus Bolton to use? I use Stockport and both are equidistant to me just about. 

[Razor61]

1 hour ago, Mr Vlad said:

Must admit Paul your post made me giggle a bit. Yes it's a phenomenon how sound travels. How long have you had the is250? How do you find Lexus Bolton to use? I use Stockport and both are equidistant to me just about. 

Glad it made you giggle😄
I think the noise was getting into the cabin via the transmission tunnel and maybe then through the heating ducts under the seat......who knows.

I find Lexus Bolton excellent, I used them 2003 to 2007 for a company IS200. When I got my first 95 LS400 3 or so years ago I used them again and still do for my current LS400 and the IS250.
There are a couple of mechanics/technicians that know the LS400 and know their 'stuff' on them and is very important for me.

[Razor61]

1 hour ago, Mr Vlad said:

How long have you had the is250?

Had it for just over 2 years, bought remotely from Lexus Wolverhampton with 3 years warranty.

[Razor61]

Update on the broken exhaust shield clamp, yes I could just leave it off or use a large jubilee clamp but I decided to buy the genuine OEM clamp.
Cost for 1 x clamp approx. £25 plus the bolt at probably £2 and there are 4 of them. If one clamp has rusted and broke then the other are likely or could follow.
So I ordered 4 x clamps and 4 x bolts from Amayama for £37 delivered with no duty or tax to pay on that amount. £10 more for the extra 3 x clamps and 3 x bolts.