Under Bonnet rattle

martslexus · August 25, 2016

I have now had my IS300H since April. Love almost everything about the car except for one small annoyance.

I can hear a tinny rattle from under the bonnet. On further inspection I have found the metallic heat shield over the exhaust manifold to be the culprit.

All the fixing bolts are tight but still the item moves about. I wonder if there should be some sort of fibre washers under the bolts to absorb any vibration.

Mentioned it yesterday when it was in for its annual service and first MOT. Lexus tech said it was normal !!! Seems a little odd that a quality product like Lexus would skimp on something so simple. That or the tech didn't want to touch it. Has anyone else seen this on their car?

Apologies if this has been discussed previously, but I cannot find any mention.

200h · August 25, 2016

mine is the same ,i was also suprised when i found this,its hard to take off as i think the exhaust goes through it.

i am going to get some clamping washers made at work but first i will have to draw some parts up

Alan Partridges Left Glove · August 25, 2016

Take it back, demand they show you what they class as the "normal" on another car in the showroom/forecourt.

This only backfires if the car you choose does the same.

I currently drive a Volvo V40 D4 RDesign which I've taken back with several issues but after leaving it with them I get the call to say they couldn't find anything but miraculously the issue has gone when I get the car back.

I'd prefer the honesty route and explain what they found and fixed rather than give me the same dribble response.

Hope you get it sorted I'm a tad OCD when it comes to rattles so I know where you are coming from.

200h · August 25, 2016

i am going to ask our engineering department and see if i can use some special plastics we have or wether stainless steel would be the better route.

Verbout · August 25, 2016

The wife complained of a rattle underneath her Seat Mii. I traced it to the exhaust heat shield.

I made some large square washers from sheet steel and covered them in mastic that I use on our log burner flue.

I put these washers between the bolts and the heat shield, about six I think.

Job jobbed.

martslexus · August 26, 2016

Thank you for all your replies. I have tried (in vain) to obtain a Lexus exploded view diagram to see if there is actually supposed to be additional washers here.

Looks like I might have to get fettling in the garage over w/e.

200h · August 26, 2016

tonight i had a eureka moment and after 5 minutes work the loose heat shield has gone

i had a bolt off a childs scooter that had quick release fittings ,the attached picture shows part of the quick release fitting.

remove a heat shield bolt and replace it with whats in the picture,

tighten the bolt up and the lip on the washer presses on the insert in the heat shield and clamps the insert to the shield.

jobs done

BaransuIS250 · August 31, 2016

On 8/26/2016 at 10:11 PM, 200h said:

tonight i had a eureka moment and after 5 minutes work the loose heat shield has gone

i had a bolt off a childs scooter that had quick release fittings ,the attached picture shows part of the quick release fitting.

remove a heat shield bolt and replace it with whats in the picture,

tighten the bolt up and the lip on the washer presses on the insert in the heat shield and clamps the insert to the shield.

jobs done

In March I bought an IS200T Premier and after the first few weeks I started hearing a very slight tinny sound from low rpm. It went in to my local dealer who said it was the fuel pump. I was quite shocked by this but had it done yet the noise persists. From reading the above i am sure it seems like it could also be the heat shield even though they initially checked this and said it was all fine. I wouldn't have thought the IS300H and 200T would have the same exhaust system but probably the same heat shield. The picture above looks more like a bolt to me- do you think you could post some of the other side of the bolt or an eBay link of a similarly sized item? I would really appreciate your help. Thanks!

200h · August 31, 2016

hi baransulS250 here are the images you wanted

capese21 · August 31, 2016

My previous IS had this seemingly loose heat shield. My present GS is the same. I was under the understanding that it was not meant to be fixed solid. Maybe it needs to allow for movement? I hear no noise from it so not worried. Personally I wouldn't bodge it with an old bolt. If it is noisy have it replaced.

200h · September 1, 2016

the bolt in my previous post doesn't stay in place it was only used to press the outer edge of the fixing onto the heat shield

the original bolt is then replaced,i dont know of any other car that has a loose heat shield on the exhaust system, every car i have

in the past have always had them fixed to the manifold securely .

steveo1973 · June 15, 2021

On 8/25/2016 at 2:52 PM, martslexus said:

I have now had my IS300H since April. Love almost everything about the car except for one small annoyance.

I can hear a tinny rattle from under the bonnet. On further inspection I have found the metallic heat shield over the exhaust manifold to be the culprit.

All the fixing bolts are tight but still the item moves about. I wonder if there should be some sort of fibre washers under the bolts to absorb any vibration.

Mentioned it yesterday when it was in for its annual service and first MOT. Lexus tech said it was normal !!! Seems a little odd that a quality product like Lexus would skimp on something so simple. That or the tech didn't want to touch it. Has anyone else seen this on their car?

Apologies if this has been discussed previously, but I cannot find any mention.

I have the same problem but mine doesnt rattle yet lol. The bolts are tight but the heat shield moves quite freely. Is it not just the case of untightening the two top bolts, adding a normal steel washer and tightening up?? hence the extra tension will then hold it in place?

Maybe its suppose to be loose, it might tighten up when it gets hot due to it expanding? I dont know.

Malc · June 15, 2021

Gentlemen, my elderly Ls400 once, a few years ago, had an irritating rattle over a certain road bump, just the one only, that puzzled me and my indy ............... discovered it was one of the heat shields .................. and that it was really really surplus to requirements on my car .... so off it came and in the bin ........ at many 10's of 000s of miles later all is well and fine ( she's on 232k miles now )

Maybe just check too see if your car really really needs it if you're going to go to the trouble of making it like new !

Malc