IS300H F-Sport thumping dumping noise from rear

Poolmane · May 7, 2022

Hi friends,

I have a IS300h F-Sport (from 2017, about 47000km on it) since last year. Sadly I have a thumping dumping sound from rear.

I'm trying to describe it: when I'm driving on a road that is slightly bumpy or not brand new, I hear a dull rumble from behind. Especially at slow speeds.

It is not a rattle or a metal sound. It is a clean dull muffled knock/bump. Everytime it's the same noise with the same volume.

A month ago I was at service and addressed this. They could hear it but they couldn't find anything and said it's normal. That drives me crazy! I looked through various forums in Germany but couldn't find any help .

The error occurs with both summer tires and winter tires. The vehicle is completely original.

Additionally i sound deaded the whole car, which makes it super quiet and comfy but the thump bump bump bump at lower speed destroys the experience.

I appreciate all your help and I tied to discribe the problem properly.

Sorry for my slight bad English 😄
Thanks a lot and best wishes from Germany

Timo

Tel · May 8, 2022

Spare wheel loose ?

Tel

Poolmane · May 8, 2022

I didn't have a spare wheel it's a hybrid

Mincey · May 8, 2022

1 hour ago, Tel said:

Spare wheel loose ?

Tel

It's a can of gunge in an IS300h, not a spare wheel unfortunately. I had a rattle/bang in my '99 IS200 and it took the dealer ages to pinpoint the cause. They never told me what it was though.

CypressPhil · May 8, 2022

If it’s a rumbling noise rather than a knocking, it could be a wheel bearing maybe? It will sound like a low growl/rumble and will be more noticeable at certain speeds. If it’s a knocking, then it could be a suspension bush but I’d have thought they’d have picked that up on the service.

PaulWhitt20 · May 8, 2022

I think I have this issue too. Had it for a few years. I have not got Lexus to investigate but nothing has fallen off yet. I did mention it at the last service but they didn’t report anything. I have not investigated further as it means taking a day off work to get it to the dealer.

Poolmane · May 9, 2022

It's more a clean muffled knock noise when the suspension is working.

PaulWhitt20 · May 9, 2022

Check the spare wheel gunk is fixed tightly to the top of the Battery and the jack is in tight. mine was a bit loose and it seems better now.

Now just need to sort the squeak at low speeds.

Spock66 · May 9, 2022

I'd say either the suspension or maybe the exhaust.

Poolmane · May 9, 2022

4 hours ago, PaulWhitt20 said:

Check the spare wheel gunk is fixed tightly to the top of the battery and the jack is in tight. mine was a bit loose and it seems better now.

Now just need to sort the squeak at low speeds.

Hey, as I said I have a hybrid and there is no spare wheel.

i I really can't imagine that something on the chassis/suspension is defective. I mean the vehicle has just run 47000km.

Spock66 · May 9, 2022

13 minutes ago, Poolmane said:

I really can't imagine that something on the chassis/suspension is defective. I mean the vehicle has just run 47000km.

Brand new cars can have faults, if you discount this as a possibility without evidence you narrow down the possibility of finding the problem.

PaulWhitt20 · May 9, 2022

29 minutes ago, Poolmane said:

Hey, as I said I have a hybrid and there is no spare wheel

Left hand side of the boot, their is a pull away cubby hole where the 12V Battery is located. On top of this their should be the puncture repair kit (Gunk, jack etc). This is strapped down with a "rubber band". Check this is secure and the Gunk etc is not bounding up and down on the Battery.

Hope that helps

Paul

Poolmane · May 11, 2022

On 5/9/2022 at 9:49 AM, PaulWhitt20 said:

Check the spare wheel gunk is fixed tightly to the top of the battery and the jack is in tight. mine was a bit loose and it seems better now.

Now just need to sort the squeak at low speeds.

The spare wheel gunk i since 3 weeks on the right side of the trunk. That's not the fault.

I upgrade the Battery to 55ah 12v custom Battery so that there is no more space for the wheel gunk.

But thank you for your suggestions 🙂

Poolmane · May 11, 2022

On 5/9/2022 at 2:53 PM, Spock66 said:

Brand new cars can have faults, if you discount this as a possibility without evidence you narrow down the possibility of finding the problem.

The car handles very good. Since I have the knock sound from beginning there is no fault with the handling. I have a safety training with the car and it was the "best" in the round of other cars. It handles very good.