I've searched through pages of threads but it seems like I have a slightly different problem. I hear what sounds like loose metal rattling from the engine bay. I've tried several things to diagnose the noise. Before searching I thought like everyone else and that it might just be a loose heat shield or something but the noise isn't constant. I know it's hard to diagnose something online so I'll try and be as specific as possible.

1) The noise is only present after it's been sitting for a while.
2) It only happens when the car is drive for the first 1-2 minutes at around 2k RPM.

I figured I'd let the car warm up a little longer so I let it run one morning for 15 minutes. Once I drove off I heard the rattle again. I don't hear a single thing when the car is in park and running even if i rev past 3k.

Any ideas as to what the sound may be? any help or guidance in the right direction would be greatly appreciated.

 

Use a hose or something that you can put to your ear and the other end of the hose to the engine compartment, see if you can pinpoint where its coming from. Not an easy thing to diagnose over the internet. Just gotta keep searching for where its coming from. I have a similar problem, took the hose to the compartment and narrowed it down to the water pump going out every case is different though.

 

Thanks for the advice, thing is it only makes the noise when the car is in drive and I accelerate so it makes narrowing down the noise more difficult. It also goes away after a minute or two so I can't even have a shop diagnose it. I'm going to see if I could upload a video. Otherwise, i'll see if it goes away after the 90k service.

 

bump for an answer/solution. I've had the same exact problem for 2-3 months now. I thought it might have been my water pump going bad also, but i just changed my timing belt/water pump/seals this past month. Unfortunately, I still had the problem after. I thought that maybe it could be a bad cat. convertor maybe?

 

Could be engine knock.

 

That would suck but more of reason for a swap lol. Doesn't sound like an engine knock, after a drive around the block the car sounds really healthy idling and the rattle stops. It only has 93k original miles but the previous owner did have it sitting for the past 5 years and rarely drove it. I already changed all the vital fluids too, transmission, differential, and engine oil of course.

 

Hmm, after my engine swap, I have a rattle - sort of a ticking or metallic type sound but it's only there around 1000rpm - so in park, if the car is cold then of course the idle is higher and I hear it - sounds as if it comes out of the bell housing under then car -

once the car is warm it idles lower and I don't hear it unless I rev it and hold it at 1000rpm - it's not a rod knock but sounds faintly reminiscent of one -

I can only think that maybe it's something in the tranny - I originally thought it was in the motor since you can hear it under the hood too - but it's not.

I took the serpentine belt off to rule out any accessories and the noise is still there.

Almost sounds like small marbles just rolling around.

 

My GS400 has developed this problem a few days ago. At idle it sounds like a rattling spray can, but its faint. As I give it throttle it gets louder but not to crazy. It almost sounds like a gatling gun but very raspy at full throttle. My theory is I have a cracked manifold passenger side and it's hitting the heat shield.

 

^mine does the same, sounds like something metal is loose and rattling/ but my car doesn't seem to have a problem driving or anything and it goes away when it's warm

 

OK guys I JUST HEARD another GS400 doing the EXACT same thing as my car at a stop light this morning - I wanted to stop the guy and ask!

I am guessing this is a fairly common issue - as I said, mine only does it at a "high" idle like in the morning - but the sound is always actually there at about 1000rpm

It goes away above and below that RPM and I know it's not a rod knock.

 

Hmm - that does not sound good at all - please update us on your noise as it's not the same as mine.

 

Today I went to the muffler shop. The guy found my converter was leaking at the flange that connects the manifold to it. Turns out it was just in place by the two bottom nuts secured. The upper most stud was stripped out with no nut. He eventually managed to remove the stud and put s new one in. He tested for exhaust leaks with a hose none found. So that leak is ruled out. The problem the rattling noise is still there. As I'm driving inside the cabin radio turned off complete silence windows up. I can hear the rattling noise sounds it's coming behind the A/C unit. When I roll my windows down I can't here it because my exhaust and noise outside mask it. It does sound like rattling marbles from that area center dash. So I got home popped the hood and all I heard is my fueling injectors clicking loud. I Think the rattling noise is resonating into the cabin making it heard to find. As I'm out side with the hood open I Rev the car using the throttle lever. The fuel injectors click louder. BTW I have a GS400. If anybody has found a solution to this noise please let me know.

The best way to describe the noise I'm hearing is. It sounds like a diesel trunk idling ticking noise. Though the noise increases as I'm pushing the accelerator. At idle it's there but very faint.

 

I'm wondering if motor mounts could be a cause? I might have lexus look at it in the future and see what they say

 

any updates?