Hey guys, recently I had my 1998 GS300 in the garage for a couple months due to a problem with the power steering. When I started it up to finally take it to the mechanic, I found a strange knocking sound that happens at idle. When I rev the engine, the knocking seems to go away, except for a groaning sound when I finally let off of the throttle. It sounds like it's coming from the engine bay, yet the mechanic couldn't find the source of it either. I figured I'd give some experienced Lexus owners a shot at diagnosing it, as it's very annoying and concerning. I uploaded a video to youtube of the sound in my engine bay.
Thanks, guys! I really appreciate it.

 

Remove the accessory belt and rev again, see if the noise is still present.

 

You mentioned you have power steering problems, so a bad power steering pump can make a knocking noise too, a loud embarrassing knocking noise. It's hard to know where the knocking is coming from in a video. Try to see if the noise is coming from there.

 

Thanks, I just got it replaced and it's working good... The sound sounds like it's coming from the area that I was pointing the camera at, the rear left of the engine

 

+1. Sounds like the belt is loose...remove it and see if the sound persists.

 

will do, thank you!

 

sure, thank you man! I'll be sure to try it out when I have the chance

 

Forgot to update this thread, but after all, it was my flex plate. It was completely cracked :,)

 

WOW!!! congratulations on updating the thread. I almost never see that. especially months later. glad your car is fixed.

 

Hopefully, someone will come across this with the same exact problem and finally have a solution. I couldn't find ANYTHING when I was searching the web so maybe this will show up somewhere!

One mechanic tried to tell me it was rod knock and my engine was going to break and offered to replace it, but I knew it was BS. Hopefully, nobody falls into that trap ...

 

Was odd when it started went away came back. From the video.

Thanks for sharing the solution.

 

We posted up this same issue somewhere else a while back. Same thing happened to me.
https://www.clublexus.com/forums/gs-...sion-area.html

 

That's from the flexplate spinning and somehow through centrifugal force stops knocking.