2002 Is300 Rear Rhs Knocking Noise- Can't Diagnose?

[jakirk]

Hi guys,

I've got a 2002 IS300 I purchased about 5 months ago. It's currently got about 67,500kms on the clock. I bought it with about 60,000kms on the clock. About a month or so I noticed a knocking type noise developing in the rear right hand side. It was weak at first, but progressively got worse. I've tried to diagnose it, and taken it to both an independent mechanic and Lexus dealer, and they don't know what the problem is.

HISTORY

When I purchased the car, a pre-purchase check revealed a leaking stock right hand side shock absorber. I shaved the replacement cost off the purchase price and bought it. After about a month the noise developed, and I assumed it was the shock running out of fluid and causing the noise.

I booked it in for a replacement with after market parts at my local Ultra Tune (I know, Ultra Tune, but I know the guy there from a while back). They replaced both rear shocks, and the noise was gone. I assumed this was the problem and was happy it was fixed.

About 2 months later the noise came back. Over the course of about 2 weeks I heard it slightly again, and then it was back to what it had been before the shock replacement. I thought it was a suspension problem.

A guy I work with who owned a 2000 Altezza he drifted from time to time sat in the car with me, and in his opinion it doesn't sound like a suspension noise. He thought it might be the exhaust or a sway bar link that had worn out.

I brought it back to the same mechanic, who couldn't figure it out after spending a few hours trying to diagnose the problem. I decided to take it to a dealer. The dealer (Lexus of Blackburn in Melbourne) had the car for a day and could not figure it out. They've asked me to bring it back which I'm reluctant to do.

DIAGNOSIS

It is most noticeable at low speed, particularly when going over tram tracks or something similar- but I've even noticed it on very smooth surfaces now like under ground car parks.

It's most evident on 'take offs', when the car goes from being stationary to moving, but if accelerating quickly its not very noticeable (perhaps due to engine and environment noise). If the car is stationary for extended periods (ie. parked over night or for a few days) the noise won't be immediately evident.

I've checked the exhaust. I'm not that experienced with fixing cars, but I know some basics. I've also had my brother check it out, who knows a fair bit from building a couple rally cars. He's unsure of what it is either.

SAMPLE

Here's a sample of the noise: http://www.mediafire.com/?386tbczy250x6n4.

I only have my iPhone available, so sorry about the quality and volume. But you get a pretty good idea of the noise. The phone was sitting on the back right seat (behind the driver) when driving on Tram Tracks.

If anyone can help, has had a similar problem, or seen a similar problem, would be greatly appreciated.

Thanks guys