Weird Rattle

[Tbay LX]

Hey guys,
My 98 LX 470 seems to have developed some sort of strange metallic rattle noise. I'm hoping that it is the well known heat shield issue, however mine seems a little different. It seems to occur largely while I'm at a stop. If I'm in park, and push hard on the break pedal, it it really kicks in. Any ideas if this could be something else, or am I best to crawl under the truck and just start banging on the exhaust system?

 

[TXLX100]

I think I had this exact same thing on my 1998 a while back. When first starting up and pulling down the incline of my driveway forward, if I braked hard at the bottom of the drive there was about a 1-2 second metallic humming from the front or front right. My guess is it was something with the AHC trying pump back up quickly from the drop in the front end on an angle. Whatever it was, it went away on its own.

 

[Tbay LX]

I think I had this exact same thing on my 1998 a while back. When first starting up and pulling down the incline of my driveway forward, if I braked hard at the bottom of the drive there was about a 1-2 second metallic humming from the front or front right. My guess is it was something with the AHC trying pump back up quickly from the drop in the front end on an angle. Whatever it was, it went away on its own.

Interesting, I was wondering if it could have to do with the AHC. Hopefully it will go away on its own as yours did.

 

[consalvochris]

Cut off your catalytic heat shields! Mine made the same sound. I tried using a clamp to hold them down but they came loose over time. It is better to just remove them and forget out it. Any automotive shop will do this for cheap, or just get under there with a angle grinder. I would not start trouble shooting expensive systems like AHC until you rule out the shields.

 

[Tbay LX]

No risk in removing them? It looks like there are some rocks in mine. I can't get them out though...

 

[hoser]

It seems to occur largely while I'm at a stop. If I'm in park, and push hard on the break pedal, it it really kicks in.

Well, that sounds like it should be easy to find. I had a rattling sound that could only be heard occasionally, at 10-15mph and in Drive.

 

[DJWUZJ]

Try taking the cover off the engine first. I went through the same process of elimination, until I finally popped it off and cured the sound. While it is made out of plastic, it gives a metallic sound when rattling.

It just never seated right after the 90k service. She runs naked now.