1998 XLE - grinding sound at 2200 RPM

[deadlyfalcon89]

Hi all,

As of about 2 days ago I'm experiencing a fairly odd phenomenon: When I accelerate through 2200 RPM I get a decently loud grinding noise coming from the right mid-rear of the car. The sound picks up about 2150 and stays through 2250, whereupon it disappears, or at least gets significantly quieter.

I took out the rear seat bottom and it's definitely louder (unsurprising) and I can actually feel the vibration if I put my hand on the metal under where the seat bottom normally is installed.

The noise only presents when I'm actually driving; that is to say, if I place the car in park and throttle up to 2200, the sound doesn't present.

About the car: 1998 XLE V6, 160,000 or so mostly highway miles, well maintained, normally sounds like a new car - very quiet.

About the circumstances of onset: had a good amount of rain (4" in 2 hours) so I ended up driving through some fairly deep water (figure 12" or so). However I can't recall whether or not I heard the noise prior to the storm.

After some research on the matter, I've come up with two things I think it might be:

1) Fuel pump. Only thing going against it is that the car seems to have the same throttle response/power it's always had. This would make sense given that the engine, under load, will pull more fuel at a given RPM than the engine at rest. Also, I'm not sure what sort of noise a dying fuel pump might make.

2) Catalytic converter. If this happened when I drove through the water, I may have heat-shocked the material inside the converter, which would lead it to crack. A given rate of exhaust might lead the cracked piece to vibrate, like blowing across a Coke bottle at the right rate/angle. However, I don't really know where the converter is, and I believe it's actually by the engine rather than the tailpipe.

3) (I lied) Muffler. This would follow a similar line of reasoning to the catalytic converter. Heat-shock something into cracking, harmonic frequency attained at an appropriate exhaust flow, etc.

I'd appreciate any thoughts on the matter; thanks so much!

[emiliorescigno]

If you need help I'd love to take a look at it, I'm always looking for cars to fix when I'm away from the Supras.

[ghettosled]

im guessing it has something to do with the exhaust. either a hanger is banging into the mount, a leak or even a bad heat shield. if the engine is under load, the exhaust can sound and shift differently.

[Chris Crash]

Is it a grinding noise? Like rocks in a tumbler? Or is it a rattling noise? Like tin cans tied to a string pulled behind the car?

Rattling would be exhaust. Grinding - you've got me. Either way I would check out the exhaust, as 4" of rain is rather much, hopefully you were'nt driving through any puddles that deep....

[deadlyfalcon89]

Alright, we looked at it yesterday and the noise is actually a rattling loose heat shield under the gas tank. So I have to either remove that or reattach the end that is loose - not sure if it rusted off or the bolts simply came undone. At least I can still drive the thing though.