everytime i rev at like 3000 rpm, i hear this grinding noise..i am unable to tell wher eexactly its coming from but it sounds like from the bottom of the car. i have a 2000 civic si with 48000 miles.

 

I had a GSR with the exact same problem. I couldn't figure it out for the life of me. Please, in detail. describe this noise the best you can and perhaps I can help you.

Kyle
B.S. Biochemistry/Cellular Molecular biology/Biophysics
Synthesis of Potassium bis(2-hydroxyethyl)dithiocarbamate
Retired master mechanic

 

excuxe the . where there was supposed to be a ,

 

it sounds like a scraping noise..could it possibly be that exactly at 3000 rpm my flywheel its catching? any help?

 

First I suppose you can check all your exhaust heat shields, just to eliminate that as a possibility. Mounting hardware rusts & falls apart, then the shields buzz & rattle against each other & against the exhaust pipe. Crawl under & start banging stuff with your fist until you find something loose.

Then maybe it's the famous buzzing A-pipe. I don't know about the SI, but for the GSR it's like this... The A-pipe (from exhaust manifold, under oilpan, to cat) is really a pipe-inside-a-pipe. It either warps a bit or comes loose, then the inner pipe buzzes against the outer one. That A-pipe is real expensive so it's a good excuse to buy a header.

 

never heard of this before but it sounds to me like it could be the header or exhaust or the exhaust manifold if u still have one.