engine grinding/rattle above 4k rpm

[calreef18]

Hello everyone, I recently purchased a 97' gst spyder, its a nice car and I started purchasing some mods, I got a boost gauge thus far. One problem that I've noticed is the car is fine under light/medium acceleration, but above 4k, I hear a grinding from the engine bay from around 4k-6.5k rpm. Any guesses as to what the noise could be? Car has 133k, but was rebuilt 6k miles ago.I'm gonna try and free rev and maybe discover the culprit. Seems to be coming from the engine when I had a friend rev for me. Does it need balancing? Anything I should try and look for? Thx.

 

[xioca]

Check your motor mounts, mine were worn out and torn and made a a grinding noise from 4k+.

 

[calreef18]

Thx gonna try that.

 

[andymoraitis]

Rattles and such are hard to diagnose without a sound clip or hearing it firsthand. The most prudent thing to do is isolate where the noise is coming from (i.e. valvetrain, top of the motor, bottom of the motor, etc.). A few common spots to check depending on location are:

1. Separated crank pulley (this will make a knocking sound).
2. Loose valve cover baffles (pull the VC and see if any of the baffles can be moved)
3. Loose exhaust heat shields (upper and lower)
4. Exhaust rattles
5. Failing timing belt tensioner

Regarding the crank pulley, you'll need to remove the driver's side wheel and inner splash guard to see it. Have a look and inspect it if your noise seems to be coming from that area.

If the sound seems to be internal, it wouldn't be a bad idea to invest in a mechanic's stethoscope to isolate the noise more accurately.

Good luck and keep us posted,

Andy

 

[calreef18]

Thanks everyone, I'll try to get a sound clip if possible. The sound sorta is like a metal fan blade scraping against a hard object, and past 4k the sound is off and on, and sometimes barely at all. Gonna try and pinpoint it tomorrow, if not I'm gonna try and take it into a shop and see what they say.

 

[JiveMasterT]

Yeah we definitely need a sound clip if possible. That could be 100 different things.

 

[calreef18]

Lol, can't hear anything in the recording I tried to make, the camera phone just picks up the loudness of the engine. I checked 3 motor mounts and they seemed fine, except the driver side one was cracking but still seemed to be ok. I revved the car with the hood open and listened for the rattle, couldn't hear it anywhere in the bay really which is good,but when I went inside I could. I went under the car and it seemed to be coming from something before the cat. I'll try to investigate further, seems to be a heat shield possibly or something metal and loose just rattling.

Edit- took the battery off, there's a little canister underneath that had a clamp that wasn't tightened down. Fixed it and the rattle isn't really there anymore. Good stuff,thanks everyone. Now if I could just get my new bov, mbc, and intake.