Buzzing/Metal Sound..WTH Is It..?

Hey guys, once again i got another little twitch that my car has now-after the accident in july. :banghead:

Every so often, like once a week/twice at best, when my car is sitting at idle-in PARK or neutral, i'll hear a buzzing/metalic like grating sound coming from the behind/bottom of the engine bay. It's coming from the area where the heat shields are and where the engine meets the tranny. The noise is loud enough to hear 5ft away from the car. :eek7:

I first thought this could be something in the trans..like buzzing from...i don't know..? But, i honestly cannot come to a conclusion. I took it to my mechanic today, he had no time to put it on the lift, and he just guestimated. :disappoin :screwy:

He told me, the way i got hit in the accident (other car hitting me dead on in the drivers wheel area@30mph) could be the culprit-and most likely it's something small like the heat shields on the exhaust-there are 2 heat shields in that area. He said by now, over the coarse of 5 months if it was something major it would have gotten MUCH worse. This is the same mechanic that guessed that my other car, had a bad heat shield.-below :lol:

Why would this happen only sometimes then...? I had a bad heat shield on a 92 ford escort, and that got BAD. This problem thank god didn't get worse since july/august. One other thing, if it's in park, and it's making the noise, if i rev it alittle-to like 1300K it'll go away, then come back when it's idling normally. It sparatically disappears also, the same day it was making the noise....crazy... :eek:

PS, Whats in that area that can make that noise..? Once again, this happened ONLY after the accident. :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead:

Sounds like heatshields to me too, Most of the time the bolts have deteriorated and are siezed in place so you cant tighten them. Common practice is to take large hose clamps and put them around the heat shield to tighten it, most of the time this stops the rattle.

Someone told me in the thunderbird forum about an epc.

Then i looked up epc solenoid, and found out alot of people have the same sound. The thing is, i forgot to mention, a week and a half before my accident, i had avis do a complete flush/refill of my tranny and torque converter. Everything was fine, no problems-until after the accident.

If it ain't gotten worse in 5 months, it has to be something small.....i hope... :-(

A problem i had with my nisan this summer made a similar sound, though it did it under no load and light load conditions. I put it up on the lift at work and started banging around with a mallet until i found the culprit. There was a expansion/resonance (what do you call these things) chamber halfway down the exhaust that had a rattle inside. I ended up having to cutout the rust and bolts between the flanges and found that a plate inside had come loose (thanks for the genious design nissan.) the piece was to big to pull out, so we just brazed it back into place. It has been fine fora good seven months now.

I'm gonna get this on the lift hopefully the end of the day, i'll tell yall what it was...if we can find it:-(

Lol, to funny.

I go to the mechanic.....NOISE GONE.....

Anyway, we get it on the lift, and there is NO noise. So he gets a tiny plastic mallet, and begins to tap the exhaust lines..sure enough, it was the passenger heat shield on the cat. It was in good condition, but the upper portion was rusted and looked like it was just barely rubbing the exhaust.

So for nothing, he put on a big metal tie down to compress it. No noise so far......

Hum... seems like I'v heard that somewhere before.