What is this noise from - motor internals or what?

[shackelton]

I just replaced the rear motor mount which got rid of a nasty vibration/rattling when starting and at idle. All three (front motor mount and torque axis) motor mounts are new now.

I now have a "ringing" sound that appears to come from the front of the block just above or behind the exhaust manifold. It is present at idle and when revved up, when the motor is cold and at operating temperature. I removed both the p/s pump and alternator/A/C belt and started it up. The sound was still there so it's not belt whine.

This noise is not "mechanical" that is it doesn't sound like metal on metal. I attempted to remove the heat sheild from the manifold but the bolts are really rusted and will require soaking with penetrating oil before I can get the shield off. Still, I grabbed every part of the shield I could reach and shook it to see if it was loose or broken. It feels solid.

The sound is almost like metal resonating but is present at different RPM's.

Any ideas what this is?

1992 Camry LE 157K miles

Also, the flex pipe from the manifold is recent and is tight to the manifold.

Thanks

[karazy]

Does the pitch or volume change with RPM?
If you can get hold of a stethoscope (one from an automotive store with a long probe) it will make it much easier to trace.
I do vibration analysis on aircraft and everytime you try to stop a vibration in one place it will force that energy to another location, sometimes with a different frequency.
It could be timing belt related (bearing) or it could be a crack in something metal( bracket, manifold, etc...)

[amerikim]

readjust all your belts, could be your belt alignment.

[shackelton]

Originally posted by karazy
Does the pitch or volume change with RPM?
If you can get hold of a stethoscope (one from an automotive store with a long probe) it will make it much easier to trace.
I do vibration analysis on aircraft and everytime you try to stop a vibration in one place it will force that energy to another location, sometimes with a different frequency.
It could be timing belt related (bearing) or it could be a crack in something metal( bracket, manifold, etc...)

Yeah, the pitch increases/decreases with the engine RPM.

Thanks for the advice. I'll see where I can pick one up a stethoscope today.

I replaced the idler and tensioner pulleys when I did the timing belt in January 04.

I will readjust the belt tension too...I think I left the P/S belt a little too loose after I took it off (to rule it out) 'cause now the pump screeches when the wheel is turned all the way stop-to-stop....