Toyota Echo noise

I have a 2001 Toyota Echo with 47,000 miles. Car runs great, except for an intermittent high pitched chirping noise which is most evident when the car is warmed up & on the highway however noise disappears when I slow down to under 40 or apply brake @ any speed. Checked under the hood when it happened on the road, but no smell, smoke, unusual engine compartment noise, or dashboard lights;car runs normally. Mechanic says all is ok, including serpintine belt. Help.

I would want to take another look at the accessory belt and all the bearings it is turning. Vacuum pump?

The fact that the noise stops when you apply the brakes makes me think it’s coming from the brakes.

Where does the noise seem to be coming from? Under the hood, under the car, or under the dashboard? Front or rear, left or right? Be as specific as possible.

Difficult to pinpoint but seems to becoming from beneath the car, below the drivers seat or slightly forward. Otherwise, even with noise car runs normally. Nothing unusual under the hood with engine running. Brake pads replaced in August 2008.Thanks.

Vehicle runs normally, I & mechanic checked belt & all seems ok. But why does it only happen on highway & after warmed up? Thanks.

Did this occur before the new brakes? I would have the front brake pads and rotors checked.

It’s possible the brake tech didn’t reset the position of the brake pad wear tab.

Are these tabs attached directly to the pads these days?

My first thought was bearings, too. And I agree to get brakes rechecked. But why would either of these issues cease when under 40 mph?? Here’s an idea. Next time the car is warmed up and you’re on the highway, take an exit ramp and pull over somewhere and lift the hood with car running. Listen for noises. Then open the throttle to similate being over 40mph and see if you hear the noise. It might help you to pinpoint where the noise is comming from if you can hear it while standing there. Otherwise, I’d check the brakes out - should be under warranty still.