jyeung528

I am hearing a noise when I am at a stop.

It sounds like a computer's power supply turning on when you switch your computer on.

What I hear is the noise switch on, and then it immediately switches off, like a computer turning on, and off. It comes from the front left of the engine bay if you are sitting in the driver's seat.

Any idea what this sound can be? A problem or just normal?

At the same time, it occurred to me that I haven't heard my radiator fan turn on for a long time. Could this be a related problem where the sound is the radiator fan trying to switch on, but it is not?

Also, if you standing outside and open the hood...the radiator fan is to the right...what is the fan on the left?

Thanks for any help.

Jeff

milkbubble

If its coming from the front left of your car I would say its your air pump. Its part of emissions systems. When you start your car cold do you hear it make a whirring noise for a little bit? What it does is introduce more air into your intake on a cold start so that your 02 sensor can reach normal operating temperature. It helps the heating element in the sensor do its job and that is to reach 600 degrees fareheight.

Slows2k

It's not to heat up the 02, but to add extra oxygen to heat up the convertor.

The noise is the air pump and it's very normal.

4bang6

milkbubble

Yeah my bust.. my mind was on the 02 sensor because i was out back drilling out a antifouler.. LoL!

More oxygen => lean => higher temps => more efficient cat during open loop etc.