Strange whirring sound coming from my 2004 Yaris 1.33 petrol?

raptor2004

Hi all, I have a 1st generation Toyota Yaris petrol. 

I have noticed a low pitched whirring sound that constantly sounds as I drive off. The level remains consistent as I accelerator but goes off as I come to a stop/idle. It doesn't matter if I am in gear or not when the car is in motion, the noise is always there.

I should mention that the noise started ever since I got a brake fluid change over the weekend, but I don't notice any difference in stopping power. 

I had the battery replaced earlier this year by RAC and the mechanic mentioned that my alternator is noisy and may need replacing soon. The garage over the weekend checked the auxiliary belt and said it appeared to be in okay condition (no rips).

Any idea what it could be? I thought it might be the water pump but that'll also make a noise when the engine is idling too.

Goudy

Difficult to tell from here but by the sounds of it, the garage stating the alternator is making the noise is probably the biggest clue.
The bearings in it are probably shot or the belt tensioner is shot.

There are a couple of ways to test it.
One would be to carefully hold a screwdriver to the alternator body then tensioner body when the engine is running, any rumblings or grumblings would be fed back through the screwdriver handle.
I say carefully, you need to steer clear of the moving belt.

Another would be just to remove the aux belt and run the engine up, but I believe the water pump is ran off the same belt on these engines, so if that is what is grumbling instead of the alternator or tensioner, you wouldn't know which. 

raptor2004

Update:

Took the car to the same garage that did the engine oil and brake fluid change. They said the the noise is coming from the front brakes and that the discs and pads need to be changed. They said its not urgent, I can still drive (so long I can bear the noise) but to change it as soon as I am able to. I have done about 800 miles since and the noise has gone away itself!

I am aware that they will need changing and I will do it within the next month or so.

I was worried it was the auxiliary belt and/or water pump but luckily not. Was a bit of a struggle to drive in the summer heat as the car does not have AC and I often do 150 mile trips twice a week but as we are heading into autumn and winter I think I will keep the car a little longer. It is a good old banger