Derb

I'm hoping someone can suggest some causes for a noise from my Fiesta. It's like a faint whistling, almost like a kettle, almost like just hissing through your teeth, going up and down a bit. It only does it when it's warmed up, and when you stop and lift up the bonnet, it seems to come from the general area of the drivers side, but will usually stop before I can get a wooden stick out and try to locate it (you know, by using the stick as a sort of stethoscope). Apparently random things seem to set it off, like turning a corner, braking, or pressing the clutch. So as far as I know it seems to depend on some delicate equilibrium of electrical current, momentum, or engine speed (i.e. just about anything, really). I replaced the auxiliary belt (with a new one), and the alternator (with a good one I had lying around), and it's still there. Could the water pump or PAS pump make this sort of noise? Or an air leak?

bigjohn0

There is a idler pully on the belt and usually they are at fault. Its the one with a single bolt through it and is bolted onto the engine mount housing. Ebay is the best place to get one

Derb

I was thinking that as I looked at it a few weeks ago. But what I thought was the idler pulley turned out to be a wheel on the end of the water pump. It turns out that this model doesn't have an idler pulley at all.