Hi all

I've been lurking here for months now but this is my debut post so be gentle!

Last week I got the water pump on my 190e replaced the mechanic doing the work phoned me up after he'd done the job wondering if the serpentine belt had been squeeking before
at all. I said no, he said it was now and that he'd try to get working properly. When I picked the car up it was nice and quiet
so both of us thought he'd done the job. On the way home a twittering noise started to appear it got louder and varied with the engine speed.

I took off/refitted the belt myself on Friday but it made no difference. I briefly ran engine without belt and all was quiet.

On the first start of the day its fine for about 10 seconds then the sound appears quietly at first before finding its full voice which stays heard until the engine is turned off.

The pump seems to be working fine no leaks, engine temp steady. So I'm now wondering what the cause of the noise is - the belt, the pump, something else again....

Just re-cap the noise sounds like a twittering or chirping bird.

Any ideas?

Mike.