Tambourine when cold

Just done 800 miles in the 05 TF with no trouble.
However, when the car is cold, it sounds like someone is rattling a tambourine close the the offside rear wheel.
The noise is linked to engine speed and disappears when the water temp is up (max. 5 minutes).

My suspicion is water pump. Any other suggestions welcome.
Thank you.

Could also be the alternator? They can squeal when under load. It stops once the current demand has dropped.

Check the drive belt, it could be slipping 

I new a chap who complained about a humming, an almost tuneful sound above 30MPH.
It became unbearable at speeds over 50 & no one could get to the bottom of the problem to a point where he decided to get rid of the car, a car which until then, he adored.
Then all of a sudden, just as strangely as it started, it stopped.
A short time later he found a crushed harmonica on the drive; some “mates” had double sided sticky taped it to the underside of his car.
M

Appreciate the suggestions.
Oddly, today, almost no rattling. Will keep an eye on it.

If it is under the belt cover, it will be my first foray there.....

AP, definitely not in the woodwind family. I'll check my castanets though, in case I mistakenly taped them to the wheel arch..

 

I was referring to the poly rib auxiliary drive belt.... the one that drives the alternator

Airportable wrote:

I new a chap who complained about a humming, an almost tuneful sound above 30MPH.
It became unbearable at speeds over 50 & no one could get to the bottom of the problem to a point where he decided to get rid of the car, a car which until then, he adored.
Then all of a sudden, just as strangely as it started, it stopped.
A short time later he found a crushed harmonica on the drive; some “mates” had double sided sticky taped it to the underside of his car.
M
I like that, there is an old harmonica lurking about here somewhere, all I need to do is find that and a victim!
 

As an update, the tinkling continued.
Looking around, the aux belt seems to be the problem (as Cobber mentioned).
It was not slipping but vibrating until warmed up. A squirt of WD40 as a test stopped it immediately.
A new aux belt is on order.

Thanks gents & Cobber.

Just replaced my auxiliary belt and found the tensioner pulley bearings were shot. The pulley rattled around something awful!
Might be worth checking that too - the belt will not run true if the pulley isn't running straight.

AUTF02, was it the timing belt that you changed and found the tensioner or the alternator belt? I thought there was no tensioner on the alternator belt?
We sprayed the alternator belt with the engine running and that stopped the rattling.

Mine is a 2002 TF and definitely has a tensioner pulley associated with the alternator (ancillary) belt.
It has air con & don't know if that makes a difference. 

Ah, aircon. That's the difference. No aircon is a straight loop.
Thanks for letting me know. I would have thought mine had fallen off!