My 2006 1.6tdci focus has developed a very high pitched whistle within the last mile or so. I have a recording which I'll post later when back home. The whistle started out of nowhere, and is always present. At idle, it is very quiet, and increases in both pitch and volume as revs go up. After about 2k revs, i assume its still there but engine noise takes over.
A quick Google search has suggested either a split pipe somewhere, auxiliary drive belt or the alternator. I opened the bonnet and, with the engine running, felt a warm draft in one place, near where a pipe meets the front of the engine. I'm unsure of whether this is normal or not.
Any ideas of what it could be?
Thanks in advance,